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  • Speakers, Please Check Your Time

    - by AjarnMark
    Woodrow Wilson was once asked how long it would take him to prepare for a 10 minute speech. He replied "Two weeks". He was then asked how long it would take for a 1 hour speech. "One week", he replied. 2 hour speech? "I'm ready right now," he replied.  Whether that is a true story or an urban legend, I don’t really know, but either way, it is a poignant reminder for all speakers, and particularly apropos this week leading up to the PASS Community Summit. (Cross-posted to the PASS Professional Development Virtual Chapter blog #PASSProfDev.) What’s the point of that story?  Simply this…if you have plenty of time to do your presentation, you don’t need to prepare much because it is easy to throw in more and more material to stretch out to your allotted time.  But if you are on a tight time constraint, then it will take significant preparation to distill your talk down to only the essential points. I have attended seven of the last eight North American Summit events, and every one of them has been fantastic.  The speakers are great, the material is timely and relevant, and the networking opportunities are awesome.  And every year, there is one little thing that just bugs me…speakers going over their allotted time.  Why does it bother me so?  Well, if you look at a typical schedule for a Summit, you’ll see that there are six or more sessions going on at the same time, and only 15 minutes to move from one to another.  If you’re trying to maximize your training dollar by attending something during every session time slot, and you don’t want to be the last guy trying to squeeze into the middle of the row, then those 15 minutes can be critical.  All the more so if you need to stop and use the bathroom or if you have to hike to the opposite end of the convention center.  It is really a bad position to find yourself having to choose between learning the last key points of Speaker A who is going over time, and getting over to Speaker B on time so you don’t miss her key opening remarks. And frankly, I think it is just rude.  Yes, the speakers are the function, after all they are bringing the content that the rest of us are paying to learn.  But it is also an honor to be given the opportunity to speak at a conference like this, and no one speaker is so important that the conference would be a disaster without him.  Speakers know when they submit their abstract, long before the conference, how much time they will have.  It has been the same pattern at the Summit for at least the last eight years.  Program Sessions are 75 minutes long.  Some speakers who have a good track record, and meet other qualifying criteria, are extended an invitation to present a Spotlight Session which is 90 minutes (a 20% increase).  So there really is no excuse.  It’s not like you were promised a 2-hour segment and then discovered when you got here that it was only 75 minutes.  In fact, it’s not like PASS advertised 90-minute sessions for everyone and then a select few were cut back to only 75.  As a speaker, you know well before you get here which type of session you are doing and how long it is, so as a professional, you should plan accordingly. Now you might think that this only happens to rookies, but I’ll tell you that some of the worst offenders are big-name veterans who draw huge attendance numbers for their sessions.  Some attendees blow this off as, “Hey, it’s so-and-so, and I’d stay here for hours and listen to him/her talk.”  To which I would reply, “Then they should have submitted for a pre- or post-conference day-long seminar instead, but don’t try to squeeze your day-long talk into a 90-minute session.”  Now I don’t really believe that these speakers are being malicious or just selfishly trying to extend their time in the spotlight.  I think that most of them are merely being undisciplined and did not trim their presentation sufficiently, or allowed themselves to get off-track (often in a generous attempt to help someone in the audience with a question or problem that really should have been noted for further discussion after the session). So here is my recommendation…my plea, even.  TRIM THE FAT!  Now.  Before it’s too late.  Before you even get on the airplane, take a long, hard look at your presentation and eliminate some of the points that you originally thought you had to make, but in reality are not truly crucial to your main topic.  Delete a few slides.  Test your demos and have them already scripted rather than typing them during your talk.  It is better to cut out too much and end up with plenty of time at the end for Questions & Answers.  And you can always keep some notes on the stuff that you cut out so that you could fill it back in at the end as bonus material if you really do end up with a whole bunch of time on your hands.  But I don’t think you will.  And if you do, that will look even better to the audience as it will look like you’re giving them something extra that not every audience gets.  And they will thank you for that.

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  • Cloud to On-Premise Connectivity Patterns

    - by Rajesh Raheja
    Do you have a requirement to convert an Opportunity in Salesforce.com to an Order/Quote in Oracle E-Business Suite? Or maybe you want the creation of an Oracle RightNow Incident to trigger an on-premise Oracle E-Business Suite Service Request creation for RMA and Field Scheduling? If so, read on. In a previous blog post, I discussed integrating TO cloud applications, however the use cases above are the reverse i.e. receiving data FROM cloud applications (SaaS) TO on-premise applications/databases that sit behind a firewall. Oracle SOA Suite is assumed to be on-premise with with Oracle Service Bus as the mediation and virtualization layer. The main considerations for the patterns are are security i.e. shielding enterprise resources; and scalability i.e. minimizing firewall latency. Let me use an analogy to help visualize the patterns: the on-premise system is your home - with your most valuable possessions - and the SaaS app is your favorite on-line store which regularly ships (inbound calls) various types of parcels/items (message types/service operations). You need the items at home (on-premise) but want to safe guard against misguided elements of society (internet threats) who may masquerade as postal workers and vandalize property (denial of service?). Let's look at the patterns. Pattern: Pull from Cloud The on-premise system polls from the SaaS apps and picks up the message instead of having it delivered. This may be done using Oracle RightNow Object Query Language or SOAP APIs. This is particularly suited for certain integration approaches wherein messages are trickling in, can be centralized and batched e.g. retrieving event notifications on an hourly schedule from the Oracle Messaging Service. To compare this pattern with the home analogy, you are avoiding any deliveries to your home and instead go to the post office/UPS/Fedex store to pick up your parcel. Every time. Pros: On-premise assets not exposed to the Internet, firewall issues avoided by only initiating outbound connections Cons: Polling mechanisms may affect performance, may not satisfy near real-time requirements Pattern: Open Firewall Ports The on-premise system exposes the web services that needs to be invoked by the cloud application. This requires opening up firewall ports, routing calls to the appropriate internal services behind the firewall. Fusion Applications uses this pattern, and auto-provisions the services on the various virtual hosts to secure the topology. This works well for service integration, but may not suffice for large volume data integration. Using the home analogy, you have now decided to receive parcels instead of going to the post office every time. A door mail slot cut out allows the postman can drop small parcels, but there is still concern about cutting new holes for larger packages. Pros: optimal pattern for near real-time needs, simpler administration once the service is provisioned Cons: Needs firewall ports to be opened up for new services, may not suffice for batch integration requiring direct database access Pattern: Virtual Private Networking The on-premise network is "extended" to the cloud (or an intermediary on-demand / managed service offering) using Virtual Private Networking (VPN) so that messages are delivered to the on-premise system in a trusted channel. Using the home analogy, you entrust a set of keys with a neighbor or property manager who receives the packages, and then drops it inside your home. Pros: Individual firewall ports don't need to be opened, more suited for high scalability needs, can support large volume data integration, easier management of one connection vs a multitude of open ports Cons: VPN setup, specific hardware support, requires cloud provider to support virtual private computing Pattern: Reverse Proxy / API Gateway The on-premise system uses a reverse proxy "API gateway" software on the DMZ to receive messages. The reverse proxy can be implemented using various mechanisms e.g. Oracle API Gateway provides firewall and proxy services along with comprehensive security, auditing, throttling benefits. If a firewall already exists, then Oracle Service Bus or Oracle HTTP Server virtual hosts can provide reverse proxy implementations on the DMZ. Custom built implementations are also possible if specific functionality (such as message store-n-forward) is needed. In the home analogy, this pattern sits in between cutting mail slots and handing over keys. Instead, you install (and maintain) a mailbox in your home premises outside your door. The post office delivers the parcels in your mailbox, from where you can securely retrieve it. Pros: Very secure, very flexible Cons: Introduces a new software component, needs DMZ deployment and management Pattern: On-Premise Agent (Tunneling) A light weight "agent" software sits behind the firewall and initiates the communication with the cloud, thereby avoiding firewall issues. It then maintains a bi-directional connection either with pull or push based approaches using (or abusing, depending on your viewpoint) the HTTP protocol. Programming protocols such as Comet, WebSockets, HTTP CONNECT, HTTP SSH Tunneling etc. are possible implementation options. In the home analogy, a resident receives the parcel from the postal worker by opening the door, however you still take precautions with chain locks and package inspections. Pros: Light weight software, IT doesn't need to setup anything Cons: May bypass critical firewall checks e.g. virus scans, separate software download, proliferation of non-IT managed software Conclusion The patterns above are some of the most commonly encountered ones for cloud to on-premise integration. Selecting the right pattern for your project involves looking at your scalability needs, security restrictions, sync vs asynchronous implementation, near real-time vs batch expectations, cloud provider capabilities, budget, and more. In some cases, the basic "Pull from Cloud" may be acceptable, whereas in others, an extensive VPN topology may be well justified. For more details on the Oracle cloud integration strategy, download this white paper.

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  • Cloud to On-Premise Connectivity Patterns

    - by Rajesh Raheja
    Do you have a requirement to convert an Opportunity in Salesforce.com to an Order/Quote in Oracle E-Business Suite? Or maybe you want the creation of an Oracle RightNow Incident to trigger an on-premise Oracle E-Business Suite Service Request creation for RMA and Field Scheduling? If so, read on. In a previous blog post, I discussed integrating TO cloud applications, however the use cases above are the reverse i.e. receiving data FROM cloud applications (SaaS) TO on-premise applications/databases that sit behind a firewall. Oracle SOA Suite is assumed to be on-premise with with Oracle Service Bus as the mediation and virtualization layer. The main considerations for the patterns are are security i.e. shielding enterprise resources; and scalability i.e. minimizing firewall latency. Let me use an analogy to help visualize the patterns: the on-premise system is your home - with your most valuable possessions - and the SaaS app is your favorite on-line store which regularly ships (inbound calls) various types of parcels/items (message types/service operations). You need the items at home (on-premise) but want to safe guard against misguided elements of society (internet threats) who may masquerade as postal workers and vandalize property (denial of service?). Let's look at the patterns. Pattern: Pull from Cloud The on-premise system polls from the SaaS apps and picks up the message instead of having it delivered. This may be done using Oracle RightNow Object Query Language or SOAP APIs. This is particularly suited for certain integration approaches wherein messages are trickling in, can be centralized and batched e.g. retrieving event notifications on an hourly schedule from the Oracle Messaging Service. To compare this pattern with the home analogy, you are avoiding any deliveries to your home and instead go to the post office/UPS/Fedex store to pick up your parcel. Every time. Pros: On-premise assets not exposed to the Internet, firewall issues avoided by only initiating outbound connections Cons: Polling mechanisms may affect performance, may not satisfy near real-time requirements Pattern: Open Firewall Ports The on-premise system exposes the web services that needs to be invoked by the cloud application. This requires opening up firewall ports, routing calls to the appropriate internal services behind the firewall. Fusion Applications uses this pattern, and auto-provisions the services on the various virtual hosts to secure the topology. This works well for service integration, but may not suffice for large volume data integration. Using the home analogy, you have now decided to receive parcels instead of going to the post office every time. A door mail slot cut out allows the postman can drop small parcels, but there is still concern about cutting new holes for larger packages. Pros: optimal pattern for near real-time needs, simpler administration once the service is provisioned Cons: Needs firewall ports to be opened up for new services, may not suffice for batch integration requiring direct database access Pattern: Virtual Private Networking The on-premise network is "extended" to the cloud (or an intermediary on-demand / managed service offering) using Virtual Private Networking (VPN) so that messages are delivered to the on-premise system in a trusted channel. Using the home analogy, you entrust a set of keys with a neighbor or property manager who receives the packages, and then drops it inside your home. Pros: Individual firewall ports don't need to be opened, more suited for high scalability needs, can support large volume data integration, easier management of one connection vs a multitude of open ports Cons: VPN setup, specific hardware support, requires cloud provider to support virtual private computing Pattern: Reverse Proxy / API Gateway The on-premise system uses a reverse proxy "API gateway" software on the DMZ to receive messages. The reverse proxy can be implemented using various mechanisms e.g. Oracle API Gateway provides firewall and proxy services along with comprehensive security, auditing, throttling benefits. If a firewall already exists, then Oracle Service Bus or Oracle HTTP Server virtual hosts can provide reverse proxy implementations on the DMZ. Custom built implementations are also possible if specific functionality (such as message store-n-forward) is needed. In the home analogy, this pattern sits in between cutting mail slots and handing over keys. Instead, you install (and maintain) a mailbox in your home premises outside your door. The post office delivers the parcels in your mailbox, from where you can securely retrieve it. Pros: Very secure, very flexible Cons: Introduces a new software component, needs DMZ deployment and management Pattern: On-Premise Agent (Tunneling) A light weight "agent" software sits behind the firewall and initiates the communication with the cloud, thereby avoiding firewall issues. It then maintains a bi-directional connection either with pull or push based approaches using (or abusing, depending on your viewpoint) the HTTP protocol. Programming protocols such as Comet, WebSockets, HTTP CONNECT, HTTP SSH Tunneling etc. are possible implementation options. In the home analogy, a resident receives the parcel from the postal worker by opening the door, however you still take precautions with chain locks and package inspections. Pros: Light weight software, IT doesn't need to setup anything Cons: May bypass critical firewall checks e.g. virus scans, separate software download, proliferation of non-IT managed software Conclusion The patterns above are some of the most commonly encountered ones for cloud to on-premise integration. Selecting the right pattern for your project involves looking at your scalability needs, security restrictions, sync vs asynchronous implementation, near real-time vs batch expectations, cloud provider capabilities, budget, and more. In some cases, the basic "Pull from Cloud" may be acceptable, whereas in others, an extensive VPN topology may be well justified. For more details on the Oracle cloud integration strategy, download this white paper.

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  • On the art of self-promotion

    - by Tony Davis
    I attended Brent Ozar's Building the Fastest SQL Servers session at Tech Ed last week, and found myself engulfed in a 'perfect storm' of excellent technical and presentational skills coupled with an astute awareness of the value of promoting one's work. I spend a lot of time at such events talking to developers and DBAs about the value of blogging and writing articles, and my impression is that some could benefit from a touch less modesty and a little more self-promotion. I sense a reticence in many would-be writers. Is what I have to say important enough? Haven't far more qualified and established commentators, MVPs and so on, already said it? While it's a good idea to pick reasonably fresh and interesting topics, it's more important not to let such fears lead to writer's block. In the eyes of any future employer, your published writing is an extension of your resume. They will not care that a certain MVP knows how to solve problem x, but they will be very interested to see that you have tackled that same problem, and solved it in your own way, and described the process in your own voice. In your current job, your writing is one of the ways you can express to your peers, and to the organization as a whole, the value of what you contribute. Many Developers and DBAs seem to rely on the idea that their work will speak for itself, and that their skill shines out from it. Unfortunately, this isn't always true. Many Development DBAs, for example, will be painfully aware of the massive effort involved in tuning and adding resilience to rapidly developed applications. However, others in the organization who are unaware of what's involved in getting an application that is 'done' ready for production may dismiss such efforts as fussiness or conservatism. At the dark end of the development cycle, chickens come home to roost, but their droppings tend to land on those trying to clear up the mess. My advice is this: next time you fix a bug or improve the resilience or performance of a database or application, make sure that you use team meetings, informal discussions and so on to ensure that people understand what the problem was and what you had to do to fix it. Use your blog to describe, generally, the process you adopted, the resources you used and the insights that came from your work. Encourage your colleagues to do the same. By spreading the art of self-promotion to everyone involved in an IT project, we get a better idea of the extent of the work and the value of the contribution of all the team members. As always, we'd love to hear what you think. This very week, Simple-talk launches its new blogging platform. If any of this has moved you to 'throw your hat into the ring', drop us a mail at [email protected]. Cheers, Tony.

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  • Documentation Changes in Solaris 11.1

    - by alanc
    One of the first places you can see Solaris 11.1 changes are in the docs, which have now been posted in the Solaris 11.1 Library on docs.oracle.com. I spent a good deal of time reviewing documentation for this release, and thought some would be interesting to blog about, but didn't review all the changes (not by a long shot), and am not going to cover all the changes here, so there's plenty left for you to discover on your own. Just comparing the Solaris 11.1 Library list of docs against the Solaris 11 list will show a lot of reorganization and refactoring of the doc set, especially in the system administration guides. Hopefully the new break down will make it easier to get straight to the sections you need when a task is at hand. Packaging System Unfortunately, the excellent in-depth guide for how to build packages for the new Image Packaging System (IPS) in Solaris 11 wasn't done in time to make the initial Solaris 11 doc set. An interim version was published shortly after release, in PDF form on the OTN IPS page. For Solaris 11.1 it was included in the doc set, as Packaging and Delivering Software With the Image Packaging System in Oracle Solaris 11.1, so should be easier to find, and easier to share links to specific pages the HTML version. Beyond just how to build a package, it includes details on how Solaris is packaged, and how package updates work, which may be useful to all system administrators who deal with Solaris 11 upgrades & installations. The Adding and Updating Oracle Solaris 11.1 Software Packages was also extended, including new sections on Relaxing Version Constraints Specified by Incorporations and Locking Packages to a Specified Version that may be of interest to those who want to keep the Solaris 11 versions of certain packages when they upgrade, such as the couple of packages that had functionality removed by an (unusual for an update release) End of Feature process in the 11.1 release. Also added in this release is a document containing the lists of all the packages in each of the major package groups in Solaris 11.1 (solaris-desktop, solaris-large-server, and solaris-small-server). While you can simply get the contents of those groups from the package repository, either via the web interface or the pkg command line, the documentation puts them in handy tables for easier side-by-side comparison, or viewing the lists before you've installed the system to pick which one you want to initially install. X Window System We've not had good X11 coverage in the online Solaris docs in a while, mostly relying on the man pages, and upstream X.Org docs. In this release, we've integrated some X coverage into the Solaris 11.1 Desktop Adminstrator's Guide, including sections on installing fonts for fontconfig or legacy X11 clients, X server configuration, and setting up remote access via X11 or VNC. Of course we continue to work on improving the docs, including a lot of contributions to the upstream docs all OS'es share (more about that another time). Security One of the things Oracle likes to do for its products is to publish security guides for administrators & developers to know how to build systems that meet their security needs. For Solaris, we started this with Solaris 11, providing a guide for sysadmins to find where the security relevant configuration options were documented. The Solaris 11.1 Security Guidelines extend this to cover new security features, such as Address Space Layout Randomization (ASLR) and Read-Only Zones, as well as adding additional guidelines for existing features, such as how to limit the size of tmpfs filesystems, to avoid users driving the system into swap thrashing situations. For developers, the corresponding document is the Developer's Guide to Oracle Solaris 11 Security, which has been the source for years for documentation of security-relevant Solaris API's such as PAM, GSS-API, and the Solaris Cryptographic Framework. For Solaris 11.1, a new appendix was added to start providing Secure Coding Guidelines for Developers, leveraging the CERT Secure Coding Standards and OWASP guidelines to provide the base recommendations for common programming languages and their standard API's. Solaris specific secure programming guidance was added via links to other documentation in the product doc set. In parallel, we updated the Solaris C Libary Functions security considerations list with details of Solaris 11 enhancements such as FD_CLOEXEC flags, additional *at() functions, and new stdio functions such as asprintf() and getline(). A number of code examples throughout the Solaris 11.1 doc set were updated to follow these recommendations, changing unbounded strcpy() calls to strlcpy(), sprintf() to snprintf(), etc. so that developers following our examples start out with safer code. The Writing Device Drivers guide even had the appendix updated to list which of these utility functions, like snprintf() and strlcpy(), are now available via the Kernel DDI. Little Things Of course all the big new features got documented, and some major efforts were put into refactoring and renovation, but there were also a lot of smaller things that got fixed as well in the nearly a year between the Solaris 11 and 11.1 doc releases - again too many to list here, but a random sampling of the ones I know about & found interesting or useful: The Privileges section of the DTrace Guide now gives users a pointer to find out how to set up DTrace privileges for non-global zones and what limitations are in place there. A new section on Recommended iSCSI Configuration Practices was added to the iSCSI configuration section when it moved into the SAN Configuration and Multipathing administration guide. The Managing System Power Services section contains an expanded explanation of the various tunables for power management in Solaris 11.1. The sample dcmd sources in /usr/demo/mdb were updated to include ::help output, so that developers like myself who follow the examples don't forget to include it (until a helpful code reviewer pointed it out while reviewing the mdb module changes for Xorg 1.12). The README file in that directory was updated to show the correct paths for installing both kernel & userspace modules, including the 64-bit variants.

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  • ADF Business Components

    - by Arda Eralp
    ADF Business Components and JDeveloper simplify the development, delivery, and customization of business applications for the Java EE platform. With ADF Business Components, developers aren't required to write the application infrastructure code required by the typical Java EE application to: Connect to the database Retrieve data Lock database records Manage transactions   ADF Business Components addresses these tasks through its library of reusable software components and through the supporting design time facilities in JDeveloper. Most importantly, developers save time using ADF Business Components since the JDeveloper design time makes typical development tasks entirely declarative. In particular, JDeveloper supports declarative development with ADF Business Components to: Author and test business logic in components which automatically integrate with databases Reuse business logic through multiple SQL-based views of data, supporting different application tasks Access and update the views from browser, desktop, mobile, and web service clients Customize application functionality in layers without requiring modification of the delivered application The goal of ADF Business Components is to make the business services developer more productive.   ADF Business Components provides a foundation of Java classes that allow your business-tier application components to leverage the functionality provided in the following areas: Simplifying Data Access Design a data model for client displays, including only necessary data Include master-detail hierarchies of any complexity as part of the data model Implement end-user Query-by-Example data filtering without code Automatically coordinate data model changes with business services layer Automatically validate and save any changes to the database   Enforcing Business Domain Validation and Business Logic Declaratively enforce required fields, primary key uniqueness, data precision-scale, and foreign key references Easily capture and enforce both simple and complex business rules, programmatically or declaratively, with multilevel validation support Navigate relationships between business domain objects and enforce constraints related to compound components   Supporting Sophisticated UIs with Multipage Units of Work Automatically reflect changes made by business service application logic in the user interface Retrieve reference information from related tables, and automatically maintain the information when the user changes foreign-key values Simplify multistep web-based business transactions with automatic web-tier state management Handle images, video, sound, and documents without having to use code Synchronize pending data changes across multiple views of data Consistently apply prompts, tooltips, format masks, and error messages in any application Define custom metadata for any business components to support metadata-driven user interface or application functionality Add dynamic attributes at runtime to simplify per-row state management   Implementing High-Performance Service-Oriented Architecture Support highly functional web service interfaces for business integration without writing code Enforce best-practice interface-based programming style Simplify application security with automatic JAAS integration and audit maintenance "Write once, run anywhere": use the same business service as plain Java class, EJB session bean, or web service   Streamlining Application Customization Extend component functionality after delivery without modifying source code Globally substitute delivered components with extended ones without modifying the application   ADF Business Components implements the business service through the following set of cooperating components: Entity object An entity object represents a row in a database table and simplifies modifying its data by handling all data manipulation language (DML) operations for you. These are basically your 1 to 1 representation of a database table. Each table in the database will have 1 and only 1 EO. The EO contains the mapping between columns and attributes. EO's also contain the business logic and validation. These are you core data services. They are responsible for updating, inserting and deleting records. The Attributes tab displays the actual mapping between attributes and columns, the mapping has following fields: Name : contains the name of the attribute we expose in our data model. Type : defines the data type of the attribute in our application. Column : specifies the column to which we want to map the attribute with Column Type : contains the type of the column in the database   View object A view object represents a SQL query. You use the full power of the familiar SQL language to join, filter, sort, and aggregate data into exactly the shape required by the end-user task. The attributes in the View Objects are actually coming from the Entity Object. In the end the VO will generate a query but you basically build a VO by selecting which EO need to participate in the VO and which attributes of those EO you want to use. That's why you have the Entity Usage column so you can see the relation between VO and EO. In the query tab you can clearly see the query that will be generated for the VO. At this stage we don't need it and just use it for information purpose. In later stages we might use it. Application module An application module is the controller of your data layer. It is responsible for keeping hold of the transaction. It exposes the data model to the view layer. You expose the VO's through the Application Module. This is the abstraction of your data layer which you want to show to the outside word.It defines an updatable data model and top-level procedures and functions (called service methods) related to a logical unit of work related to an end-user task. While the base components handle all the common cases through built-in behavior, customization is always possible and the default behavior provided by the base components can be easily overridden or augmented. When you create EO's, a foreign key will be translated into an association in our model. It defines the type of relation and who is the master and child as well as how the visibility of the association looks like. A similar concept exists to identify relations between view objects. These are called view links. These are almost identical as association except that a view link is based upon attributes defined in the view object. It can also be based upon an association. Here's a short summary: Entity Objects: representations of tables Association: Relations between EO's. Representations of foreign keys View Objects: Logical model View Links: Relationships between view objects Application Model: interface to your application  

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  • Help identify the pattern for reacting on updates

    - by Mike
    There's an entity that gets updated from external sources. Update events are at random intervals. And the entity has to be processed once updated. Multiple updates may be multiplexed. In other words there's a need for the most current state of entity to be processed. There's a point of no-return during processing where the current state (and the state is consistent i.e. no partial update is made) of entity is saved somewhere else and processing goes on independently of any arriving updates. Every consequent set of updates has to trigger processing i.e. system should not forget about updates. And for each entity there should be no more than one running processing (before the point of no-return) i.e. the entity state should not be processed more than once. So what I'm looking for is a pattern to cancel current processing before the point of no return or abandon processing results if an update arrives. The main challenge is to minimize race conditions and maintain integrity. The entity sits mainly in database with some files on disk. And the system is in .NET with web-services and message queues. What comes to my mind is a database queue-like table. An arriving update inserts row in that table and the processing is launched. The processing gathers necessary data before the point of no-return and once it reaches this barrier it looks into the queue table and checks whether there're more recent updates for the entity. If there are new updates the processing simply shuts down and its data is discarded. Otherwise the processing data is persisted and it goes beyond the point of no-return. Though it looks like a solution to me it is not quite elegant and I believe this scenario may be supported by some sort of middleware. If I would use message queues for this then there's a need to access the queue API in the point of no-return to check for the existence of new messages. And this approach also lacks elegance. Is there a name for this pattern and an existing solution?

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  • University teaches DOS-style C++, how to deal with it

    - by gaidal
    Half a year ago I had a look at available programming educations. I chose this one because unlike most of the choices: The majority of the courses seemed to be about something concrete and useful; the languages used are C++ and Java which are platform-independent; later courses include developing for mobile devices and a course on Android development, which seemed modern and relevant. Now after two introductory courses we're just starting with C++, and my programming professor seems a bit weird. He's tested us on things like "why should you use constants" and "why are globals bad" in a kind of mechanical way, without much context, before teaching actual programming. His handouts use system("pause"), system("cls"), and getch() from some conio.h that seems ancient according to what I've read. I just did a task that was about printing the "ASCII letters from 32 to 255" (huh?), with an example picture showing a table with Windows' Extended ASCII - of course I got other results for 128-255 on my Arch Linux that uses Unicode, and this isn't mentioned at all. I don't know, it just doesn't seem right... As if he is teaching programming because he has to, perhaps? Should I bring such things up? Hmm. I was looking forward to learning from someone who really knows stuff, and in an academic, rigorous way, like SICP or something. Aren't professors in programming supposed to be like that? I studied math for a while and every teacher and assistant there were really precise about what they said, but this is my second programming teacher that is sort of disappointing. Oh well. Now, question: Is this what to expect from universities or Not OK, and how do I deal with it? I have never touched the language C++ (or C) until now, and am not the right person to jump up and say "This is So Wrong!", so if I google something and find 10 people who say "xxx is blasphemy", how do I skillfully communicate this? I do think it would be better for those classmates who are total beginners not to learn bad habits (such as these vibes of total ignorance of other platforms!) during the upcoming courses, but don't want to disrespect the teacher. I don't know if it's reasonable or just cocky to bring up things like "what about other platforms?" or "but what about this article or stackoverflow answer that I read that said..." for every assignment? Or, if he keeps ignoring non-Windows-programming, should I give up and focus on my own projects or somehow argue that this really isn't OK nowadays? Are there any programming teachers out there, what do you think? By the way these are web-based courses, all interaction between teachers and students takes place in a forum. EDIT: A few answers seem to be making some incorrect assumptions, so maybe I should add a few things. I have been doing programming for fun on and off for 10 years, am pretty comfortable in 3 languages and read programming blogs et c regularly. Also, I feel kind of done being a student, having a degree in another field. I just need another, relevant diploma to work as a programmer, so I'm going back for that. Studying computer science for 5 years is not for me anymore, even though I enjoy learning and solving problems in my free time. Second, let me highlight that I don't expect it to be like the industry at all, quite the contrary. I expect it to be academic, dry and unnecessarily correct. No, it's not just math. Every professor I have had in math, or Japanese (major) or Chinese (minor) have been very very academic, discussing subtle points for hours with passion. But the courses I'm taking now and a previous one in programming don't seem serious. They neither resemble industry NOR academia. That is the problem. And it's not because I can't learn programming anyway. Third, I don't necessarily want to learn C++ or Android development, and I know I could teach myself those and anything else if I wanted to. But I am going back to school anyway, and those platform-independent languages and mobile stuff made me think that maybe they're serious about teaching something relevant here. Seems like I got this wrong, but we'll see.

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  • C++ and SDL resource management for 2D game

    - by KuruptedMagi
    My first question is about stateManagers. I do not use the singleton pattern (read many random posts with various reasons not to use it), I have gameStateManager which runs the pointer cCurrentGameState-render(), etc. I want to make a transitioning game, this engine should ideally cover both a platformer and a bird's eye RPG (with some recoding, I just mean the base engine), both of which will load different levels and events, such as world map, dungeon, shops, etc. So I then thought, rather then having to store all this data within all the states, I would break the engine into gameStates, and playStates... when gameState reaches gameStatePlay(), gameStatePlay simply runs the usual handleInput, logic, and render for the playStates, just as the low level gameStateManager does. This lets me store all the player data within the base playstate class without storing useless data in the gameStates. Now I have added a seperate mapEditor, which uses editorStates from gameStateEditor. Is this too much usage of the gameState concept? It seems to work pretty well for me, so I was wondering if I am too far off a common implementation of this. My second question is on image resources. I have my sprite class with nothing but static members, mainly loadImage, applySurface, and my screen pointer. I also have a map pairing imageName enums with actual SDL_Surface pointers, and one pairing clipNumber enums with a wrapper class for a vector of clips, so that each reference in the map can have different amounts of clips with different sizes. I thought it would be better to store all these images, and screen within one static body, since 20 different goblins all use the same sprite sheet, and all need to print to the same screen, and of course, this way I do not need to pass my screen reference to every little entity. The imageMap seems to work very well, I can even add the ability to search through the map at creation of entity type to see if a particular image at creation, creating if it doesnt exist, and destroying the image if the last entity that needs it was just destroyed. The vectored clip map however, seems to take too long to initialize, so if i run past the state that initializes them to fast, the game crashes <. Plus, the clip map call is half of this line =P SPRITE::applySurface( cEditorMap.cTiles[x][y].iX, cEditorMap.cTiles[x][y].iY, SPRITE::mImages[ IMAGE_TILEMAP ], SPRITE::screen, SPRITE::mImageClips[IMAGE_TILEMAP]->clips.at( cEditorMap.cTiles[x][y].iTileType ) ); Again, do I have the right idea? I like the imageMap, but am I better off with each entity storing its own clips? My last question is about collision detection. I only grasp the basics, will look at per-pixel and circular soon, but how can I determine which side the collision comes from with just the basic square collision detection, I tried breaking each entity into 4 collision zones, but that just gave me problems with walking through walls and the like <. Also, is per-pixel color collision a good way to decide what collision just occured, or is checking multiple colors for multiple entities too taxing each cycle?

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  • Many sources of movement in an entity system

    - by Sticky
    I'm fairly new to the idea of entity systems, having read a bunch of stuff (most usefully, this great blog and this answer). Though I'm having a little trouble understanding how something as simple as being able to manipualate the position of an object by an undefined number of sources. That is, I have my entity, which has a position component. I then have some event in the game which tells this entity to move a given distance, in a given time. These events can happen at any time, and will have different values for position and time. The result is that they'd be compounded together. In a traditional OO solution, I'd have some sort of MoveBy class, that contains the distance/time, and an array of those inside my game object class. Each frame, I'd iterate through all the MoveBy, and apply it to the position. If a MoveBy has reached its finish time, remove it from the array. With the entity system, I'm a little confused as how I should replicate this sort of behavior. If there were just one of these at a time, instead of being able to compound them together, it'd be fairly straightforward (I believe) and look something like this: PositionComponent containing x, y MoveByComponent containing x, y, time Entity which has both a PositionComponent and a MoveByComponent MoveBySystem that looks for an entity with both these components, and adds the value of MoveByComponent to the PositionComponent. When the time is reached, it removes the component from that entity. I'm a bit confused as to how I'd do the same thing with many move by's. My initial thoughts are that I would have: PositionComponent, MoveByComponent the same as above MoveByCollectionComponent which contains an array of MoveByComponents MoveByCollectionSystem that looks for an entity with a PositionComponent and a MoveByCollectionComponent, iterating through the MoveByComponents inside it, applying/removing as necessary. I guess this is a more general problem, of having many of the same component, and wanting a corresponding system to act on each one. My entities contain their components inside a hash of component type - component, so strictly have only 1 component of a particular type per entity. Is this the right way to be looking at this? Should an entity only ever have one component of a given type at all times?

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  • JavaOne 2012: Camel, Twitter, Coherence, Wicket and GlassFish

    - by Bruno.Borges
    Before joining Oracle as Product Manager for WebLogic and GlassFish for Latin America, at the beggining of this year I proposed two talks to JavaOne USA that I had been presenting in Brazil for quite a while. One of them I presented last year at ApacheCon in Vancouver, Canada as well in JavaOne Brazil. In June I got the news that they were accepted as Alternate Sessions. Surprisingly enough, few weeks later and at the same time I joined Oracle, I received the news that they were officially accepted and put on schedule. Tomorrow I'll be flying to San Francisco, to my first JavaOne in the United States, and I wanted to share with you what I'm going to present there. My two sessions are these ones: Wed, 10/03, 4:30pm - CON2989 Leverage Enterprise Integration Patterns with Apache Camel and TwitterOn this one, you will be introducted to the Apache Camel framework that I had been talking about in Brazil at conferences, before joining Oracle, and to a component I contributed to integrate with Twitter. Also, you will have a preview of a new component I've been working on to integrate Camel with the Oracle Coherence distributed cache. Thu, 10/04, 3:30pm - CON3395 How Scala, Wicket, and Java EE Can Improve Web DevelopmentThis one I've been working on for quite a while. It was based on an idea to have an architecture that could be as agile as frameworks and technologies such as Ruby on Rails, PHP or Python, for rapid web development. You will be introduced to the Apache Wicket framework, another Apache project I enjoy working with and gave lots of talks at Brazilian conferences, including JavaOne Brazil, JustJava, QCon SP, and The Developers Conference. You will also be introduced to the Scala language and how to create nice DSLs to boost productiveness. And last but not least, the Java EE 6 platform, that offers an awesome improvement from previous versions with its CDI, JPA, EJB3 and JAX-RS features for web development. Other events I will be participating during my stay in SF: Geeks Bike Ride GlassFish Community Event GlassFish and Friends Party    If you have any other event to suggest, please do suggest! It's my first JavaOne and I'm really looking forward to enjoying everything. See you guys in a few days!!

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  • Modelling highly specific business requirements

    - by AndyBursh
    How can one go about modelling highly specific business requirements, which have no precedent in the system? Take for example the following requirement: When a purchase order contains N lines, is over X value in total and is being recorded against project Y, an email needs to be sent to persons A and B with the details This requirement supplements other requirements surrounding purchase orders, but comes in at a much later date in response to some ongoing problem elsewhere in the business. Persons A and B are not part of any role or group in the system, and don't hold any specific responsibility; they are simply the two people the business has appointed to receive these emails in this very specific case. Projects are also data driven, so project Y has no special properties to distinguish it from any other project. The only way to identify it is to compare its identifier to a magic number. How can one go about modelling this kind of case without introducing too much additional complexity? That I can think of right now, there are a couple of options. Perform the checks and actions inline with the existing code. Here we find the correct spot in the code, check the conditions in the requirement and send the emails to hardcoded addresses. Of course this is fraught with issues. At the very least it stops working if one of these people leaves or changes their email address. At worst you have to ensure that any tests and test data are aware that additional actions are taken for a specific set of criteria. Introduce some form of events system. Here we introduce an eventing system, so that we might react to some event, and fulfil the requirement outside of the usual path of execution. This sounds like a cleaner solution than option 1, but the work involved is ultimately probably slightly overkill for this one small requirement. That said, having it in place does allow the system to handle these kinds of specific requirements consistently and easily in the future. Are there any other (good/better) ways of handling highly specific requirements? I mean other than telling the other parts of the business no!

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  • UK OUG Conference Highlights and Insights

    - by Richard Bingham
    As per my preemptive post, this was the first time the annual conference organized by the UK Oracle User Group (UKOUG) was split into two events, one for Oracle Applications and another in December for Oracle Technology. Apps13, as it was branded, was hailed as a success, with over 1000 registered attendees and three days of sessions, exhibition, round-tables and many other types of content. As this poster on their stand illustrates, the UKOUG is a strong community with popular participants from both big and small Oracle partners and customers. The venue was a more intimate setting than previous years also, allowing everyone to casually bump into those they hoped to. It gave a real feeling of an Apps Community. The main themes over the days where CRM and Customer Experience, HCM, and FIN/SCM. This allowed people to attend just one focused day if they wanted. In addition the Apps Transformation stream ran across all three days, offering insights, advice, and details on the newer product solutions like Fusion Applications.  Here are some of the key take-aways I got from the conference, specific to my role in Fusion Applications Developer Relations: User Experience continues to be a significant reason for adopting some of the newer application products available, with immediately obvious gains in user productivity and satisfaction reported by customers. Also this doesn't stop with the baked-in UX either, with their Design Patterns proving popular and indeed currently being extended to including things like extending on ADF mobile and customizing the Simplified UI. More on this to come from us soon. The executive sessions emphasized the "it's a journey" phrase, illustrating that modern business applications are powered by technologies such as Cloud, Mobile, Social and Big Data and these can be harnessed to help propel your organization forward. Indeed the emphasis is away from the traditional vendor prescribed linear applications road map, and towards plotting a course based on business priorities supported by a broad range of integrated solutions. To help with this several conference sessions demoed the new "Applications Navigator" tool, developed in partnership with OUG members, which offers a visual framework to help organizations plan their Oracle Applications investments around business and technology imperatives. Initial reaction was positive, especially as customers do not need to decipher Oracle's huge product catalog and embeds the best blend of proven and integrated applications solutions. We'll share more on this when it is generally available. Several sessions focused around explanations and interpretation of Oracle OpenWorld 2013, helping highlight the key Oracle Applications messages and directions. With a relative small percentage of conference attendees also at OpenWorld (from a show of hands) this was a popular way to distill the information available down into specific items of interest for the community. Please note the original OpenWorld 2013 content is still available for download but will not remain available forever (via the Oracle website OpenWorld Content Catalog > pick a session > see the PDF download). With the release of E-Business Suite 12.2 the move to develop and deploy on the Fusion Middleware stack becomes a reality for many Oracle Applications customers. This coupled with recent E-Business Suite features such as the Integrated SOA Gateway and the E-Business Suite SDK for Java, illustrates how the gap between the technologies and techniques involved in extending E-Business Suite and Fusion Applications is quickly narrowing. We'll see this merging continue to evolve going forwards. Getting started with Oracle Cloud Applications is actually easier than many customers expected, with a broad selection of both large and medium sized organizations explaining how they added new features to their existing Oracle Applications portfolios. New functionality available from Fusion HCM and CX are popular extensions that do not have to disrupt those core business services. Coexistence is the buzzword here, and the available integration is also simpler than many expected, commonly involving an initial setup data load, then regularly incremental synchronizations, often without a need for real-time constant communication between systems. With much of this pre-built already the implementation process is also quite rapid. With most people dressed in suits, we wanted to get the conversations going without the traditional english reserve, so we decided to make ourselves a bit more obvious, as the photo below shows. This seemed to be quite successful and helped those interested identify and approach us. Keep a look out for similar again. In fact if you're in the UK there is an "Apps Transformation Day" planned by the UKOUG for the 19th March 2014, with more details to follow. Again something we'll be sure to participate in. I am hoping to attend the next half of the UKOUG annual conference, Tech13, that focuses more on Oracle technology and where there is more likely to be larger attendance of those interested in the lower-level aspects of applications customization and development. If you're going, let me know and maybe we can meet up.

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  • Mounting ddrescue image after recovery (in over my head)

    - by BorgDomination
    I'm having problems mounting the recovery image. I've tried to mount the image multiple ways. quark@DS9 ~ $ sudo mount -t ext4 /media/jump1/1recover/sdb1.img /mnt mount: wrong fs type, bad option, bad superblock on /dev/loop0, missing codepage or helper program, or other error In some cases useful info is found in syslog - try dmesg | tail or so quark@DS9 ~ $ sudo mount -r -o loop /media/jump1/1recover/sdb1.img recover mount: you must specify the filesystem type quark@DS9 ~ $ sudo mount /media/jump1/1recover/sdb1.img mnt mount: you must specify the filesystem type It doesn't even give me detailed information on the file I just made, nautilus says it's 160gb. quark@DS9 ~ $ file /media/jump1/1recover/sdb1.img /media/jump1/1recover/sdb1.img: data quark@DS9 ~ $ mmls /media/jump1/1recover/sdb1.img Cannot determine partition type I'm not sure what I'm doing wrong or if I started this process incorrectly from the beginning. I've outlined what I've done so far below. I'm clueless, I'd appreciate if someone had some input for me. What I have done from the beginning My laptop has two hard drives. One has the dual boot Win7 / Linux Mint system files. Secondary one contained my /home folder. The laptop was jarred and the /home disk was broken. I tried a LiveCD recovery, it failed. Wouldn't even load a Live session with the disk installed. So I turned to ddrescue. quark@DS9 ~ $ sudo fdisk -l Disk /dev/sda: 160.0 GB, 160041885696 bytes 255 heads, 63 sectors/track, 19457 cylinders, total 312581808 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x0009fc18 Device Boot Start End Blocks Id System /dev/sda1 * 2048 112642047 56320000 7 HPFS/NTFS/exFAT /dev/sda2 138033152 312580095 87273472 83 Linux /dev/sda3 112644094 138033151 12694529 5 Extended /dev/sda5 112644096 132173823 9764864 83 Linux /dev/sda6 132175872 138033151 2928640 82 Linux swap / Solaris Partition table entries are not in disk order Disk /dev/sdb: 160.0 GB, 160041885696 bytes 255 heads, 63 sectors/track, 19457 cylinders, total 312581808 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x0002a8ea Device Boot Start End Blocks Id System /dev/sdb1 * 63 312576704 156288321 83 Linux Disk /dev/sdc: 1000.2 GB, 1000204886016 bytes 255 heads, 63 sectors/track, 121601 cylinders, total 1953525168 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0xed6d054b Device Boot Start End Blocks Id System /dev/sdc1 63 1953520064 976760001 7 HPFS/NTFS/exFAT sda - 160g internal, holds all system files and all computer functions. sdb - 160g internal, BROKEN, contains about 140g of data I'd like to recover. sdc - 1T external, contains recovery image. Only place that has space to do all this. From this site, https://apps.education.ucsb.edu/wiki/Ddrescue I used this script to create an image of the broken hard drive. I changed the destination to the external USB drive. #!/bin/sh prt=sdb1 src=/dev/$prt dst=/media/jump1/1recover/$prt.img log=$dst.log sudo time ddrescue --no-split $src $dst $log sudo time ddrescue --direct --max-retries=3 $src $dst $log sudo time ddrescue --direct --retrim --max-retries=3 $src $dst $log Everything looked like it came off without a hitch: quark@DS9 ~ $ sudo bash recover1 Press Ctrl-C to interrupt Initial status (read from logfile) rescued: 0 B, errsize: 0 B, errors: 0 Current status rescued: 160039 MB, errsize: 4096 B, current rate: 35588 B/s ipos: 3584 B, errors: 1, average rate: 22859 kB/s opos: 3584 B, time from last successful read: 0 s Finished 12.78user 1060.42system 1:56:41elapsed 15%CPU (0avgtext+0avgdata 4944maxresident)k 312580958inputs+0outputs (1major+601minor)pagefaults 0swaps Press Ctrl-C to interrupt Initial status (read from logfile) rescued: 160039 MB, errsize: 4096 B, errors: 1 Current status rescued: 160039 MB, errsize: 1024 B, current rate: 0 B/s ipos: 1536 B, errors: 1, average rate: 13 B/s opos: 1536 B, time from last successful read: 1.3 m Finished 0.00user 0.00system 3:43.95elapsed 0%CPU (0avgtext+0avgdata 4944maxresident)k 238inputs+0outputs (3major+374minor)pagefaults 0swaps Press Ctrl-C to interrupt Initial status (read from logfile) rescued: 160039 MB, errsize: 1024 B, errors: 1 Current status rescued: 160039 MB, errsize: 1024 B, current rate: 0 B/s ipos: 1536 B, errors: 1, average rate: 0 B/s opos: 1536 B, time from last successful read: 3.7 m Finished 0.00user 0.00system 3:43.56elapsed 0%CPU (0avgtext+0avgdata 4944maxresident)k 8inputs+0outputs (0major+376minor)pagefaults 0swaps It looks like, from where I'm standing it worked perfectly. Here's the log: # Rescue Logfile. Created by GNU ddrescue version 1.14 # Command line: ddrescue --direct --retrim --max-retries=3 /dev/sdb1 /media/jump1/1recover/sdb1.img /media/jump1/1recover/sdb1.img.log # current_pos current_status 0x00000600 + # pos size status 0x00000000 0x00000400 + 0x00000400 0x00000400 - 0x00000800 0x254314FC00 + I'm not sure how to proceed. Does this mean all of my data is lost???????? Appreciate ANY input!

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  • Brain Teaser: How Did I Do This (Part 1: The Solution)

    - by Geertjan
    In Part 1: The Challenge, published this time last week, I introduced a "brain teaser". The brain teaser asks you to figure out how to allow images and other files to be meaningfully dropped onto a NetBeans Platform application, i.e., on the drop something useful should happen with the dropped file: if the file is an image, the image should open in the IDE; if the file is a PDF document, the PDF viewer should open externally; if the file is a text file, it should open as a text in the IDE, etc. Solution. And here is the solution: http://bits.netbeans.org/dev/javadoc/org-openide-windows/org/openide/windows/ExternalDropHandler.html When an implementation of the "ExternalDropHandler" class is available in the global Lookup, and an object is being dragged over some part of the main window, the window system may call the methods of this class to decide whether it can accept or reject the drag operation. And when the object is actually dropped, this class will be asked to handle the drop. OK, so go ahead and implement the above class and put it into the Lookup. Or... guess what? The NetBeans Platform has a default implementation of the above class, appropriately named "DefaultExternalDropHandler". Not only is this useful to learn about how to implement the ExternalDropHandler class (i.e., by reading the source here): you can simply include the module that contains this class in your own NetBeans Platform application and then your application will be able to receive external drag/drop events and do something meaningful with them thanks to the DefaultExternalDropHandler. Do this: Open your NetBeans Platform application in NetBeans IDE. Right-click the application in the Projects window and choose Properties. In the Libraries tab, expand the "ide" cluster, and select "User Utilities". (That's where "DefaultExternalDropHandler.java" is found and registered in the Lookup.) Now click the "Resolve" button, if it appears, because some additional related modules need to now be included, if they haven't been included yet. Again in the "ide" cluster in the Libraries tab, select "Image". That's the Image Editor. Click OK. Run the application. Drag an image or some other type of file into your application, from outside the application, and you'll see the application tries to handle the drop. If the file being dragged is an image, it will open in the Image Editor, which you included in the previous step of these instructions. Hurray, you're done. Without any programming at all, you've added a cool new feature to your application.

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  • Navigation in a #WP7 application with MVVM Light

    - by Laurent Bugnion
    In MVVM applications, it can be a bit of a challenge to send instructions to the view (for example a page) from a viewmodel. Thankfully, we have good tools at our disposal to help with that. In his excellent series “MVVM Light Toolkit soup to nuts”, Jesse Liberty proposes one approach using the MVVM Light messaging infrastructure. While this works fine, I would like to show here another approach using what I call a “view service”, i.e. an abstracted service that is invoked from the viewmodel, and implemented on the view. Multiple kinds of view services In fact, I use view services quite often, and even started standardizing them for the Windows Phone 7 applications I work on. If there is interest, I will be happy to show other such view services, for example Animation services, responsible to start/stop animations on the view. Dialog service, in charge of displaying messages to the user and gathering feedback. Navigation service, in charge of navigating to a given page directly from the viewmodel. In this article, I will concentrate on the navigation service. The INavigationService interface In most WP7 apps, the navigation service is used in quite a straightforward way. We want to: Navigate to a given URI. Go back. Be notified when a navigation is taking place, and be able to cancel. The INavigationService interface is quite simple indeed: public interface INavigationService { event NavigatingCancelEventHandler Navigating; void NavigateTo(Uri pageUri); void GoBack(); } Obviously, this interface can be extended if necessary, but in most of the apps I worked on, I found that this covers my needs. The NavigationService class It is possible to nicely pack the navigation service into its own class. To do this, we need to remember that all the PhoneApplicationPage instances use the same instance of the navigation service, exposed through their NavigationService property. In fact, in a WP7 application, it is the main frame (RootFrame, of type PhoneApplicationFrame) that is responsible for this task. So, our implementation of the NavigationService class can leverage this. First the class will grab the PhoneApplicationFrame and store a reference to it. Also, it registers a handler for the Navigating event, and forwards the event to the listening viewmodels (if any). Then, the NavigateTo and the GoBack methods are implemented. They are quite simple, because they are in fact just a gateway to the PhoneApplicationFrame. The whole class is as follows: public class NavigationService : INavigationService { private PhoneApplicationFrame _mainFrame; public event NavigatingCancelEventHandler Navigating; public void NavigateTo(Uri pageUri) { if (EnsureMainFrame()) { _mainFrame.Navigate(pageUri); } } public void GoBack() { if (EnsureMainFrame() && _mainFrame.CanGoBack) { _mainFrame.GoBack(); } } private bool EnsureMainFrame() { if (_mainFrame != null) { return true; } _mainFrame = Application.Current.RootVisual as PhoneApplicationFrame; if (_mainFrame != null) { // Could be null if the app runs inside a design tool _mainFrame.Navigating += (s, e) => { if (Navigating != null) { Navigating(s, e); } }; return true; } return false; } } Exposing URIs I find that it is a good practice to expose each page’s URI as a constant. In MVVM Light applications, a good place to do that is the ViewModelLocator, which already acts like a central point of setup for the views and their viewmodels. Note that in some cases, it is necessary to expose the URL as a string, for instance when a query string needs to be passed to the view. So for example we could have: public static readonly Uri MainPageUri = new Uri("/MainPage.xaml", UriKind.Relative); public const string AnotherPageUrl = "/AnotherPage.xaml?param1={0}&param2={1}"; Creating and using the NavigationService Normally, we only need one instance of the NavigationService class. In cases where you use an IOC container, it is easy to simply register a singleton instance. For example, I am using a modified version of a super simple IOC container, and so I can register the navigation service as follows: SimpleIoc.Register<INavigationService, NavigationService>(); Then, it can be resolved where needed with: SimpleIoc.Resolve<INavigationService>(); Or (more frequently), I simply declare a parameter on the viewmodel constructor of type INavigationService and let the IOC container do its magic and inject the instance of the NavigationService when the viewmodel is created. On supported platforms (for example Silverlight 4), it is also possible to use MEF. Or, of course, we can simply instantiate the NavigationService in the ViewModelLocator, and pass this instance as a parameter of the viewmodels’ constructor, injected as a property, etc… Once the instance has been passed to the viewmodel, it can be used, for example with: NavigationService.NavigateTo(ViewModelLocator.ComparisonPageUri); Testing Thanks to the INavigationService interface, navigation can be mocked and tested when the viewmodel is put under unit test. Simply implement and inject a mock class, and assert that the methods are called as they should by the viewmodel. Conclusion As usual, there are multiple ways to code a solution answering your needs. I find that view services are a really neat way to delegate view-specific responsibilities such as animation, dialogs and of course navigation to other classes through an abstracted interface. In some cases, such as the NavigationService class exposed here, it is even possible to standardize the implementation and pack it in a class library for reuse. I hope that this sample is useful! Happy coding. Laurent   Laurent Bugnion (GalaSoft) Subscribe | Twitter | Facebook | Flickr | LinkedIn

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  • Delay command execution over sockets

    - by David
    I've been trying to fix the game loop in a real time (tick delay) MUD. I realized using Thread.Sleep would seem clunky when the user spammed commands through their choice of client (Zmud, etc) e.g. east;south;southwest would wait three move ticks and then output everything from the past couple rooms. The game loop basically calls a Flush and Fill method for each socket during each tick (50ms) private void DoLoop() { Stopwatch stopWatch = new Stopwatch(); stopWatch.Start(); while (running) { // for each socket, flush and fill ConnectionMonitor.Update(); stopWatch.Stop(); WaitIfNeeded(stopWatch.ElapsedMilliseconds); stopWatch.Reset(); } } The Fill method fires the command events, but as mentioned before, they currently block using Thread.Sleep. I tried adding a "ready" flag to the state object that attempts to execute the command along with a queue of spammed commands, but it ends up executing one command and queuing up the rest i.e. each subsequent command executes something that got queued up that should've been executed before. I must be missing something about the timer. private readonly Queue<SpammedCommand> queuedCommands = new Queue<SpammedCommand>(); private bool ready = true; private void TryExecuteCommand(string input) { var commandContext = CommandContext.Create(input); var player = Server.Current.Database.Get<Player>(Session.Player.Key); var commandInfo = Server.Current.CommandLookup .FindCommand(commandContext.CommandName, player.IsAdmin); if (commandInfo != null) { if (!ready) { // queue command queuedCommands.Enqueue(new SpammedCommand() { Context = commandContext, Info = commandInfo }); return; } if (queuedCommands.Count > 0) { // queue the incoming command queuedCommands.Enqueue(new SpammedCommand() { Context = commandContext, Info = commandInfo, }); // dequeue and execute var command = queuedCommands.Dequeue(); command.Info.Command.Execute(Session, command.Context); setTimeout(command.Info.TickLength); return; } commandInfo.Command.Execute(Session, commandContext); setTimeout(commandInfo.TickLength); } else { Session.WriteLine("Command not recognized"); } } Finally, setTimeout was supposed to set the execution delay (TickLength) for that command, and makeReady just sets the ready flag on the state object to true. private void setTimeout(TickDelay tickDelay) { ready = false; var t = new System.Timers.Timer() { Interval = (long) tickDelay, AutoReset = false, }; t.Elapsed += makeReady; t.Start(); // fire this in tickDelay ms } // MAKE READYYYYY!!!! private void makeReady(object sender, System.Timers.ElapsedEventArgs e) { ready = true; } Am I missing something about the System.Timers.Timer created in setTimeout? How can I execute (and output) spammed commands per TickLength without using Thread.Sleep?

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  • SMTP POP3 & PST. Acronyms from Hades.

    - by mikef
    A busy SysAdmin will occasionally have reason to curse SMTP. It is, certainly, one of the strangest events in the history of IT that such a deeply flawed system, designed originally purely for campus use, should have reached its current dominant position. The explanation was that it was the first open-standard email system, so SMTP/POP3 became the internet standard. We are, in consequence, dogged with a system with security weaknesses so extreme that messages are sent in plain text and you have no real assurance as to who the message came from anyway (SMTP-AUTH hasn't really caught on). Even without the security issues, the use of SMTP in an office environment provides a management nightmare to all commercial users responsible for complying with all regulations that control the conduct of business: such as tracking, retaining, and recording company documents. SMTP mail developed from various Unix-based systems designed for campus use that took the mail analogy so literally that mail messages were actually delivered to the users, using a 'store and forward' mechanism. This meant that, from the start, the end user had to store, manage and delete messages. This is a problem that has passed through all the releases of MS Outlook: It has to be able to manage mail locally in the dreaded PST file. As a stand-alone system, Outlook is flawed by its neglect of any means of automatic backup. Previous Outlook PST files actually blew up without warning when they reached the 2 Gig limit and became corrupted and inaccessible, leading to a thriving industry of 3rd party tools to clear up the mess. Microsoft Exchange is, of course, a server-based system. Emails are less likely to be lost in such a system if it is properly run. However, there is nothing to stop users from using local PSTs as well. There is the additional temptation to load emails into mobile devices, or USB keys for off-line working. The result is that the System Administrator is faced by a complex hybrid system where backups have to be taken from Servers, and PCs scattered around the network, where duplication of emails causes storage issues, and document retention policies become impossible to manage. If one adds to that the complexity of mobile phone email readers and mail synchronization, the problem is daunting. It is hardly surprising that the mood darkens when SysAdmins meet and discuss PST Hell. If you were promoted to the task of tormenting the souls of the damned in Hades, what aspects of the management of Outlook would you find most useful for your task? I'd love to hear from you. Cheers, Michael

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  • Android - Force Close - Null Pointer on Canvas?

    - by user22241
    Please bear with me. I have a very odd problem. Basically, my app so far, has 3 activities (a main splash screen, an 'options/menu' screen and the main app). If I follow the very specific steps oulined below, I get a 'null pointer exception' in the 2nd activity) and the app force closes...... Here are the steps: Start the app (a game based on Surfaceview), tap through to the third activity so the game is running, then hit the home key so the game is paused and put to the background, the activity/app is ended through DDMS in the SDK then restarted on the device (all OK so far), now if I hit the back key on the device twice in quick succession, it happens. All other sequence of events is fine, even to the point of pressing the back key, waiting for the previous activity to show, then hitting back again - all OK. Only when the back key is pressed twice in quick succession following all the above steps does the problem occur. I'm assuming that the canvas isn't ready as it's showing as 'null' when this happens, but I'm not sure why this is happening as surely it's happening when I'm trying to go back to activity 1, but the logcat shows the error in activity 2. if I stop the activity running my 'doDraw' method (which referenced the canvas), then all is OK - so I can safely assume it is the canvas causing the problem. Also, if I skip my first activity (which is a very basic full-screen button which just displays a splashscreen and waits for the user to tap the screen), and make my 2nd activity the launch activity, again, it is OK. this is the part of the code that I think is probably relevant: @Override public void surfaceChanged(SurfaceHolder arg0, int arg1, int arg2, int arg3) { vheight = this.getHeight(); vwidth = this.getWidth(); } @Override public void surfaceCreated(SurfaceHolder holder) { vheight = this.getHeight(); vwidth = this.getWidth(); this.viewWidth = vwidth; this.viewHeight = vheight; if (runthread==false){ if (preThread.getState()==Thread.State.TERMINATED){ preThread = new OptionsThread(thisholder, thiscontext, thishandler); } preThread.setRunning(true); preThread.start();} } @Override public void surfaceDestroyed(SurfaceHolder holder) { preThread.setRunning(false); //Stop the loop boolean retry = true; //Stop the thread while (retry) { try { preThread.join(); retry = false; } catch (InterruptedException e) { } } Thank you all for any help you can offer

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  • Creating a Yes/No MessageBox in a NuGet install/uninstall script

    - by ParadigmShift
    Sometimes getting a little feedback during the install/uninstall process of a NuGet package could be really useful. Instead of accounting for all possible ways to install your NuGet package for every user, you can simplify the installation by clarifying with the user what they want. This example shows how to generate a windows yes/no message box to get input from the user in the PowerShell install or uninstall script. We’ll use the prompt on the uninstall to confirm if the user wants to delete a custom setting that the initial install placed in their configuration.  Obviously you could use the prompt in any way you want. The objects of the message box are generated similar to the controls in the code behind of a WinForm. At the beginning of your script enter this: param($installPath, $toolsPath, $package, $project)   # Set up path variables $solutionDir = Get-SolutionDir $projectName = (Get-Project).ProjectName $projectPath = Join-Path $solutionDir $projectName   ################################################################################################ # WinForm generation for prompt ################################################################################################ function Ask-Delete-Custom-Settings { [void][reflection.assembly]::loadwithpartialname("System.Windows.Forms") [Void][reflection.assembly]::loadwithpartialname("System.Drawing")   $title = "Package Uninstall" $message = "Delete the customized settings?" #Create form and controls $form1 = New-Object System.Windows.Forms.Form $label1 = New-Object System.Windows.Forms.Label $btnYes = New-Object System.Windows.Forms.Button $btnNo = New-Object System.Windows.Forms.Button   #Set properties of controls and form ############ # label1 # ############ $label1.Location = New-Object System.Drawing.Point(12,9) $label1.Name = "label1" $label1.Size = New-Object System.Drawing.Size(254,17) $label1.TabIndex = 0 $label1.Text = $message   ############# # btnYes # ############# $btnYes.Location = New-Object System.Drawing.Point(156,45) $btnYes.Name = "btnYes" $btnYes.Size = New-Object System.Drawing.Size(48,25) $btnYes.TabIndex = 1 $btnYes.Text = "Yes"   ########### # btnNo # ########### $btnNo.Location = New-Object System.Drawing.Point(210,45) $btnNo.Name = "btnNo" $btnNo.Size = New-Object System.Drawing.Size(48,25) $btnNo.TabIndex = 2 $btnNo.Text = "No"   ########### # form1 # ########### $form1.ClientSize = New-Object System.Drawing.Size(281,86) $form1.Controls.Add($label1) $form1.Controls.Add($btnYes) $form1.Controls.Add($btnNo) $form1.Name = "Form1" $form1.Text = $title #Event Handler $btnYes.add_Click({btnYes_Click}) $btnNo.add_Click({btnNo_Click}) return $form1.ShowDialog() } function btnYes_Click { #6 = Yes $form1.DialogResult = 6 } function btnNo_Click { #7 = No $form1.DialogResult = 7 } ################################################################################################ This has also wired up the click events to the form.  This is all it takes to create the message box. Now we have to actually use the message box and get the user’s response or this is all pointless.  We’ll then delete the section of the application/web configuration called <Custom.Settings> [xml] $configXmlContent = Get-Content $configFile   Write-Host "Please respond to the question in the Dialog Box." $dialogResult = Ask-Delete-Custom-Settings #6 = Yes #7 = No Write-Host "dialogResult = $dialogResult" if ($dialogResult.ToString() -eq "Yes") { Write-Host "Deleting customized settings" $customSettingsNode = $configXmlContent.configuration.Item("Custom.Settings") $configXmlContent.configuration.RemoveChild($customSettingsNode) $configXmlContent.Save($configFile) } if ($dialogResult.ToString() -eq "No") { Write-Host "Do not delete customized settings" } The part where I check if ($dialog.Result.ToString() –eq “Yes”) could just as easily check the value for either 6 or 7 (Yes or No).  I just personally decided I liked this way better.   Shahzad Qureshi is a Software Engineer and Consultant in Salt Lake City, Utah, USA His certifications include: Microsoft Certified System Engineer 3CX Certified Partner Global Information Assurance Certification – Secure Software Programmer – .NET He is the owner of Utah VoIP Store at http://www.utahvoipstore.com/ and SWS Development at http://www.swsdev.com/ and publishes windows apps under the name Blue Voice.

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  • AS3 - At exactly 23 empty alpha channels, images below stop drawing

    - by user46851
    I noticed, while trying to draw large numbers of circles, that occasionally, there would be some kind of visual bug where some circles wouldn't draw properly. Well, I narrowed it down, and have noticed that if there is 23 or more objects with 00 for an alpha value on the same spot, then the objects below don't draw. It appears to be on a pixel-by-pixel basis, since parts of the image still draw. Originally, this problem was noticed with a class that inherited Sprite. It was confirmed to also be a problem with Sprites, and now Bitmaps, too. If anyone can find a lower-level class than Bitmap which doesn't have this problem, please speak up so we can try to find the origin of the problem. I prepared a small test class that demonstrates what I mean. You can change the integer value at line 20 in order to see the three tests I came up with to clearly show the problem. Is there any kind of workaround, or is this just a limit that I have to work with? Has anyone experienced this before? Is it possible I'm doing something wrong, despite the bare-bones implementation? package { import flash.display.Sprite; import flash.events.Event; import flash.display.Bitmap; import flash.display.BitmapData; public class Main extends Sprite { public function Main():void { if (stage) init(); else addEventListener(Event.ADDED_TO_STAGE, init); } private function init(e:Event = null):void { removeEventListener(Event.ADDED_TO_STAGE, init); // entry point Test(3); } private function Test(testInt:int):void { if(testInt==1){ addChild(new Bitmap(new BitmapData(200, 200, true, 0xFFFF0000))); for (var i:int = 0; i < 22; i++) { addChild(new Bitmap(new BitmapData(100, 100, true, 0x00000000))); } } if(testInt==2){ addChild(new Bitmap(new BitmapData(200, 200, true, 0xFFFF0000))); for (var j:int = 0; j < 23; j++) { addChild(new Bitmap(new BitmapData(100, 100, true, 0x00000000))); } } if(testInt==3){ addChild(new Bitmap(new BitmapData(200, 200, true, 0xFFFF0000))); for (var k:int = 0; k < 22; k++) { addChild(new Bitmap(new BitmapData(100, 100, true, 0x00000000))); } var M:Bitmap = new Bitmap(new BitmapData(100, 100, true, 0x00000000)); M.x += 50; M.y += 50; addChild(M); } } } }

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  • Spotlight on an office - Nairobi, Kenya

    - by Maria Sandu
    Hi everyone, my name is Joash Mitei. I am a graduate Intern at Oracle Systems Kenya and I will briefly take you through our offices and the working environment here in Nairobi, Kenya. I’ve been with Oracle since February 2012 and I’m responsible for Applications Pre-sales focusing on Oracle EPM and E-Business Suite. My background is Finance and Accounting therefore joining Oracle was almost a totally a different ball game but the transition has been smooth. The Oracle offices here are located on the second floor of Mebank Towers. We moved to the 2nd floor just three months ago from the 5th floor mainly because of the growing workforce. We are covering the whole Eastern Africa region hence diversity in culture is evident. This is a plus since you get to interact with people of very different backgrounds, cultures and ways of thinking. The building itself is on the outskirts of the CBD hence free from the hustle and bustle of the town. The office is split into different sections; there is a main working area which has an open desk design that fosters interaction between colleagues, there are 4 conference rooms for meetings and presentations, there are 3 quiet rooms for a little privacy when needed and there is a dining area for meals and ‘hanging out’. The working environment is world-class, to say the least. The employees are very professional, quite smart and needless to say, very busy. There are 4 interns covering sales and pre-sales in both Tech and Apps. As an intern you get support from your supervisor but you are required to show initiative yourself and thus the need to be very pro-active and inquisitive. The local management is well structured and communicative to ensure effectiveness and efficiency in the office. Apart from the daily work, we usually have events to boost staff morale such as ‘TGIF hang -out’, football matches against each other or versus other companies, and team building retreats. All these are monumental in fostering the RED POTENTIAL. We also do numerous CSR activities in the local communities . Well, that’s the Kenyan office for you. Glad to be your tour guide. Have a superb day!

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  • How do I keep user input and rendering independent of the implementation environment?

    - by alex
    I'm writing a Tetris clone in JavaScript. I have a fair amount of experience in programming in general, but am rather new to game development. I want to separate the core game code from the code that would tie it to one environment, such as the browser. My quick thoughts led me to having the rendering and input functions external to my main game object. I could pass the current game state to the rendering method, which could render using canvas, elements, text, etc. I could also map input to certain game input events, such as move piece left, rotate piece clockwise, etc. I am having trouble designing how this should be implemented in my object. Should I pass references to functions that the main object will use to render and process user input? For example... var TetrisClone = function(renderer, inputUpdate) { this.renderer = renderer || function() {}; this.inputUpdate = input || function() {}; this.state = {}; }; TetrisClone.prototype = { update: function() { // Get user input via function passed to constructor. var inputEvents = this.inputUpdate(); // Update game state. // Render the current game state via function passed to constructor. this.renderer(this.state); } }; var renderer = function(state) { // Render blocks to browser page. } var inputEvents = {}; var charCodesToEvents = { 37: "move-piece-left" /* ... */ }; document.addEventListener("keypress", function(event) { inputEvents[event.which] = true; }); var inputUpdate = function() { var translatedEvents = [], event, translatedEvent; for (event in inputEvents) { if (inputEvents.hasOwnProperty(event)) { translatedEvent = charCodesToEvents[event]; translatedEvents.push(translatedEvent); } } inputEvents = {}; return translatedEvents; } var game = new TetrisClone(renderer, inputUpdate); Is this a good game design? How would you modify this to suit best practice in regard to making a game as platform/input independent as possible?

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  • Spotlight on an office - Moscow

    - by Maria Sandu
    Probably the most famous place in Moscow, after Red Square, is the centre of Moscow. Here you can find beautiful buildings that seem to touch the sky, located on the banks of the river. In one of these high towers you can find the Oracle offices, friendly and modern. The stunning view will keep capture your attention for a couple of minutes and then you can enjoy a delicious coffee and take a seat at your desk, starting a new day. My name is Dmitry and I can tell you that we’re enjoying every minute spent in the office and that’s because of the pleasant atmosphere. As soon as you enter the offices, the friendly environment will make you feel more relaxed. Even though the space is split between the different departments, we interact and communicate a lot. We take our cup of coffee or tea together and discuss our achievements and all sort of subjects in the kitchen or in the open space. One of my favorite parts are the festive events when we celebrate with cakes and goodies. Any birthday or new arrival is a good reason for a tea party! We have some work-related traditions that help us as employees. One of them is the monthly Tech Hour when Experts from the Pre-sales team discuss technical topics and about the most recent innovations within the company. Lunch is another good opportunity to interact and chat. We have a variety of options, such as the two kitchens or the vast number of restaurants where you can serve up anything you want. As we are right in the centre of Moscow, you can choose between Sushi, Italian Pasta and all sorts of food. We usually go with our colleagues to have lunch. If you care about your health, I have very good news for you as nearby there are two first-class fitness centres with swimming pools, yoga and various sport classes that you can attend. My suggestion would be to either start or end your day with a visit to the swimming pool for a well-deserved hour of relaxation. As I mentioned before, we’re right in the heart of Moscow, so after work you can spend some time in the large shopping centers where you can choose between many different entertainment options. We often go to bowling or to the cinema. I hope I have given you a glimpse into working life at the Oracle offices in Moscow, a really great and pleasant place to work in, so follow us on http://campus.oracle.com for our latest vacancies and internships.

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  • Introduction to Agile Development

    - by Grant Fritchey
    Even though my current job is a little weird, I still consider myself to be a DBA. I didn’t start that way in IT. I came through support and into development. I loved development. There was a constant struggle to attempt to improve your code, your understanding, and, most importantly, the process of development itself. Development can be slow and tedious. Left alone, developers can simply disappear to build a project and not come back for two years, at which time they deliver it. But, maybe that software isn’t what you wanted, or it’s no longer needed, or who knows what. So developers are constantly attempting to improve their processes in order to deliver more relavent software quicker (something DBAs could learn about). I really admire it. One of the many processes that has come out of that constant striving is known as Agile. As the name implies, Agile development attempts to come up with a quick, fast turning, business aware, well, for want of a word, agile, process that is more responsive to the needs of the business. There are tons and tons of books and blogs and videos on the subject that can get you going. But, Agile isn’t easy (note, Easy is not part of the name). Agile processes can be hard. I’ve worked on multiple agile teams, some successful, some not. The two principal differences between the teams were their discipline and their knowledge of the process. Discipline, that comes from within. But knowledge, ah, well there I can help. Red Gate is bringing a series of free instructional events to the United States in a few weeks time focused primarily on SQL Server (click here right now to register while there’s still space). We’re also offering some .NET instruction too. That’s a full day, free, with top experts in the business. But, the next day, there’s a full day session introducing Agile. You can go to this and learn how to do Agile. Develop that knowledge that will enable you to successfully use the Agile process. Go to this web site to check it out. No, this event is not free, but not everything can be. And it’s not just for developers. DBAs, you need to learn this stuff too. Management could also benefit from understanding these processes (because you guys can help to enforce discipline). It’s really for everyone involved in the development process.

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