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  • couchdb: one database per account vs all in one database w. a namespace / property

    - by thruflo
    I'm modelling a document generation system in couchdb. It semi-automates the production of proposal and presentation documents from managable document fragments. Much like, say, Basecamp, it breaks down very simply into self-contained data per 'account'. Each account has multiple users, projects, documents, etc. However, nothing should be shared between accounts. I can see two ways of doing this: one couchdb database per account use a namespace / property to identify the account It seems to me that the first approach is conceptually sound and potentially has security and partitioning advantages. However, it seems to me to restrict some cross-database data querying (that I don't have a use case for now but you never know...) and to make updating views potentially require an awful lot of writes. Does anyone experienced with this kind of decision have any advice?

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  • I need to model my Javascript application

    - by Totty
    Hy, I was looking for a software to model an application, because is becoming too big. Like this: Class - A Methods - a, b, c, d, e Class - B Methods - a, b, c, d, e This should be in graphical mode, Classes are some boxes, and the methods are in the box. Then I would like to be able to make a arrow from one method to another. Do you know some good software? thanks

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  • When modeling a virtual circuit board, what is the best design pattern to check for cycles?

    - by Wallace Brown
    To make it simple assume you have only AND and OR gates. Each has two inputs and one output. The output of two inputs can be used as an input for the next gate For example: A AND B - E C AND D - F E OR F - G Assuming an arbitrary number of gates, we want to check if the circuit ever connects back into itself at an earlier state? For example: E AND F - A This should be illegal since it creates an endless cycle. What design pattern would best be able to check for these cycles?

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  • How can I create a 3D model in Java without using modeling software?

    - by Galen Nare
    I am a lightly experienced game developer and this is my first time trying 3D objects in Java for the first time. I have been recently creating and updating games using AWT, Swing, and Graphics, but I want to delve farther into Java. I have looked into Java3D, but it's not what I want. I want to use Images and then crop the Image and place the respective textures in their respective places. I already know how to do the cropping and 2D Image editing, but how do I go 3D?

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  • Does one's choice of 3d modeling software used during asset creation affect performance at runtime?

    - by user134143
    Does software used to create 3d assets (for game development specifically) have an impact on the efficiency of the program? In other words, is it possible to reduce the operating footprint of an application merely by utilizing alternative development software during production of 3d assets? If you use two different applications to create a 3-dimensional image of a box, can one of them result in better performance if aspects of the image are identical? I am attempting to get the information I need without causing unnecessary debate over specific software choice.

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  • How Do You Actually Model Data?

    Since the 1970’s Developers, Analysts and DBAs have been able to represent concepts and relations in the form of data through the use of generic symbols.  But what is data modeling?  The first time I actually heard this term I could not understand why anyone would want to display a computer on a fashion show runway. Hey, what do you expect? At that time I was a freshman in community college, and obviously this was a long time ago.  I have since had the chance to learn what data modeling truly is through using it. Data modeling is a process of breaking down information and/or requirements in to common categories called objects. Once objects start being defined then relationships start to form based on dependencies found amongst other existing objects.  Currently, there are several tools on the market that help data designer actually map out objects and their relationships through the use of symbols and lines.  These diagrams allow for designs to be review from several perspectives so that designers can ensure that they have the optimal data design for their project and that the design is flexible enough to allow for potential changes and/or extension in the future. Additionally these basic models can always be further refined to show different levels of details depending on the target audience through the use of three different types of models. Conceptual Data Model(CDM)Conceptual Data Models include all key entities and relationships giving a viewer a high level understanding of attributes. Conceptual data model are created by gathering and analyzing information from various sources pertaining to a project during the typical planning phase of a project. Logical Data Model (LDM)Logical Data Models are conceptual data models that have been expanded to include implementation details pertaining to the data that it will store. Additionally, this model typically represents an origination’s business requirements and business rules by defining various attribute data types and relationships regarding each entity. This additional information can be directly translated to the Physical Data Model which reduces the actual time need to implement it. Physical Data Model(PDMs)Physical Data Model are transformed Logical Data Models that include the necessary tables, columns, relationships, database properties for the creation of a database. This model also allows for considerations regarding performance, indexing and denormalization that are applied through database rules, data integrity. Further expanding on why we actually use models in modern application/database development can be seen in the benefits that data modeling provides for data modelers and projects themselves, Benefits of Data Modeling according to Applied Information Science Abstraction that allows data designers remove concepts and ideas form hard facts in the form of data. This gives the data designers the ability to express general concepts and/or ideas in a generic form through the use of symbols to represent data items and the relationships between the items. Transparency through the use of data models allows complex ideas to be translated in to simple symbols so that the concept can be understood by all viewpoints and limits the amount of confusion and misunderstanding. Effectiveness in regards to tuning a model for acceptable performance while maintaining affordable operational costs. In addition it allows systems to be built on a solid foundation in terms of data. I shudder at the thought of a world without data modeling, think about it? Data is everywhere in our lives. Data modeling allows for optimizing a design for performance and the reduction of duplication. If one was to design a database without data modeling then I would think that the first things to get impacted would be database performance due to poorly designed database and there would be greater chances of unnecessary data duplication that would also play in to the excessive query times because unneeded records would need to be processed. You could say that a data designer designing a database is like a box of chocolates. You will never know what kind of database you will get until after it is built.

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  • Are there any modeling tools that can visually generate jpa or sql queries?

    - by Shervin
    Does anyone know of a tool like PowerArchitect or SquirrelSQL or maybe eclipse plugin that lets you also generate jpa/sql queries? Imagine you choosing your database, or your entity beans, and the modeling would reverse engineer your database/entity model, so that you could visually just choose the columns you wanted to select, and it would generate jpa or sql queries for you. For instance choosing A.b and X.y would generate something like this: select a.b, x.y from A a, X x join ......

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  • What&rsquo;s new in VS.10 &amp; TFS.10?

    - by johndoucette
    Getting my geek on… I have decided to call the products VS.10 (Visual Studio 2010), TP.10 (Test Professional 2010),  and TFS.10 (Team Foundation Server 2010) Thanks Neno Loje. What's new in Visual Studio & Team Foundation Server 2010? Focusing on Visual Studio Team System (VSTS) ALM-related parts: Visual Studio Ultimate 2010 NEW: IntelliTrace® (aka the historical debugger) NEW: Architecture Tools New Project Type: Modeling Project UML Diagrams UML Use Case Diagram UML Class Diagram UML Sequence Diagram (supports reverse enginneering) UML Activity Diagram UML Component Diagram Layer Diagram (with Team Build integration for layer validation) Architecuture Explorer Dependency visualization DGML Web & Load Tests Visual Studio Premium 2010 NEW: Architecture Tools Read-only model viewer Development Tools Code Analysis New Rules like SQL Injection detection Rule Sets Code Profiler Multi-Tier Profiling JScript Profiling Profiling applications on virtual machines in sampling mode Code Metrics Test Tools Code Coverage NEW: Test Impact Analysis NEW: Coded UI Test Database Tools (DB schema versioning & deployment) Visual Studio Professional 2010 Debuger Mixed Mode Debugging for 64-bit Applications Export/Import of Breakpoints and data tips Visual Studio Test Professional 2010 Microsoft Test Manager (MTM, formerly known as "Camano")) Fast Forward Testing Visual Studio Team Foundation Server 2010 Work Item Tracking and Project Management New MSF templatesfor Agile and CMMI (V 5.0) Hierarchical Work Items Custom Work Item Link Types Ready to use Excel agile project management workbooks for managing your backlogs (including capacity planing) Convert Work Item query to an Excel report MS Excel integration Support for Work Item hierarchies Formatting is preserved after doing a 'Refresh' MS Project integration Hierarchy and successor/predecessor info is now synchronized NEW: Test Case Management Version Control Public Workspaces Branch & Merge Visualization Tracking of Changesets & Work Items Gated Check-In Team Build Build Controllers and Agents Workflow 4-based build process NEW: Lab Management (only a pre-release is avaiable at the moment!) Project Portal & Reporting Dashboards (on SharePoint Portal) Burndown Chart TFS Web Parts (to show data from TFS) Administration & Operations Topology enhancements Application tier network load balancing (NLB) SQL Server scale out Improved Sharepoint flexibility Report Server flexibility Zone support Kerberos support Separation of TFS and SQL administration Setup Separate install from configure Improved installation wizards Optional components Simplified account requirements Improved Reporting Services configuration Setup consolidation Upgrading from previous TFS versions Improved IIS flexibility Administration Consolidation of command line tools User rename support Project Collections Archive/restore individual project collections Move Team Project Collections Server consolidation Team Project Collection Split Team Project Collection Isolation Server request cancellation Licensing: TFS server license included in MSDN subscriptions Removed features (former features not part of Visual Studio 2010): Debug » Start With Application Verifier Object Test Bench IntelliSense for C++ / CLI Debugging support for SQL 2000

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  • Managed Service Architectures Part I

    - by barryoreilly
    Instead of thinking about service oriented architecture, a concept that is continually defined, redefined, abused and mistreated, perhaps it is time to drop the acronym and consider what we actually need to get the job done.   ‘Pure’ SOA involves the modeling of an organisation’s processes, the so called ‘Top Down’ approach, followed by the implementation of these processes as services.     Another approach, more commonly seen in the wild, is the bottom up approach. This usually involves services that simply start popping up in the organization, and SOA in this case is often just an attempt to rein in these services. Such projects, although described as SOA projects for a variety of reasons, have clearly little relation to process driven architecture. Much has been written about these two approaches, with many deciding that a hybrid of both methods is needed to succeed with SOA.   These hybrid methods are a sensible compromise, but one gets the feeling that there is too much focus on ‘Succeeding with SOA’. Organisations who focus too much on bottom up development, or who waste too much time and money on top down approaches that don’t produce results, are often recommended to attempt an ‘agile’(Erl) or ‘middle-out’ (Microsoft) approach in order to succeed with SOA.  The problem with recommending this approach is that, in most cases, succeeding with SOA isn’t the aim of the project. If a project is started with the simple aim of ‘Succeeding with SOA’ then the reasons for the projects existence probably need to be questioned.   There are a number of things we can be sure of: ·         An organisation will have a number of disparate IT systems ·         Some of these systems will have redundant data and functionality ·         Integration will give considerable ROI ·         Integration will already be under way. ·         Services will already exist in the organisation ·         These services will be inconsistent in their implementation and in their governance   So there are three goals here: 1.       Alignment between the business and IT 2.     Integration of disparate systems 3.     Management of services.   2 and 3 are going to happen,  in fact they must happen if any degree of return is expected from the IT department. Ignoring 1 is considered a typical mistake in SOA implementations, as it ignores the business implications. However, the business implication of this approach is the money saved in more efficient IT processes. 2 and 3 are ongoing, and they will continue happening, even if a large project to produce a SOA metamodel is started. The result will then be an unstructured cackle of services, and a metamodel that is already going out of date. So we get stuck in and rebuild our services so that they match the metamodel, with the far reaching consequences that this will have on all our LOB systems are current. Lets imagine that this actually works ( how often do we rip and replace working software because it doesn't fit a certain pattern? Never -that's the point of integration), we will now be working with a metamodel that is out of date, and most likely incomplete if the organisation is large.      Accepting that an object can have more than one model over time, with perhaps more than one model being  at any given time will help us realise the limitations of the top down model. It is entirely normal , and perhaps necessary, for an organisation to be able to view an entity from different perspectives.   So, instead of trying to constantly force these goals in a straight line, why not let them happen in parallel, and manage the changes in each layer.     If  company A has chosen to model their business processes and create a business architecture, there will be a reason behind this. Often the aim is to make the business more flexible and able to cope with change, through alignment between the business and the IT department.   If company B’s IT department recognizes the problem of wild services springing up everywhere, and decides to do something about it, by designing a platform and processes for the introduction of services, is this not a valid approach?   With the hybrid approach, it is recommended that company A begin deploying services as quickly as possible. Based on models that are clearly incomplete, and which will therefore change rapidly and often in the near future. Natural business evolution will also mean that the models can be guaranteed to change in the not so near future. To ‘Succeed with SOA’ Company B needs to go back to the drawing board and start modeling processes and objects. So, in effect, we are telling business analysts to start developing code based on a model they are unsure of, and telling programmers to ignore the obvious and growing problems in their IT department and start drawing lines and boxes.     Could the problem be that there are two different problem domains? And the whole concept of SOA as it being described by clever salespeople today creates an example of oft dreaded ‘tight coupling’ between these two domains?   Could it be that we have taken two large problem areas, and bundled the solution together in order to create a magic bullet? And then convinced ourselves that the bullet actually exists?   Company A wants to have a closer relationship between the business and its IT department, in order to become a more flexible organization. Company B wants to decrease the maintenance costs of its IT infrastructure. If both companies focus on succeeding with SOA, then they aren’t focusing on their actual goals.   If Company A starts building services from incomplete models, without a gameplan, they will end up in the same situation as company B, with wild services. If company B focuses on modeling, they could easily end up with the same problems as company A.   Now we have two companies, who a short while ago had one problem each, that now have two problems each. This has happened because of a focus on ‘Succeeding with SOA’, rather than solving the problem at hand.   This is not to suggest that the two problem domains are unrelated, a strategy that encompasses both will obviously be good for the organization. But only if the organization realizes this and can develop such a strategy. This strategy cannot be bought in a box.       Anyone who has worked with SOA for a while will be used to analyzing the solutions to a problem and judging the solution’s level of coupling. If we have two applications that each perform separate functions, but need to communicate with each other, we create a integration layer between them, perhaps with a service, but we do all we can to reduce the dependency between the two systems. Using the same approach, we can separate the modeling (business architecture) and the service hosting (technical architecture).     The business architecture describes the processes and business objects in the business domain.   The technical architecture describes the hosting and management and implementation of services.   The glue that binds these together, the integration layer in our analogy, is the service contract, where the operations map the processes to their technical implementation, and the messages map business concepts to software objects in the implementation.   If we reduce the coupling between these layers, we should be able to allow developers to develop services, and business analysts to develop models, without the changes rippling through from one side to the other.   This would allow company A to carry on modeling, and company B to develop a service platform, each achieving their intended goal, without necessarily creating the problems seen in pure top down or bottom up approaches. Company B could then at a later date map their service infrastructure to a unified model, and company A could carry on modeling, insulating deployed services from changes in the ongoing modeling.   How do we do this?  The concept of service virtualization has been around for a while, and is instantly realizable in Microsoft’s Managed Services Engine. Here we can create a layer of virtual services, which represent the business analyst’s view, presenting uniform contracts to the outside world. These services can then transform and route messages to the actual service implementations. I like to think of the virtual services with their beautifully modeled interfaces as ‘SOA services’, and the implementations as simple integration ‘adapter’ services providing an interface to a technical implementation. The Managed Services Engine also provides policy based control over services, regardless of where they are deployed, simplifying handling of security, logging, exception handling etc.   This solves a big problem. The pressure to deliver services quickly is always there in projects. It is very important to quickly show value when implementing service architectures. There is also pressure to deliver quality, and you can’t easily do both at the same time. This approach allows quick delivery with quality increasing over time, allowing modeling and service development to occur in parallel and independent of each other. The link between business modeling and service implementation is not one that is obvious to many organizations, and requires a certain maturity to realize and drive forward. It is also completely possible that a company can benefit from one without the other, even if this approach is frowned upon today, there are many companies doing so and seeing ROI.   Of course there are disadvantages to this. The biggest one being the transformations necessary between the virtual interfaces and the service implementations. Bad choices in developing the services in the service implementation could mean that it is impossible to map the modeled processes to the implementation with redevelopment of the service. In many cases the architect will not have a choice here anyway, as proprietary systems are often delivered with predeveloped services. The alternative is to wait until the model is finished and then build the service according the model. However, if that approach worked we wouldn’t be having this discussion! And even when it does work, natural business evolution will mean that the two concepts (model and implementation) will immediately start to drift away from each other, so coupling them tightly together so that they are forever bound to the model that only applies at the time of the modeling work will not really achieve a great deal. Architecture is all about trade offs, and here a choice has to be made. The choice is between something will initially be of low quality but will work, or something that may well be impossible to achieve in most situations.         In conclusion, top-down is a natural approach for business analysts, and bottom-up  is a natural approach for developers. Instead of trying to force something on both that neither want, and which has not shown itself to be successful,  why not let them get on with their jobs, and let an enterprise architect coordinate the processes?

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  • What is the best way to diagrammatically represent a system threading architecture?

    - by thegreendroid
    I am yet to find the perfect way to diagrammatically represent the overall threading architecture for a system (using UML or otherwise). I am after a diagramming technique that would show all the threads in a given system and how they interact with each other. There are a few similar questions - Drawing Thread Interaction, UML Diagrams of Multithreaded Applications and Intuitive UML Approach to Depict Threads but they don't fully answer my question. What are some of the techniques that you've found useful to depict the overall threading architecture for a system?

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  • Investigating a big C++ project from its source code [closed]

    - by user827992
    Possible Duplicate: What is the best method to start understanding BIG project source code? I have a project that I would like to dissect to learn something new from it. This project is about 200 megabytes. For me, it is just impossible to open every cpp and hpp file and read each and every one. I also don't know what is the best approach in this case. Many people on the internet are looking for an UML tool to generate some kind of graph. I think that UML works well when you are starting a project and you want to express the business logic of your classes and methods. In my opinion UML is totally useless when studying a project only from its source code. Also UML is an OO language, in a large sized C++ project I find a lot of stuff that is not an object and can express some other kind of paradigm. Can you name a tool or a class of software that can help with this?

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  • collectd does not work

    - by bery
    I have installed collectd-5.0.0 on Fedora12 server and would like to run its service for receiving data from clients. I have enabled network plugin and rddtool plugin as commented: collectd.conf in server: BaseDir "/opt/collectd/var/lib/collectd" LoadPlugin "logfile" LoadPlugin network LoadPlugin rrdtool <Plugin network> Listen "192.168.8.37" "25826" </Plugin> collectd.conf in client: LoadPlugin logfile LoadPlugin cpu LoadPlugin network LoadPlugin memory <Plugin network> Server"192.168.8.37" "25826" </Plugin> collectd.log in server: [2011-08-03 02:36:04] Exiting normally. [2011-08-03 02:36:04] rrdtool plugin: Shutting down the queue thread. [2011-08-03 02:36:04] network plugin: Stopping receive thread. [2011-08-03 02:36:04] network plugin: Stopping dispatch thread. [2011-08-03 02:37:11] Initialization complete, entering read-loop. collectd.log in client: [2011-08-02 17:31:44] Initialization complete, entering read-loop. results thst execute netstat on server: netstat -ulpn | grep 25826 udp 0 0 192.168.8.37:25826 0.0.0.0:* 4744/collectd problem: but there is noting in "/opt/collectd/var/lib/collectd/" on ser yes,I move the port number of "25826" as your propose(But I think this is the default port for coolectd).there is no rdd files recived on server. collectd.log in client collectd [2011-08-03 10:01:36] plugin_read_thread: Handling memory'. [2011-08-03 10:01:36] plugin_read_thread: Handlingcpu'. [2011-08-03 10:01:36] plugin_dispatch_values: time = 1312380096.431; interval = 10.000; host = uml; plugin = memory; plugin_instance = ; type = memory; type_instance = used; [2011-08-03 10:01:36] plugin_dispatch_values: time = 1312380096.431; interval = 10.000; host = uml; plugin = cpu; plugin_instance = 0; type = cpu; type_instance = user; [2011-08-03 10:01:36] uc_update: uml/memory/memory-used: ds[0] = 280412160.000000 [2011-08-03 10:01:36] plugin: plugin_write: Writing values via network. [2011-08-03 10:01:36] uc_update: uml/cpu-0/cpu-user: ds[0] = 0.100008 [2011-08-03 10:01:36] plugin: plugin_write: Writing values via network. [2011-08-03 10:01:36] plugin_dispatch_values: time = 1312380096.431; interval = 10.000; host = uml; plugin = memory; plugin_instance = ; type = memory; type_instance = buffered; [2011-08-03 10:01:36] plugin_dispatch_values: time = 1312380096.431; interval = 10.000; host = uml; plugin = cpu; plugin_instance = 0; type = cpu; type_instance = nice; [2011-08-03 10:01:36] uc_update: uml/memory/memory-buffered: ds[0] = 344182784.000000 [2011-08-03 10:01:36] plugin: plugin_write: Writing values via network. [2011-08-03 10:01:36] uc_update: uml/cpu-0/cpu-nice: ds[0] = 0.000000 [2011-08-03 10:01:36] plugin: plugin_write: Writing values via network. [2011-08-03 10:01:36] network plugin: flush_buffer: send_buffer_fill = 1340 [2011-08-03 10:01:36] network plugin: network_send_buffer: buffer_len = 1340 ... [2011-08-03 10:01:36] plugin_read_thread: Next read of the cpu plugin at 1312380106.429064774. collectd.log in server collectd: [2011-08-03 20:18:08] type = network [2011-08-03 20:18:08] type = rrdtool [2011-08-03 20:18:08] network plugin: sockent_open: node = 192.168.8.37; service = 25826; [2011-08-03 20:18:08] fd = 3; calling bind' [2011-08-03 20:18:08] Done parsing/opt/collectd//share/collectd/types.db' [2011-08-03 20:18:08] interval_g = 10; [2011-08-03 20:18:08] timeout_g = 2; [2011-08-03 20:18:08] hostname_g = localhost.localdomain; [2011-08-03 20:18:08] Initialization complete, entering read-loop. It looks like, data is sending but doesn't be recived. Where is the mistake?

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  • Visual Studio 2010 Productivity Power Tool Extensions

    - by ScottGu
    Last month I blogged about the Extension Manager that is built-into VS 2010 – as well as about a cool VS 2010 PowerCommands extension that provides some extra features for Visual Studio.  The Visual Studio 2010 Extension Manager provides an easy way for developers to quickly find and install extensions and plugins that enhance the built-in functionality to VS 2010. New VS 2010 Productivity Power Tools Release Earlier this week Jason Zander announced the availability of a new VS 2010 Productivity Power Tools release that includes a bunch of great new VS 2010 extensions that provide a bunch of cool new functionality for you to take advantage of.  You can download and install the release for free here.  Some of the code editor improvements it provides include: Entire Line Highlighting: Makes it easier to track cursor location within the editor Entire Line Selection: Triple Clicking a line in the code editor now selects the entire line (like with MS Word) Code Block Movement: Use Alt+Up/Down Arrow now moves selected code blocks up/down in the editor Consistent Tabs vs. Spaces: Ensure consistent tab vs. space usage across your projects Colorized Parameters: It is now easier to see/identify method parameters Column Guide: You can now add vertical column guidelines to help with text alignment and sizes Align assignments: Makes it easier to line-up multiple variable assignments within your code HTML Clipboard Support: Copy/paste code from VS into an HTML buffer (useful for blogging!) Ctrl + Click Go to Definition: You can now hold down the Ctrl key and click a type to go to its definition It also includes several tab management improvements for managing document tabs within the IDE: Show Close Button in Tab Well: Shows a close button in document well for the active tab (like VS 2008 did) Colored Tabs: You can now select the color of each document tab by project or by regex Pinned Tabs: Enables you to pin tabs to keep them always visible and available Vertical Tabs: You can now show document tabs vertically to fit more tabs than normal Remove Tabs by Usage Order: Better behavior when adding new tabs and one needs to be hidden for space reasons Sort Tabs by Project: Tabs can be sorted by project they belong to, keeping them grouped together Sort Tabs Alphabetically: Tabs can be sorted alphabetically And last – but not least – it includes a new and improved “Add Reference” dialog: This new Add Reference dialog caches assembly information – which means it loads within a second or two (note: the very first time it still loads assembly data – but it then caches it and makes it fast afterwards). The new Add Reference dialog also now includes searching support – making it easier to find the assembly you are looking for. You can read more about all of the above improvements in Jason’s blog post about the release. New Visualization and Modeling Feature Pack Release Earlier this week we also shipped a new feature pack that adds additional modeling and code visualization features to VS 2010 Ultimate.  You can download it here. The Visualization and Modeling Feature Pack includes a bunch of great new capabilities including: Web Site Visualization: New support for generating a DGML visualization for ASP.NET projects C/C++ Native Code Visualization: New support for generating DGML diagrams for C/C++ projects Generate Code from UML Class Diagrams: You can now generate code from your UML diagrams Create UML Class Diagrams from Code: Create UML diagrams from existing code bases Import UML from XML: Import UML class, sequence, and use case elements from XMI 2.1 files Custom Validation Layer Rules: Write custom code to create, modify, and validate layer diagrams Jason’s blog post covers more about these features as well. Hope this helps, Scott P.S. In addition to blogging, I am also now using Twitter for quick updates and to share links. Follow me at: twitter.com/scottgu

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  • Removing Barriers to Create Effective Data Models

    After years of creating and maintaining data models, I have started to notice common barriers that decrease the accuracy and usefulness of models. In my opinion, the main causes of these barriers are the lack of knowledge and communication from within a company. The lack of knowledge in regards to data models or data modeling can take many forms. Company Culture Knowledge Whether documented or undocumented, existing business rules of a company can affect how data is modeled. For example, if a company only allows 1 assigned person per customer to be able to manipulate a customer’s record then then a data model that includes an associated table that joins customers and employee’s would be unneeded because that would allow for the possibility of multiple employees to handle a customer because of the potential for a many to many relationship between Customers and Employees. Technical Knowledge Depending on the data modeler’s proficiency in modeling data they can inadvertently cause issues and/or complications with a design without even noticing. It is important that companies share data modeling responsibilities so that the models are developed from multiple perspectives of a system, company and the original problem.  In addition, the tools that a company selects to create data models can also affect the accuracy of the model if designer are not familiar with the tools or the tools are too complex to use for the designer. Existing System Knowledge In order for a data modeler to model data for an existing system so that new changes can be applied to a system then they need to at least know the basic concepts of a system so that they can work within it. This will promote reusability of data and prevent the chance of duplicating data. Project Knowledge This should be pretty obvious, but it is very hard to create an accurate data model without knowing what data needs to be modeled. I have always found it strange that I have been asked to start modeling data prior to a client formalizing any requirements. Usually when this happens I have to make several iterations to a model, and the client still does not know exactly what they want.  In addition additional issues can arise when certain stakeholders of a project are not consulted prior to the design or after the project is over because it can cause miss understandings and confusion by the end user as well as possibly not solving the original problem for which a project is intended to solve. One common thread between each type of knowledge is that they can all be avoided through the use of good communication. For example, if a modeler is new to a company then they should ask older employees about any business specific rules that may be documented or undocumented that must be applied to projects in general. Furthermore, if a modeler is not really familiar with a specific data modeling software then they need to speak up and ask for help form other employees or their manager. This will not only help the modeler in the project, but also help them in future projects that they do for the company. Additionally, if a project is not clearly defined prior to a data modeler being assigned the modeling project then it is their responsibility to communicate with the other stakeholders to clarify any part of a project that is unclear so that the data model that is created is accurately aligned with a project.

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  • Modeling a cellphone bill: should I use single-table inheritance or polymorphic associations?

    - by Horace Loeb
    In my domain: Users have many Bills Bills have many BillItems (and therefore Users have many BillItems through Bills) Every BillItem is one of: Call SMS (text message) MMS (multimedia message) Data Here are the properties of each individual BillItem (some are common): My question is whether I should model this arrangement with single-table inheritance (i.e., one "bill_items" table with a "type" column) or polymorphism (separate tables for each BillItem type), and why.

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  • Data Modeling Help - Do I add another table, change existing table's usage, or something else?

    - by StackOverflowNewbie
    Assume I have the following tables and relationships: Person - Id (PK) - Name A Person can have 0 or more pets: Pet - Id (PK) - PersonId (FK) - Name A person can have 0 or more attributes (e.g. age, height, weight): PersonAttribute _ Id (PK) - PersonId (FK) - Name - Value PROBLEM: I need to represent pet attributes, too. As it turns out, these pet attributes are, in most cases, identical to the attributes of a person (e.g. a pet can have an age, height, and weight too). How do I represent pet attributes? Do I create a PetAttribute table? PetAttribute Id (PK) PetId (FK) Name Value Do I change PersonAttribute to GenericAttribute and have 2 foreign keys in it - one connecting to Person, the other connecting to Pet? GenericAttribute Id (PK) PersonId (FK) PetId (FK) Name Value NOTE: if PersonId is set, then PetId is not set. If PetId is set, PersonId is not set. Do something else?

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  • Differences between a conceptual UML class diagram and an ERD?

    - by Adam
    If I create a conceptual class diagram such that each class captures 'name' and 'attributes' but not 'operations', have I not basically created what would be otherwise considered an ERD? I'm trying to gain an understanding of what the differences are between creating a conceptual class diagram as I have described versus calling it a ERD? If these are still two different animals, can somebody please explain what the differences are?

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  • database modeling for google app engine for multiple revison of entity.

    - by iamgopal
    hi, in my application ( kind of wiki clone ) - an article is frequently changing. and i need to track all changes that are done on that article. { text only. } one crude way i have done it, is to add a datetime property and create a new entity everytime something change. which is too much database wasting. { and also un-necessary index waste too. } and also need to re-create parent-child and entity relationships. i also have log which can show changes -- but i want some thing easier , so that jumping from one version to another version could be easier. ideas ? thanks.

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  • Are comonads a good fit for modeling the Wumpus world?

    - by Tim Stewart
    I'm trying to find some practical applications of a comonad and I thought I'd try to see if I could represent the classical Wumpus world as a comonad. I'd like to use this code to allow the Wumpus to move left and right through the world and clean up dirty tiles and avoid pits. It seems that the only comonad function that's useful is extract (to get the current tile) and that moving around and cleaning tiles would not use be able to make use of extend or duplicate. I'm not sure comonads are a good fit but I've seen a talk (Dominic Orchard: A Notation for Comonads) where comonads were used to model a cursor in a two-dimensional matrix. If a comonad is a good way of representing the Wumpus world, could you please show where my code is wrong? If it's wrong, could you please suggest a simple application of comonads? module Wumpus where -- Incomplete model of a world inhabited by a Wumpus who likes a nice -- tidy world but does not like falling in pits. import Control.Comonad -- The Wumpus world is made up of tiles that can be in one of three -- states. data Tile = Clean | Dirty | Pit deriving (Show, Eq) -- The Wumpus world is a one dimensional array partitioned into three -- values: the tiles to the left of the Wumpus, the tile occupied by -- the Wumpus, and the tiles to the right of the Wumpus. data World a = World [a] a [a] deriving (Show, Eq) -- Applies a function to every tile in the world instance Functor World where fmap f (World as b cs) = World (fmap f as) (f b) (fmap f cs) -- The Wumpus world is a Comonad instance Comonad World where -- get the part of the world the Wumpus currently occupies extract (World _ b _) = b -- not sure what this means in the Wumpus world. This type checks -- but does not make sense to me. extend f w@(World as b cs) = World (map world as) (f w) (map world cs) where world v = f (World [] v []) -- returns a world in which the Wumpus has either 1) moved one tile to -- the left or 2) stayed in the same place if the Wumpus could not move -- to the left. moveLeft :: World a -> World a moveLeft w@(World [] _ _) = w moveLeft (World as b cs) = World (init as) (last as) (b:cs) -- returns a world in which the Wumpus has either 1) moved one tile to -- the right or 2) stayed in the same place if the Wumpus could not move -- to the right. moveRight :: World a -> World a moveRight w@(World _ _ []) = w moveRight (World as b cs) = World (as ++ [b]) (head cs) (tail cs) initWorld = World [Dirty, Clean, Dirty] Dirty [Clean, Dirty, Pit] -- cleans the current tile cleanTile :: Tile -> Tile cleanTile Dirty = Clean cleanTile t = t Thanks!

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  • Can UML be used to model a Functional program?

    - by iestyn
    More specifically, how do you model a functional program, or one developed using the Functional Style (without classes) using a diagram, and not textual representation, is it at all possible and could someone please direct me towards the nearest application that would do this (open source, of free as in beer, if you please)

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  • What IDE to use for Python

    - by husayt
    As a Python newbie, it is interesting to know what IDE's ("GUIs/editors") others use for Python coding. If you can just give the name (e.g. Textpad, Eclipse ..) that will be enough. If it is already mentioned, you can just vote for it. But if you can also give some more comparative information, that will be much appreciated. Thanks. Update: Results so far PyDev with Eclipse (CP, F, AC, PD, EM, SI, MLS, UML, SC, UT, LN, CF, BM) Komodo (CP, C/F, MLS, PD, AC, SC, SI, BM, LN, CF, CT) Emacs (CP, F, AC, MLS, PD, EM, SC, SI, BM, LN, CF, CT, UT, UML) Vim (CP, F, AC, MLS, SI, BM, LN, CF ) TextMate (Mac, CT, CF, MLS, SI, BM, LN) Gedit (Linux, F, AC, MLS, BM, LN, CT [sort of]) Idle (CP, F, AC) PIDA (Linux, CP, F, AC, MLS, SI, BM, LN, CF)(VIM Based) NotePad++ (Windows) BlueFish (Linux) JEdit (CP, F, BM, LN, CF, MLS) E-Texteditor (TextMate Clone for Windows) WingIde (CP, C, AC, MLS (support for C), PD, EM, SC, SI, BM, LN, CF, CT, UT) Eric Ide (CP, F, AC, PD, EM, SI, LN, CF, UT) Pyscripter (Windows, F, AC, PD, EM, SI, LN, CT, UT) ConTEXT (Windows, C) SPE (F, AC, UML) SciTE (CP, F, MLS, EM, BM, LN, CF, CT, SH) Zeus (W, C, BM, LN, CF, SI, SC, CT) NetBeans (CP, F, PD, UML, AC, MLS, SC, SI, BM, LN, CF, CT, UT, RAD) DABO (CP) BlackAdder (C, CP, CF, SI) PythonWin (W, F, AC, PD, SI, BM, CF) Geany (CP, F, very limited AC, MLS, SI, BM, LN, CF) UliPad (CP, F, AC, PD, MLS, SI, LI, CT, UT, BM) Boa Constructor (CP, F, AC, PD, EM, SI, BM, LN, UML, CF, CT) ScriptDev (W, C, AC, MLS, PD, EM, SI, BM, LN, CF, CT) Spider (CP, F, AC) Editra (CP, F, AC, MLS, SC, SI, BM, LN, CF) Pfaide (Windows, C, AC, MLS, SI, BM, LN, CF, CT) KDevelop (CP, F, MLS, SC, SI, BM, LN, CF) Acronyms used: CP - Cross Platfom C - Commercial F - Free AC - Automatic Code-completion MLS - Multi-Language Support PD - Integrated Python Debugging EM - ErrorMarkup SC - Source Control integration SI - Smart Indent BM - Bracket Matching LN - Line Numbering UML - UML editing / viewing CF - Code Folding CT - Code Templates UT - Unit Testing UID - Gui Designer (e.g. QT, Eric, ..) DB - integrated database support RAD - Rapid app development support I don't mention basics like Syntax highlighting as I expect these by default. This is a just dry list reflecting your feedback and comments, I am not advocating any of these tools. I will keep updating this list as you keep posting your answers. PS. Can you help me to add features of the above editors to the list (like autocomplete, debugging, or etc)?

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  • Apress Deal of the Day - 17/March/2011

    - by TATWORTH
    v\:* {behavior:url(#default#VML);} o\:* {behavior:url(#default#VML);} w\:* {behavior:url(#default#VML);} .shape {behavior:url(#default#VML);} Normal 0 false false false false EN-GB X-NONE X-NONE MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;} Today’s $10 Deal of the day at http://www.apress.com/info/dailydeal  is  Beginning SQL Server Modeling: Model-Driven Application Development in SQL Server 2008 Get ready for model-driven application development with SQL Server Modeling! This book covers Microsoft's SQL Server Modeling (formerly known under the code name "Oslo") in detail and contains the information you need to be successful with designing and implementing workflow modeling.

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