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• WiFi connected to router, but no internet connection

  - by Quetzacotl

  I just got a new notebook, a ThinkPad Edge E530, and installed Ubuntu on it. I'm pretty new to Ubuntu. On the same laptop, running Windows 7, the Wi-Fi connection works fine. Ethernet connection works both on Win7 and on Ubuntu. Only Wi-Fi on Ubuntu does not work; it connects to the Wi-Fi access point but I don't have Internet access. My wireless card is Intel Centrino Wireless-N 2230. What can fix the problem? EDIT: ifconfig -a eth0 Link encap:Ethernet HWaddr b8:88:e3:30:72:34 UP BROADCAST MULTICAST MTU:1500 Metric:1 RX packets:0 errors:0 dropped:0 overruns:0 frame:0 TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:0 (0.0 B) TX bytes:0 (0.0 B) Interrupt:43 Base address:0x8000 lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 inet6 addr: ::1/128 Scope:Host UP LOOPBACK RUNNING MTU:16436 Metric:1 RX packets:163 errors:0 dropped:0 overruns:0 frame:0 TX packets:163 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:10124 (10.1 KB) TX bytes:10124 (10.1 KB) usb0 Link encap:Ethernet HWaddr 02:15:e0:ec:01:00 UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:0 errors:0 dropped:0 overruns:0 frame:0 TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:0 (0.0 B) TX bytes:0 (0.0 B) wlan0 Link encap:Ethernet HWaddr 68:5d:43:43:71:e1 inet addr:192.168.2.101 Bcast:192.168.2.255 Mask:255.255.255.0 inet6 addr: fe80::6a5d:43ff:fe43:71e1/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:40 errors:0 dropped:0 overruns:0 frame:0 TX packets:220 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:2801 (2.8 KB) TX bytes:26230 (26.2 KB) route -n Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface 0.0.0.0 192.168.2.1 0.0.0.0 UG 0 0 0 wlan0 169.254.0.0 0.0.0.0 255.255.0.0 U 1000 0 0 wlan0 192.168.2.0 0.0.0.0 255.255.255.0 U 2 0 0 wlan0 cat /etc/resolv.conf # Dynamic resolv.conf(5) file for glibc resolver(3) generated by resolvconf(8) # DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTEN nameserver 127.0.0.1 iwconfig lo no wireless extensions. usb0 no wireless extensions. wlan0 IEEE 802.11bgn ESSID:"SATELITE" Mode:Managed Frequency:2.462 GHz Access Point: 00:1F:1F:8D:CC:08 Bit Rate=1 Mb/s Tx-Power=16 dBm Retry long limit:7 RTS thr:off Fragment thr:off Power Management:off Link Quality=60/70 Signal level=-50 dBm Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0 Tx excessive retries:93 Invalid misc:243 Missed beacon:0 eth0 no wireless extensions.

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• Windows8, JavaScript and HTML5 - A good thing?

  - by Albers

  Most of us have seen the Windows 8 news regarding support for native HTML5/JavaScript applications. The press has pushed this as a potential threat to the .NET developer community because JavaScript and HTML5 were called "our new developer platform". The press release refers to "Web-connected and Web-powered apps built using HTML5 and JavaScript that have access to the full power of the PC.".Microsoft has also been hush on details related to these comments. Before we buy the hype and start worrying about a world where we drop our Visual Studio licenses and buy DreamWeaver - let's think about how Windows 8 HTML/JavaScript applications would be implemented. The HTML5 spec offers support for offline applications, but this won't offer the OS-integrated experience the press release refers to. MS has to be planning a way to extend access beyond the traditional JavaScript feature set. Microsoft has a similar option today: HTML Applications or HTAs. They come close to required features, but HTAs need ActiveX or Java integration to provide the promised OS-level access. I'm guessing that Microsoft's future OS strategy isn't built on developers cranking out ActiveX controls or Java applets. So where is Microsoft headed? One possibility is that MS builds a new JavaScript framework from the ground up outside their current APIs. Another idea would be for Microsoft to add support for JavaScript as a first class .NET language using the Dynamic Language Runtime. A solution based on the DLR could be integrated into an HTA-like model to provide the promised access, along with the full range of features in .NET Framework. Security comes included in the Framework. And the work necessary to support this integration would tie in nicely with the effort MS has recently made providing better JavaScript and HTML5 support in Visual Studio 2010. As a bonus, a full-fledged JavaScript DLR implementation would allow single language web solutions across client and server (think node.js) and would appeal to developers who are familiar with JavaScript but have less experience with the Microsoft tech stack. We will all get a better picture after the Build conference in September. But in the mean time we know that Microsoft has a reputation for providing strong developer support. We might want to reserve our harshest judgement and consider that the press release could hint at new opportunities for .NET development.

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• Pretty URL in ADF Faces of JDeveloper 11.1.2.2

  - by Frank Nimphius

  Many features planned for Oracle JDeveloper 12c find their way into current releases of Oracle JDeveloper 11g R1 and JDeveloper 11g R2. One example of such a feature is "pretty URL" - or "clean URL" as the Oracle JDeveloper 11g R2 (11.1.2.2) documentation puts it. "A.2.3.24 Clean URLs Historically, ADF Faces has used URL parameters to hold information, such as window IDs and state. However, URL parameters can prevent search engines from recognizing when URLs are actually the same, and therefore interfere with analytics. URL parameters can also interfere with bookmarking. By default, ADF Faces removes URL parameters using the HTML5 History Management API. If that API is unavailable, then session cookies are used.You can also manually configure how URL parameters are removed using the context parameter oracle.adf.view.rich.prettyURL.OPTIONS. Set the parameter to off so that no parameters are removed. Set the parameter to useHistoryApi to only use the HTML5 History Management API. If a browser does not support this API, then no parameters will be removed. Set the parameter to useCookies to use session cookies to remove parameters. If the browser does not support cookies, then no parameters will be removed." See: http://docs.oracle.com/cd/E26098_01/web.1112/e16181/ap_config.htm#ADFUI12856 So basically, what this part in the documentation says is: In JDeveloper 11g R2 (11.1.2.2), Oracle ADF Faces automatically removes its internally used dynamic parameters from the URL You can influence the setting with the prettyURL.OPTIONS context option, which however is not recommended you to do because the default behavior is able to detect if the browser client supports HTML 5 History management or not. In the latter case it the uses a session cookie and if this doesn't work, falls back to the "old" URL parameter adding. The information that is not so explicit and clearly mentioned in the documentation is that this is only for ADF Faces parameters (such as _afrLoop, Adf-Window-Id, etc.), but not the ADF controller token (_adf.ctrl-state)! Removing the ADF controller token is an enhancement request that will be implemented in Oracle JDeveloper 12c

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• What are the drawbacks of sending XML to browsers and let them apply XSLT?

  - by MainMa

  Context Working as a freelance developer, I often made websites completely based on XSLT. In other words, on every request, an XML file is generated, containing everything we need to know about the page content: the name of the user currently logged in, the top menu entries, if this menu is dynamic/configurable, the text to display in a specific area of the page, etc. Then XSL process (caches, etc.) it to HTML/XHTML page to send to the browser. It has a good point to make it easier to create small-scale websites, especially with PHP. It is a sort of template engine, but which I prefer to other template engines because it's much more powerful than most of template engines, and because I know it better and like it. It is also possible, when need, to give an access to raw XML data on demand for an automated access, without the need to create separate APIs. Of course, it will fail completely on any medium-scale or large-scale website, since, even with good caching techniques, XSL still degrades overall website performance and requires more CPU serverside. Question Modern browsers have the ability to take an XML file and to transform it with an associated XSL file declared in XML like <?xml-stylesheet href="demo.xslt" type="text/xsl"?>. Firefox 3 can do it. Internet Explorer 8 can do it too. It means that it is possible to migrate XSL processing from the server to the client side for 50% of users (according on browser statistics on several websites where I may want to implement this). It means that those 50% of users will receive only the XML file at each request, thus reducing their and server's bandwidth (XML file being much shorter than its processed HTML analog), and reducing server's CPU usage. What are the drawbacks of this technique? I thought about several ones, but it doesn't apply in this situation: Difficult implementation and the need to choose, based on the browser request, when to send raw XML and when to transform it to HTML instead. Obviously, the system will not be much more difficult then the actual one. The only change to make is to add XSL file link to every XML, and to add a browser check. More IO and bandwidth usage, since the XSLT file will be downloaded by the browsers, instead of being cached by the server. I don't think it will be a problem, since XSLT file will be cached by the browsers (like images, or CSS, or JavaScript files are cached actually). Possibly some problems on client side, like maybe problems when saving a page in some browsers. Difficulty to debug code: it is impossible to obtain an HTML source the browser is actually using, since the only displayed source is the downloaded XML. On the other hand, I rarely go look at HTML code on client side, and in most cases, it is unusable directly (whitespace being removed).

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• WebCenter Customer Spotlight: Guizhou Power Grid Company

  - by me

  Author: Peter Reiser - Social Business Evangelist, Oracle WebCenter  Solution SummaryGuizhou Power Grid Company is responsible for power grid planning, construction, management, and power distribution in Guizhou Province, serving 39 million people. Giuzhou has 49,823 employees and an annual revenue of over $5 Billion. The business objectives were to consolidate information contained in disparate systems into a single knowledge repository and provide a safe and efficient way for staff and managers to access, query, share, manage, and store business information. Guizhou Power Grid Company saved more than US$693,000 in storage costs, reduced  average search times from 180 seconds to 5 seconds and solved 80% to 90% of technology and maintenance issues by searching the Oracle WebCenter Content management system. Company OverviewA wholly owned subsidiary of China Southern Power Grid Company Limited, Guizhou Power Grid Company is responsible for power grid planning, construction, management, and power distribution in Guizhou Province, serving 39 million people. Giuzhou has 49,823 employees and an annual revenue of over $5 Billion. Business ChallengesThe business objectives were to consolidate information contained in disparate systems, such as the customer relationship management and power grid management systems, into a single knowledge repository and provide a safe and efficient way for staff and managers to access, query, share, manage, and store business information. Solution DeployedGuizhou Power Grid Company  implemented Oracle WebCenter Content to build a content management system that enabled the secure, integrated management and storage of information, such as documents, records, images, Web content, and digital assets. The content management solution was integrated with the power grid, customer service, maintenance, and other business systems, as well as the corporate Web site. Business Results Saved more than US$693,000 in storage costs and shortened the material distribution time by integrating the knowledge management solution with the power grid, customer service, maintenance, and other business systems, as well as the corporate Web site Enabled staff to search 31,650 documents using catalogs, multidimensional attributes, and knowledge maps, reducing average search times from 180 seconds to 5 seconds and saving approximately 1,539 hours in annual search time Gained comprehensive document management, format transformation, security, and auditing capabilities Enabled users to upload new documents and supervisors to check the accuracy of these documents online, resulting in improved information quality control Solved 80% to 90% of technology and maintenance issues by searching the Oracle content management system for information, ensuring IT staff can respond quickly to users’ technical problems Improved security by using role-based access controls to restrict access to confidential documents and information Supported the efficient classification of corporate knowledge by using Oracle’s metadata functions to collect, tag, and archive documents, images, Web content, and digital assets “We chose Oracle WebCenter Content, as it is an outstanding integrated content management platform. It has allowed us to establish a system to access, query, share, manage, and store our corporate assets. This has laid a solid foundation for Guizhou Power Grid Company to improve management practices.” Luo Sixi, Senior Information Consultant, Guizhou Power Grid Company Additional Information Guizhou Power Grid Company Customer Snapshot Oracle WebCenter Content

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• Finding a new programming language for web development?

  - by Xeoncross

  I'm wondering if there are any un-biased resources that give good, specific overviews of programming languages and their intended goals. I would like to learn a new language, but visiting the sites of each language isn't working. Each one talks about how great it is without much mention of it's weaknesses or specific goals. Ruby is a dynamic, open source programming language with a focus on simplicity and productivity. Python is a programming language that lets you work more quickly and integrate your systems more effectively. Having been a PHP developer for years, Vic Cherubini sums up my plight well: I knew PHP well, had my own framework, and could work quickly to get something up and running. I programmed like this throughout the MVC revolution. I got better and better jobs (read: better paying, better title) as a PHP developer, but all along the way realizing that the code I wrote on my own time was great, and the code I worked with at work was horrible. Like, worse than horrible. Atrocious. OS Commerce level bad. Having side projects kept me sane, because the code I worked with at work made me miserable. This is why I'm retiring from PHP for my side projects and new programming ventures. I'm spent with PHP. Exhausted, if you will. I've reached a level where I think I'm at the top with it as a language and if I don't move on to a new language soon, I'll be done completely with programming and I do not want that. Languages I've looked at include JavaScript (for node.js), Ruby, Python, & Erlang. I've even thought about Scala or C++. The problem is figuring out which ones are built to handle my needs the best. So where can I go to skip the hype and get real information about the maturity of a platform, the size of the community, and the strengths & weaknesses of that language. If I know these then picking a language to continue my web development should be easy.

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• JS closures - Passing a function to a child, how should the shared object be accessed

  - by slicedtoad

  I have a design and am wondering what the appropriate way to access variables is. I'll demonstrate with this example since I can't seem to describe it better than the title. Term is an object representing a bunch of time data (a repeating duration of time defined by a bunch of attributes) Term has some print functionality but does not implement the print functions itself, rather they are passed in as anonymous functions by the parent. This would be similar to how shaders can be passed to a renderer rather than defined by the renderer. A container (let's call it Box) has a Schedule object that can understand and use Term objects. Box creates Term objects and passes them to Schedule as required. Box also defines the print functions stored in Term. A print function usually takes an argument and uses it to return a string based on that argument and Term's internal data. Sometime the print function could also use data stored in Schedule, though. I'm calling this data shared. So, the question is, what is the best way to access this shared data. I have a lot of options since JS has closures and I'm not familiar enough to know if I should be using them or avoiding them in this case. Options: Create a local "reference" (term used lightly) to the shared data (data is not a primitive) when defining the print function by accessing the shared data through Schedule from Box. Example: var schedule = function(){ var sched = Schedule(); var t1 = Term( function(x){ // Term.print() return (x + sched.data).format(); }); }; Bind it to Term explicitly. (Pass it in Term's constructor or something). Or bind it in Sched after Box passes it. And then access it as an attribute of Term. Pass it in at the same time x is passed to the print function, (from sched). This is the most familiar way for my but it doesn't feel right given JS's closure ability. Do something weird like bind some context and arguments to print. I'm hoping the correct answer isn't purely subjective. If it is, then I guess the answer is just "do whatever works". But I feel like there are some significant differences between the approaches that could have a large impact when stretched beyond my small example.

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• Wrapping REST based Web Service

  - by PaulPerry

  I am designing a system that will be running online under Microsoft Windows Azure. One component is a REST based web service which will really be a wrapper (using proxy pattern) which calls the REST web services of a business partner, which has to do with BLOB storage (note: we are not using azure storage). The majority of the functionality will be taking a request, calling our partner web service, receiving the request and then passing that back to the client. There are a number of reasons for doing this, but one of the big ones is that we are going to support three clients: our desktop application (win and mac), mobile apps (iOS), and a web front end. Having a single API which we then send to our partner protects us if that partner ever changes. I want our service to support both JSON and XML for the data transfer format, JSON for web and probably XML for the desktop and mobile (we already have an XML parser in those products). Our partner also supports both of these formats. I was planning on using ASP.NET MVC 4 with the Web API. As I design this, the thing that concerns me is the static type checking of C#. What if the partner adds or removes elements from the data? We can probably defensively code for that, but I still feel some concern. Also, we have to do a fair amount of tedious coding, to setup our API and then to turn around and call our partner’s API. There probably is not much choice on it though. But, in the back of my mind I wonder if maybe a more dynamic language would be a better choice. I want to reach out and see if anybody has had to do this before, what technology solutions they have used to (I am not attached to this one, these days Azure can host other technologies), and if anybody who has done something like this can point out any issues that came up. Thanks! Researching the issue seems to only find solutions which focus on connecting a SOAP web service over a proxy server, and not what I am referring to here. Note: Cross posted (by suggestion) from http://stackoverflow.com/questions/11906802/wrapping-rest-based-web-service Thank you!

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• Representing complex object dependencies

  - by max

  I have several classes with a reasonably complex (but acyclic) dependency graph. All the dependencies are of the form: class X instance contains an attribute of class Y. All such attributes are set during initialization and never changed again. Each class' constructor has just a couple parameters, and each object knows the proper parameters to pass to the constructors of the objects it contains. class Outer is at the top of the dependency hierarchy, i.e., no class depends on it. Currently, the UI layer only creates an Outer instance; the parameters for Outer constructor are derived from the user input. Of course, Outer in the process of initialization, creates the objects it needs, which in turn create the objects they need, and so on. The new development is that the a user who knows the dependency graph may want to reach deep into it, and set the values of some of the arguments passed to constructors of the inner classes (essentially overriding the values used currently). How should I change the design to support this? I could keep the current approach where all the inner classes are created by the classes that need them. In this case, the information about "user overrides" would need to be passed to Outer class' constructor in some complex user_overrides structure. Perhaps user_overrides could be the full logical representation of the dependency graph, with the overrides attached to the appropriate edges. Outer class would pass user_overrides to every object it creates, and they would do the same. Each object, before initializing lower level objects, will find its location in that graph and check if the user requested an override to any of the constructor arguments. Alternatively, I could rewrite all the objects' constructors to take as parameters the full objects they require. Thus, the creation of all the inner objects would be moved outside the whole hierarchy, into a new controller layer that lies between Outer and UI layer. The controller layer would essentially traverse the dependency graph from the bottom, creating all the objects as it goes. The controller layer would have to ask the higher-level objects for parameter values for the lower-level objects whenever the relevant parameter isn't provided by the user. Neither approach looks terribly simple. Is there any other approach? Has this problem come up enough in the past to have a pattern that I can read about? I'm using Python, but I don't think it matters much at the design level.

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• What's the best way to create a static utility class in python? Is using metaclasses code smell?

  - by rsimp

  Ok so I need to create a bunch of utility classes in python. Normally I would just use a simple module for this but I need to be able to inherit in order to share common code between them. The common code needs to reference the state of the module using it so simple imports wouldn't work well. I don't like singletons, and classes that use the classmethod decorator do not have proper support for python properties. One pattern I see used a lot is creating an internal python class prefixed with an underscore and creating a single instance which is then explicitly imported or set as the module itself. This is also used by fabric to create a common environment object (fabric.api.env). I've realized another way to accomplish this would be with metaclasses. For example: #util.py class MetaFooBase(type): @property def file_path(cls): raise NotImplementedError def inherited_method(cls): print cls.file_path #foo.py from util import * import env class MetaFoo(MetaFooBase): @property def file_path(cls): return env.base_path + "relative/path" def another_class_method(cls): pass class Foo(object): __metaclass__ = MetaFoo #client.py from foo import Foo file_path = Foo.file_path I like this approach better than the first pattern for a few reasons: First, instantiating Foo would be meaningless as it has no attributes or methods, which insures this class acts like a true single interface utility, unlike the first pattern which relies on the underscore convention to dissuade client code from creating more instances of the internal class. Second, sub-classing MetaFoo in a different module wouldn't be as awkward because I wouldn't be importing a class with an underscore which is inherently going against its private naming convention. Third, this seems to be the closest approximation to a static class that exists in python, as all the meta code applies only to the class and not to its instances. This is shown by the common convention of using cls instead of self in the class methods. As well, the base class inherits from type instead of object which would prevent users from trying to use it as a base for other non-static classes. It's implementation as a static class is also apparent when using it by the naming convention Foo, as opposed to foo, which denotes a static class method is being used. As much as I think this is a good fit, I feel that others might feel its not pythonic because its not a sanctioned use for metaclasses which should be avoided 99% of the time. I also find most python devs tend to shy away from metaclasses which might affect code reuse/maintainability. Is this code considered code smell in the python community? I ask because I'm creating a pypi package, and would like to do everything I can to increase adoption.

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• Creating smooth lighting transitions using tiles in HTML5/JavaScript game

  - by user12098

  I am trying to implement a lighting effect in an HTML5/JavaScript game using tile replacement. What I have now is kind of working, but the transitions do not look smooth/natural enough as the light source moves around. Here's where I am now: Right now I have a background map that has a light/shadow spectrum PNG tilesheet applied to it - going from darkest tile to completely transparent. By default the darkest tile is drawn across the entire level on launch, covering all other layers etc. I am using my predetermined tile sizes (40 x 40px) to calculate the position of each tile and store its x and y coordinates in an array. I am then spawning a transparent 40 x 40px "grid block" entity at each position in the array The engine I'm using (ImpactJS) then allows me to calculate the distance from my light source entity to every instance of this grid block entity. I can then replace the tile underneath each of those grid block tiles with a tile of the appropriate transparency. Currently I'm doing the calculation like this in each instance of the grid block entity that is spawned on the map: var dist = this.distanceTo( ig.game.player ); var percentage = 100 * dist / 960; if (percentage < 2) { // Spawns tile 64 of the shadow spectrum tilesheet at the specified position ig.game.backgroundMaps[2].setTile( this.pos.x, this.pos.y, 64 ); } else if (percentage < 4) { ig.game.backgroundMaps[2].setTile( this.pos.x, this.pos.y, 63 ); } else if (percentage < 6) { ig.game.backgroundMaps[2].setTile( this.pos.x, this.pos.y, 62 ); } // etc... (sorry about the weird spacing, I still haven't gotten the hang of pasting code in here properly) The problem is that like I said, this type of calculation does not make the light source look very natural. Tile switching looks too sharp whereas ideally they would fade in and out smoothly using the spectrum tilesheet (I copied the tilesheet from another game that manages to do this, so I know it's not a problem with the tile shades. I'm just not sure how the other game is doing it). I'm thinking that perhaps my method of using percentages to switch out tiles could be replaced with a better/more dynamic proximity forumla of some sort that would allow for smoother transitions? Might anyone have any ideas for what I can do to improve the visuals here, or a better way of calculating proximity with the information I'm collecting about each tile? (PS: I'm reposting this from Stack Overflow at someone's suggestion, sorry about the duplicate!)

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• Hadoop, NOSQL, and the Relational Model

  - by Phil Factor

  (Guest Editorial for the IT Pro/SysAdmin Newsletter)Whereas Relational Databases fit the world of commerce like a glove, it is useless to pretend that they are a perfect fit for all human endeavours. Although, with SQL Server, we’ve made great strides with indexing text, in processing spatial data and processing markup, there is still a problem in dealing efficiently with large volumes of ephemeral semi-structured data. Key-value stores such as Cassandra, Project Voldemort, and Riak are of great value for ephemeral data, and seem of equal value as a data-feed that provides aggregations to an RDBMS. However, the Document databases such as MongoDB and CouchDB are ideal for semi-structured data for which no fixed schema exists; analytics and logging are obvious examples. NoSQL products, such as MongoDB, tackle the semi-structured data problem with panache. MongoDB is designed with a simple document-oriented data model that scales horizontally across multiple servers. It doesn’t impose a schema, and relies on the application to enforce the data structure. This is another take on the old ‘EAV’ problem (where you don’t know in advance all the attributes of a particular entity) It uses a clever replica set design that allows automatic failover, and uses journaling for data durability. It allows indexing and ad-hoc querying. However, for SQL Server users, the obvious choice for handling semi-structured data is Apache Hadoop. There will soon be an ODBC Driver for Apache Hive .and an Add-in for Excel. Additionally, there are now two Hadoop-based connectors for SQL Server; the Apache Hadoop connector for SQL Server 2008 R2, and the SQL Server Parallel Data Warehouse (PDW) connector. We can connect to Hadoop process the semi-structured data and then store it in SQL Server. For one steeped in the culture of Relational SQL Databases, I might be expected to throw up my hands in the air in a gesture of contempt for a technology that was, judging by the overblown journalism on the subject, about to make my own profession as archaic as the Saggar makers bottom knocker (a potter’s assistant who helped the saggar maker to make the bottom of the saggar by placing clay in a metal hoop and bashing it). However, on the contrary, I find that I'm delighted with the advances made by the NoSQL databases in the past few years. Having the flow of ideas from the NoSQL providers will knock any trace of complacency out of the providers of Relational Databases and inspire them into back-fitting some features, such as horizontal scaling, with sharding and automatic failover into SQL-based RDBMSs. It will do the breed a power of good to benefit from all this lateral thinking.

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• How granular should a command be in a CQ[R]S model?

  - by Aaronaught

  I'm considering a project to migrate part of our WCF-based SOA over to a service bus model (probably nServiceBus) and using some basic pub-sub to achieve Command-Query Separation. I'm not new to SOA, or even to service bus models, but I confess that until recently my concept of "separation" was limited to run-of-the-mill database mirroring and replication. Still, I'm attracted to the idea because it seems to provide all the benefits of an eventually-consistent system while sidestepping many of the obvious drawbacks (most notably the lack of proper transactional support). I've read a lot on the subject from Udi Dahan who is basically the guru on ESB architectures (at least in the Microsoft world), but one thing he says really puzzles me: As we get larger entities with more fields on them, we also get more actors working with those same entities, and the higher the likelihood that something will touch some attribute of them at any given time, increasing the number of concurrency conflicts. [...] A core element of CQRS is rethinking the design of the user interface to enable us to capture our users’ intent such that making a customer preferred is a different unit of work for the user than indicating that the customer has moved or that they’ve gotten married. Using an Excel-like UI for data changes doesn’t capture intent, as we saw above. -- Udi Dahan, Clarified CQRS From the perspective described in the quotation, it's hard to argue with that logic. But it seems to go against the grain with respect to SOAs. An SOA (and really services in general) are supposed to deal with coarse-grained messages so as to minimize network chatter - among many other benefits. I realize that network chatter is less of an issue when you've got highly-distributed systems with good message queuing and none of the baggage of RPC, but it doesn't seem wise to dismiss the issue entirely. Udi almost seems to be saying that every attribute change (i.e. field update) ought to be its own command, which is hard to imagine in the context of one user potentially updating hundreds or thousands of combined entities and attributes as it often is with a traditional web service. One batch update in SQL Server may take a fraction of a second given a good highly-parameterized query, table-valued parameter or bulk insert to a staging table; processing all of these updates one at a time is slow, slow, slow, and OLTP database hardware is the most expensive of all to scale up/out. Is there some way to reconcile these competing concerns? Am I thinking about it the wrong way? Does this problem have a well-known solution in the CQS/ESB world? If not, then how does one decide what the "right level" of granularity in a Command should be? Is there some "standard" one can use as a starting point - sort of like 3NF in databases - and only deviate when careful profiling suggests a potentially significant performance benefit? Or is this possibly one of those things that, despite several strong opinions being expressed by various experts, is really just a matter of opinion?

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• Are there any concerns with using a static read-only unit of work so that it behaves like a cache?

  - by Rowan Freeman

  Related question: How do I cache data that rarely changes? I'm making an ASP.NET MVC4 application. On every request the security details about the user will need to be checked with the area/controller/action that they are accessing to see if they are allowed to view it. The security information is stored in the database. For example: User Permission UserPermission Action ActionPermission A "Permission" is a token that is applied to an MVC action to indicate that the token is required in order to access the action. Once a user is given the permission (via the UserPermission table) then they have the token and can therefore access the action. I've been looking in to how to cache this data (since it rarely changes) so that I'm only querying in-memory data and not hitting a database (which is a considerable performance hit at the moment). I've tried storing things in lists, using a caching provider but I either run in to problems or performance doesn't improve. One problem that I constantly run in to is that I'm using lazy loading and dynamic proxies with EntityFramework. This means that even if I ToList() everything and store them somewhere static, the relationships are never populated. For example, User.Permissions is an ICollection but it's always null. I don't want to Include() everything because I'm trying to keep things simple and generic (and easy to modify). One thing I know is that an EntityFramework DbContext is a unit of work that acts with 1st-level caching. That is, for the duration of the unit of work, everything that is accessed is cached in memory. I want to create a read-only DbContext that will exist indefinitely and will only be used to read about permission data. Upon testing this it worked perfectly; my page load times went from 200ms+ to 20ms. I can easily force the data to refresh at certain intervals or simply leave it to refresh when the application pool is recycled. Basically it will behave like a cache. Note that the rest of the application will interact with other contexts that exist per request as normal. Is there any disadvantage to this approach? Could I be doing something different?

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• Another Custom Property Locator: a Library of Books

  - by Cindy McMullen

  Introduction The previous post gave an introduction to custom property locators and showed how create one using JDeveloper.  This post continues on the custom locator theme, with a slightly more complex locator: a library of books.  It demonstrates using the DAO pattern to delegate data access from the Locator, which is likely how many actual backing stores will integrate with the Locator.  You can imagine, rather than a library of books, the data store might be a user database of sorts.  The same sort of pattern would apply. This post uses the BookLocator example originally shown in the WebCenter documentation, but has: updated the source code to reflect the final Property APIs includes the steps for generating the namespace and property definition files via JDeveloper detailed usage of the PropertyService APIs Getting Started If you're new to JDeveloper, you might want to check out this tutorial.  There is also the "Jump-Start to using Personalization" blog post that you might find useful.  Otherwise, if you're already familiar with both, you can skip those tutorials and jump right in to using JDeveloper. Download the BookLocator.zip file (which has been updated from the original post) and unzip it to a new directory.  Start JDeveloper, navigate to the BookLocator.jws file, and open it.   It should look something like this: The Properties Namespace file contains the property definitions and property set definitions you define.  It is explained more in detail in the Namespace documentation.  Although this example doesn't show it, the property set definitions have the ability to reference multiple locators per property.   This can be done by right-clicking on the 'Locator Info' box.  Configure the contents of the Locator Map  by editing locators and mapping them to available property names in the property set definition. Compiling, deploying, and running your locator The rest of the steps in this tutorial basically follow those in the previous blog on custom locators, and won't be repeated here.   A scenario to invoke your locator is included with the sample app: see BookProperties.scenarios_diagram above.  Summary This post demonstrates a simple library of books accessed by the BookPropertyLocator via the DAO layer.  This is a useful pattern for more realistic property retrievals, such as a backing user store.  It also points out the possibility of retrieving properties from multiple locators, which would be quite handy to retrieve user attributes from multiple sources.

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• Was I wrong about JavaScript?

  - by jboyer

  Yes, I was. Recently, I’ve taken a good hard look at JavaScript. I’ve used it before but mostly in the capacity of web design. Using JQuery to make your web page do cool stuff is different than really creating a JavaScript application using all of the language constructs. What I’m finding as I use it more is that I may have been wrong about my assumptions about it. Let me explain.   I enjoyed doing cool stuff with JQuery but the limited experience with JavaScript as a language coupled with the bad things that I heard about it led me to not have any real interest in it. However, JavaScript is ubiquitous on the web and if I want to do any web development, which I do, I need to learn it. So here I am, diving deep into the language with the help of the JavaScript Fundamentals training course at Pluralsight (great training for a low price) and the JavaScript: The Good Parts book by Douglas Crockford.   Now, there are certainly parts of JavaScript that are bad. I think these are well known by any developer that uses it. The parts that I feel are especially egregious are the following: The global object null vs. undefined truthy and falsy limited (nearly nonexistent) scoping ‘==’ and ‘===’ (I just don’t get the reason for coercion)   However, what I am finding hiding under the covers of the bad things is a good language. I am finding that I am legitimately enjoying JavaScript. This I was not expecting. I’m not going to go into a huge dissertation on what I like about it, but some things include: Object literal notation dynamic typing functional style (JavaScript: The Good Parts describes it as LISP in C clothing) JSON (better than XML) There are parts of JavaScript that seem strange to OOP developers like myself. However, just because it is different or seems strange does not mean it is bad. Some differences are quite interesting and useful.   I feel that it is important for developers to challenge their assumptions and also to be able to admit when they are wrong on a topic. Many different situations can arise that lead to this, such as choosing the wrong technology for a problem’s solution, misunderstanding the requirements, etc. I decided to challenge my assumptions about JavaScript instead of moving straight into CoffeeScript or Dart. After exploring it, I find that I am beginning to enjoy it the more I use it. As long as there are those like Crockford to help guide me in the right way to code in JavaScript, I can create elegant and efficient solutions to problems and add another ‘arrow’ to the ‘quiver’, so to speak. I do still intend to learn CoffeeScript to see what the hub-bub is about, but now I no longer have to be afraid of JavaScript as a legitimate programming language.   Has something similar ever happened to you? Tell me about it in the comments below.

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• Styling Windows Phone Silverlight Applications

  - by Tim Murphy

  If you have not developed with styles in Silverlight/XAML then it can be challenging and resources can be sparse depending on how deep you get.  One thing that you need to understand is what level you can apply styles and how much they can cascade.  What I am finding is that this doesn’t go to the level that we are used to in HTML and CSS. While styles can be defined at a page level if you want to share styles throughout your application they should be defined in the App.xaml file.  This is of course analogous to placing a style in your HTML file versus an external CSS file.  This is the type of style I will concentrate on in this post. The first thing to look it how styles associate to elements.  TargetType defines the object type that your style will apply to.  In the example below the style is targeting the TextBlock object type. <Style x:Key="TextBlockSmallGray" TargetType="TextBlock"> Next we use a Setter which allows you to apply values for specific attributes of the target object type.  The setters can be a simple value or complex.  The first example here is simply applying a color to the background property of the target. <Setter Property="Background" Value="White"/> The second setter example here is for the same property, but we are applying a the definition of a LinearGradientBrush. <Setter Property="Background"> <Setter.Value> <LinearGradientBrush> <GradientStop Offset="0" Color="Black"/> <GradientStop Offset="1" Color="White"/> </LinearGradientBrush> </Setter.Value> </Setter> The last thing I want to cover here is that you can leverage the system styles and then override or extend them.  The BasedOn attribute of the Style tag allows this sort of inheritance.  In the example below I am going to start with the PhoneTextTitleStyle and then override properties as needed. <Style x:Key="TextBlockTitle" BasedOn="{StaticResource PhoneTextTitle1Style}" TargetType="TextBlock"> So now that we have our styles defined applying it is fairly straight forward.  Add the style name as a static resource to the style property of the element in your page and off you go. <Grid x:Name="LayoutRoot" Style="{StaticResource PageGridStyle}"> So this is one step in creating consistency in your application’s look.  In future posts I will dig a little deeper. del.icio.us Tags: windows phone 7,mobile development,windows phone 7 development,.NET,software development,design,UX

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• Jitter during wall collisions with Bullet Physics: contact/penetration tolerance?

  - by Niriel

  I use the bullet physics engine through Panda3d. My scene is still very simple, think 'Wolfenstein3d': tile-based, walls are solid cubes. I expect walls to block the player, and I expect the player to slide along the walls in case of non-normal incidence. What I get is what I expect, with one difference: there is some jitter. If I try to force myself into the wall, then I see the frames blinking quickly between two positions. These differ by about 0.04 units of distance, which corresponds to 4 cm in my game. I noticed a 4 cm elsewhere: the bottom of my player capsule is 4 cm below ground, when at rest. Does that mean that there is somewhere in the Bullet engine a default 0.04-units-long tolerance to differentiate contact from collision? If so, what should I do ? Should I change the scale of my game so that these 0.04 units correspond to 0.4 cm, making the jitter ten times smaller? Or can I ask bullet to change its tolerance to a smaller value? Edit This is the jitter I get: 6.155 - 6.118 = 0.036 LPoint3f(0, 6.11694, 0.835) LPoint3f(0, 6.15499, 0.835) LPoint3f(0, 6.11802, 0.835) LPoint3f(0, 6.15545, 0.835) LPoint3f(0, 6.11817, 0.835) LPoint3f(0, 6.15726, 0.835) LPoint3f(0, 6.11876, 0.835) LPoint3f(0, 6.15911, 0.835) LPoint3f(0, 6.11937, 0.835) I found a setMargin method. I set it to 5 mm both on the BoxShape for the walls and on the Capsule shape for the player. It still jitters by about 35 mm as illustrated by this log (11.117 - 11.082 = 0.035): LPoint3f(0, 11.0821, 0.905) LPoint3f(0, 11.1169, 0.905) LPoint3f(0, 11.082, 0.905) LPoint3f(0, 11.117, 0.905) LPoint3f(0, 11.082, 0.905) LPoint3f(0, 11.117, 0.905) LPoint3f(0, 11.0821, 0.905) LPoint3f(0, 11.1175, 0.905) LPoint3f(0, 11.0822, 0.905) LPoint3f(0, 11.1178, 0.905) LPoint3f(0, 11.0823, 0.905) LPoint3f(0, 11.1183, 0.905) The margin on the capsule did change my penetration with the floor though, I'm a bit higher (0.905 instead of 0.835). However, it did not change anything when colliding with the walls. How can I make the collisions against the walls less jittery? Edit, the day after: After more investigation, it appears that dynamic objects behave well. My problem comes from the btKinematicCharacterController that I use for moving my character; that stuff is totally bugged, according to the whole Internet :/.

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• ArchBeat Link-o-Rama for 2012-10-12

  - by Bob Rhubart

  This is your brain on IT architecture. Oracle Technology Network Architect Day in Los Angeles, Oct 25 This is your brain on IT architecture. Stuff your cranium with architecture by attending Oracle Technology Network Architect Day in Los Angeles, October 25, 2012, at the Sofitel Los Angeles, 8555 Beverly Boulevard, Los Angeles, CA 90048. Technical sessions, panel Q&A, and peer roundtables--plus a free lunch. Register now. WebCenter Sites Gadget Development Concepts Quickstart | John Brunswick What are Gadgets? "At their most basic level they can be thought of as lightweight portlets that run largely on the client side of an architecture," says John Brunswick. "Gadgets provide a cross-platform container to run reusable UI modules that generally expose dynamic information to an end user, allowing for some level of end user customization." ORCLville: OOW 2012 - A Not So Brief Recap Oracle ACE Director Floyd Teter, an Applications & Apps Technology specialists, shares his personal, frank, and and extensive recap or Oracle OpenWorld 2012. Fusion Applications Technical Tips | Naveen Nahata "Setting memory parameters for Admin and Managed servers of various domains in Fusion Applications can be, let us say, a little daunting," says Oracle Fusion Middleware A-Team member Naveen Nahata. "While all this may look complicated and intimidating, it is actually relatively simple once you understand how it all works." Following the Thread in OSB | Antony Reynolds Antony Reynolds recently led an Oracle Service Bus POC in which his team needed to get high throughput from an OSB pipeline. "Imagine our surprise when, on stressing the system, we saw it lock up, with large numbers of blocked threads." He shares the details of the problem and the solution in this extensive technical post. ExaLogic Hackers Night - November 19th Nürnberg Germany | WebLogic Partner Community EMEA Want to get your hands on Oracle Exalogic? Make your way to Nürnberg, Germany for this Exalogic Hacker's Night on November 19, 2012. Experts will be on hand to help you test your ideas. (The blog post is in English, but the event registration page is in German.) Thought for the Day "A foolish consistency is the hobgoblin of little minds…" — Ralph Waldo Emerson (May 25, 1803 – April 27, 1882) Source: SoftwareQuotes.com

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• Sharing on Github

  - by Alan

  Over the past couple weeks I have gotten a lot of help from StackOverflow users on a project, and rather than keep the finished product to myself I wanted to share it unencumbered by licenses, but don't want there to be so much legwork during installation that users shy away from trying it. I am about to post it to Github and choosing public domain licensing. I would like to to be super simple for users to make use of and just FTP it up and go. That being said, do I need to make sure I remove things like the JQuery file, and other GPL / MIT licensed dependencies that I didn't write but that my code depends on? I haven't removed any copyright notices from the other code and all of it open source, it would just be nice if users could download everything at once while of course not trying to represent that I am the license holder of the dependencies. Inside my files are also some snippets, do those have to be externalized with installation instructions or can it be posted as is? Here is an example, my nav.php file is 115 lines long and I have these at the top: <script type="text/javascript" src="./js/ddaccordion.js"> /*********************************************** * Accordion Content script- (c) Dynamic Drive DHTML code library (www.dynamicdrive.com) * Visit http://www.dynamicDrive.com for hundreds of DHTML scripts * This notice must stay intact for legal use ***********************************************/ </script> <link href="css/admin.css" rel="stylesheet"> <script type="text/javascript"> ddaccordion.init({ headerclass: "submenuheader", //Shared CSS class name of headers group contentclass: "submenu", //Shared CSS class name of contents group revealtype: "click", //Reveal content when user clicks or onmouseover the header? Valid value: "click", "clickgo", or "mouseover" mouseoverdelay: 200, //if revealtype="mouseover", set delay in milliseconds before header expands onMouseover collapseprev: false, //Collapse previous content (so only one open at any time)? true/false defaultexpanded: [], //index of content(s) open by default [index1, index2, etc] [] denotes no content onemustopen: false, //Specify whether at least one header should be open always (so never all headers closed) animatedefault: false, //Should contents open by default be animated into view? persiststate: true, //persist state of opened contents within browser session? toggleclass: ["", ""], //Two CSS classes to be applied to the header when it's collapsed and expanded, respectively ["class1", "class2"] togglehtml: ["suffix", "<img src='./images/plus.gif' class='statusicon' />", "<img src='./images/minus.gif' class='statusicon' />"], //Additional HTML added to the header when it's collapsed and expanded, respectively ["position", "html1", "html2"] (see docs) animatespeed: "fast", //speed of animation: integer in milliseconds (ie: 200), or keywords "fast", "normal", or "slow" oninit:function(headers, expandedindices){ //custom code to run when headers have initalized //do nothing }, onopenclose:function(header, index, state, isuseractivated){ //custom code to run whenever a header is opened or closed //do nothing } }) </script>

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• Investment scheme for a PC game the project

  - by Alex Kamen

  Good day everyone, I am working on a PC game project that has 3 phases planned, micro, macro and mmo versions [if confused, see a brief description at the bottom]. I have found a potential investor for the micro version of the game, but naturally, he requested a detailed plan of how the game will pay back. And the problem is that micro version itself is not supposed to be monetized much, other than some ads and limited in-game currency utilization. The idea is that with this combat demo already at hand, it should be possible to get a really large enough investment (millions of dollars) and use it to pay back the initial small one (thousands of dollars) and take the project into macro phase, which will really make profit. This way, everybody is going to win, provided that I can deliver the end-product. Yet while I am confident of that both the conception of the macro and the real game-play of the micro versions are going to be appealing, I don’t know how to obtain any guarantee of that I will be able to get funded once I have the prototype ready. And without that, I won’t receive the funds for the prototype in the first place! To summarize, my question is: how to figure out my future possibilities of getting funded once I have combat demo out, basically “whom to write to and what”. Ideally, I would like some sort of a preliminary agreement with a game publisher, something that would basically state “If the developer provides the product in time and in quality corresponding to the specifications given, the publisher guarantees to allocate funds for distribution and further development, thereby acquiring the right to X part of all future profits”. Does this sound sane? It’s just that I don’t want to sell all of my rights out straight away by taking a big outside investment while the project is in such early stage. I would appreciate if you would share your thoughts on this kind of scheme, and be sure to ask questions as I am sure I must have forgotten to mention a ton of important things, like the fact that initial funds are going to be spent on outsourcing (living in Siberia is really just great). [here’s a brief outline of what each version will feature] [micro] 1) turn based tactical combat rules 2) character development 3) arena/tournament system [macro] 4) ai-ruled dynamic interactive worlds 5) global map adventuring 6) strategic rpg + god simulator gameplay [mmo] 7) Persistent worlds system 8) Social structures system (“guilds/clans”) 9) god-simulation on the mmo scale P.S. Obviously, these features are incremental, so that mmo version has all 9.

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• Segmentation and Targeting: Your Tools for Personalizing the Online Customer Experience

  - by Christie Flanagan

  In order to deliver the kind of personalized and engaging online experiences that customers expect today, look to segmentation and targeting.  Segmentation is the practice of dividing your site visitors into distinct groups based on shared characteristics or behavior – for example, a segment may consist of site visitors who have visited pages related to certain product type, or they may consist of visitors within the same age group or geographic area.  The idea is that those within a segment are more likely to have common needs, problems or interests that can be served by your business. Targeting is the process by which the most relevant content, whether an article promotion or other piece of content, is delivered to your visitors based on their segment membership. Segmentation and targeting are used to drive greater engagement on your web presence by delivering content to your site visitors that is tailored to their interests, behavior or other attributes.  You may have a number of different goals for your segmentation and targeting efforts: Up-sell or cross-sell to your customers Conduct A/B testing on your offers and creative Offer discounts, promotions or other incentives for the time and duration that you specify Make is easier to find relevant information about products and services Create premium content model There are two different approaches you can take toward segmentation and targeting for you online customer experience initiatives. The first is more of a manual process, in which marketers manage the process of determining which segments to create and which content to target to those segments. The benefit of this approach is that it gives marketers a high level of control over the whole process which works well when you have a thorough understanding of your segments and which content is most likely to serve their needs.  Tools for marketer managed segmentation and targeting are often built right in to your WEM platform, as they are with Oracle WebCenter Sites. The downside is that the more segments and content that you have, the more time consuming and complicated in can be to manage manually.The second approach relies on predictive intelligence to automate the segmentation and targeting process.  This allows optimization of the process to occur in real time. This approach helps reduce the burden of manual segmentation and targeting and can result in new insights into segments that you may never have thought of on your own.  It also provides you with the capability to quickly test new offers and promotions on your site.  Predictive segmentation and targeting can be achieved by using Oracle WebCenter Sites and Oracle Real-Time Decisions together. *****Get a taste for how Oracle WebCenter Sites and Oracle Real-Time Decisions combine to deliver powerful capabilities for predictive segmentation and targeting by watching this on demand webcast introducing Oracle WebCenter Sites 11g or by reading IDC’s take on the latest release of Oracle’s web experience management solution.  Be sure to return to the Oracle WebCenter blog on Thursday for a closer look at how to optimize the online customer experience using these two products together.

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• Event Driven Behavior Tree: deterministic traversal order with parallel

  - by Heisenbug

  I've studied several articles and listen some talks about behavior trees (mostly the resources available on AIGameDev by Alex J. Champandard). I'm particularly interested on event driven behavior trees, but I have still some doubts on how to implement them correctly using a scheduler. Just a quick recap: Standard Behavior Tree Each execution tick the tree is traversed from the root in depth-first order The execution order is implicitly expressed by the tree structure. So in the case of behaviors parented to a parallel node, even if both children are executed during the same traversing, the first leaf is always evaluated first. Event Driven BT During the first traversal the nodes (tasks) are enqueued using a scheduler which is responsible for updating only running ones every update The first traversal implicitly produce a depth-first ordered queue in the scheduler Non leaf nodes stays suspended mostly of the time. When a leaf node terminate(either with success or fail status) the parent (observer) is waked up allowing the tree traversing to continue and new tasks will be enqueued in the scheduler Without parallel nodes in the tree there will be up to 1 task running in the scheduler Without parallel nodes, the tasks in the queue(excluding dynamic priority implementation) will be always ordered in a depth-first order (is this right?) Now, from what is my understanding of a possible implementation, there are 2 requirements I think must be respected(I'm not sure though): Now, some requirements I think needs to be guaranteed by a correct implementation are: The result of the traversing should be independent from which implementation strategy is used. The traversing result must be deterministic. I'm struggling trying to guarantee both in the case of parallel nodes. Here's an example: Parallel_1 -->Sequence_1 ---->leaf_A ---->leaf_B -->leaf_C Considering a FIFO policy of the scheduler, before leaf_A node terminates the tasks in the scheduler are: P1(suspended),S1(suspended),leaf_A(running),leaf_C(running) When leaf_A terminate leaf_B will be scheduled (at the end of the queue), so the queue will become: P1(suspended),S1(suspended),leaf_C(running),leaf_B(running) In this case leaf_B will be executed after leaf_C at every update, meanwhile with a non event-driven traversing from the root node, the leaf_B will always be evaluated before leaf_A. So I have a couple of question: do I have understand correctly how event driven BT work? How can I guarantee the depth first order is respected with such an implementation? is this a common issue or am I missing something?

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• Need help on a problemset in a programming contest

  - by topher

  I've attended a local programming contest on my country. The name of the contest is "ACM-ICPC Indonesia National Contest 2013". The contest has ended on 2013-10-13 15:00:00 (GMT +7) and I am still curious about one of the problems. You can find the original version of the problem here. Brief Problem Explanation: There are a set of "jobs" (tasks) that should be performed on several "servers" (computers). Each job should be executed strictly from start time Si to end time Ei Each server can only perform one task at a time. (The complicated thing goes here) It takes some time for a server to switch from one job to another. If a server finishes job Jx, then to start job Jy it will need an intermission time Tx,y after job Jx completes. This is the time required by the server to clean up job Jx and load job Jy. In other word, job Jy can be run after job Jx if and only if Ex + Tx,y = Sy. The problem is to compute the minimum number of servers needed to do all jobs. Example: For example, let there be 3 jobs S(1) = 3 and E(1) = 6 S(2) = 10 and E(2) = 15 S(3) = 16 and E(3) = 20 T(1,2) = 2, T(1,3) = 5 T(2,1) = 0, T(2,3) = 3 T(3,1) = 0, T(3,2) = 0 In this example, we need 2 servers: Server 1: J(1), J(2) Server 2: J(3) Sample Input: Short explanation: The first 3 is the number of test cases, following by number of jobs (the second 3 means that there are 3 jobs for case 1), then followed by Ei and Si, then the T matrix (sized equal with number of jobs). 3 3 3 6 10 15 16 20 0 2 5 0 0 3 0 0 0 4 8 10 4 7 12 15 1 4 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 4 8 10 4 7 12 15 1 4 0 50 50 50 50 0 50 50 50 50 0 50 50 50 50 0 Sample Output: Case #1: 2 Case #2: 1 Case #3: 4 Personal Comments: The time required can be represented as a graph matrix, so I'm supposing this as a directed acyclic graph problem. Methods I tried so far is brute force and greedy, but got Wrong Answer. (Unfortunately I don't have my code anymore) Could probably solved by dynamic programming too, but I'm not sure. I really have no clear idea on how to solve this problem. So a simple hint or insight will be very helpful to me.

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• WHERE x = @x OR @x IS NULL

  - by steveh99999

  Every SQL DBA and developer should read the blog of MVP Erland Sommarskog – but particularly  his article on dynamic search conditions in T-SQL. I’ve linked above to his SQL 2005 article but his 2008 version is also a must-read. I seem to regularly come across uses of the SQL in the title above… Erland’s article explains in detail why this is inefficient, but I came across a nice example recently… A stored procedure contained the following code :- WHERE @Name is null or [Name] like @Name as a nonclustered index exists on the Name column, you might assume this would be handled efficiently by SQL Server. However, I got the following output from SET STATISTICS IO Table 'xxxxx'. Scan count 15, logical reads 47760, physical reads 9, read-ahead reads 13872, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0. Note the high number of logical reads… After a bit of investigation, we found that @Name could never actually be set to NULL in this particular example. ie the @x IS NULL was spurious… So, we changed the call to WHERE  [Name] like @Name Now, how much more efficient is this code ? Table 'xxxxx'. Scan count 3, logical reads 24, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0 A nice easy win in this case…… a full index scan has been replaced by a significantly more efficient index seek. I managed to recreate the same behaviour on Adventureworks – here’s a quick query to demonstrate :- USE adventureworks SET STATISTICS IO ON DECLARE @id INT = 51721 SELECT * FROM Sales.SalesOrderDetail WHERE @id IS NULL OR salesorderid = @id SELECT * FROM Sales.SalesOrderDetail WHERE salesorderid = @id Take a look at the STATISTICS IO output and compare the actual query plans used to prove the impact of  WHERE @id IS NULL. And just to follow some of Erland’s advice – here’s how you could get similar performance if it was possible that @id could actually sometimes contain NULL. DECLARE @sql NVARCHAR(4000), @parameterlist NVARCHAR(4000) DECLARE @id INT = 51721 – or change to NULL to prove query is functionally correct SET @sql = 'SELECT * FROM Sales.SalesOrderDetail WHERE 1 = 1' IF @id IS NOT NULL SET @sql = @sql + ' AND salesorderid = @id' IF @id IS NULL SET @sql = @sql + ' AND salesorderid IS NULL' SET @parameterlist = '@id INT' EXEC sp_executesql @sql, @parameterlist,@id Sometimes I think we focus too much on hardware and SQL Server configuration – when really the answer is focus on writing efficient SQL.

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