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  • The Interaction between Three-Tier Client/Server Model and Three-Tier Application Architecture Model

    The three-tier client/server model is a network architectural approach currently used in modern networking. This approach divides a network in to three distinct components. Three-Tier Client/Server Model Components Client Component Server Component Database Component The Client Component of the network typically represents any device on the network. A basic example of this would be computer or another network/web enabled devices that are connected to a network. Network clients request resources on the network, and are usually equipped with a user interface for the presentation of the data returned from the Server Component. This process is done through the use of various software clients, and example of this can be seen through the use of a web browser client. The web browser request information from the Server Component located on the network and then renders the results for the user to process. The Server Components of the network return data based on specific client request back to the requesting client.  Server Components also inherit the attributes of a Client Component in that they are a device on the network and that they can also request information from other Server Components. However what differentiates a Client Component from a Server Component is that a Server Component response to requests from devices on the network. An example of a Server Component can be seen in a web server. A web server listens for new requests and then interprets the request, processes the web pages, and then returns the processed data back to the web browser client so that it may render the data for the user to interpret. The Database Component of the network returns unprocessed data from databases or other resources. This component also inherits attributes from the Server Component in that it is a device on a network, it can request information from other server components and database components, and it also listens for new requests so that it can return data when needed. The three-tier client/server model is very similar to the three-tier application architecture model, and in fact the layers can be mapped to one another. Three-Tier Application Architecture Model Presentation Layer/Logic Business Layer/Logic Data Layer/Logic The Presentation Layer including its underlying logic is very similar to the Client Component of the three-tiered model. The Presentation Layer focuses on interpreting the data returned by the Business Layer as well as presents the data back to the user.  Both the Presentation Layer and the Client Component focus primarily on the user and their experience. This allows for segments of the Business Layer to be distributable and interchangeable because the Presentation Layer is not directly integrated in with Business Layer. The Presentation Layer does not care where the data comes from as long as it is in the proper format. This allows for the Presentation Layer and Business Layer to be stored on one or more different servers so that it can provide a higher availability to clients requesting data. A good example of this is a web site that uses load balancing. When a web site decides to take on the task of load balancing they must obtain a network device that sits in front of a one or machines in order to distribute the request across multiple servers. When a user comes in through the load balanced device they are redirected to a specific server based on a few factors. Common Load Balancing Factors Current Server Availability Current Server Response Time Current Server Priority The Business Layer and corresponding logic are business rules applied to data prior to it being sent to the Presentation Layer. These rules are used to manipulate the data coming from the Data Access Layer, in addition to validating any data prior to being stored in the Data Access Layer. A good example of this would be when a user is trying to create multiple accounts under one email address. The Business Layer logic can prevent duplicate accounts by enforcing a unique email for every new account before the data is even stored in the Data Access Layer. The Server Component can be directly tied to this layer in that the server typically stores and process the Business Layer before it is returned to the end-user via the Presentation Layer. In addition the Server Component can also run automated process through the Business Layer on the data in the Data Access Layer so that additional business analysis can be derived from the data that has been already collected. The Data Layer and its logic are responsible for storing information so that it can be easily retrieved. Typical in most modern applications data is stored in a database management system however data can also be in the form of files stored on a file server. In addition a database can take on one of several forms. Common Database Formats XML File Pipe Delimited File Tab Delimited File Comma Delimited File (CSV) Plain Text File Microsoft Access Microsoft SQL Server MySql Oracle Sybase The Database component of the Networking model can be directly tied to the Data Layer because this is where the Data Layer obtains the data to return back the Business Layer. The Database Component basically allows for a place on the network to store data for future use. This enables applications to save data when they can and then quickly recall the saved data as needed so that the application does not have to worry about storing the data in memory. This prevents overhead that could be created when an application must retain all data in memory. As you can see the Three-Tier Client/Server Networking Model and the Three-Tiered Application Architecture Model rely very heavily on one another to function especially if different aspects of an application are distributed across an entire network. The use of various servers and database servers are wonderful when an application has a need to distribute work across the network. Network Components and Application Layers Interaction Database components will store all data needed for the Data Access Layer to manipulate and return to the Business Layer Server Component executes the Business Layer that manipulates data so that it can be returned to the Presentation Layer Client Component hosts the Presentation Layer that  interprets the data and present it to the user

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  • Custom ASP.Net MVC 2 ModelMetadataProvider for using custom view model attributes

    - by SeanMcAlinden
    There are a number of ways of implementing a pattern for using custom view model attributes, the following is similar to something I’m using at work which works pretty well. The classes I’m going to create are really simple: 1. Abstract base attribute 2. Custom ModelMetadata provider which will derive from the DataAnnotationsModelMetadataProvider   Base Attribute MetadataAttribute using System; using System.Web.Mvc; namespace Mvc2Templates.Attributes {     /// <summary>     /// Base class for custom MetadataAttributes.     /// </summary>     public abstract class MetadataAttribute : Attribute     {         /// <summary>         /// Method for processing custom attribute data.         /// </summary>         /// <param name="modelMetaData">A ModelMetaData instance.</param>         public abstract void Process(ModelMetadata modelMetaData);     } } As you can see, the class simple has one method – Process. Process accepts the ModelMetaData which will allow any derived custom attributes to set properties on the model meta data and add items to its AdditionalValues collection.   Custom Model Metadata Provider For a quick explanation of the Model Metadata and how it fits in to the MVC 2 framework, it is basically a set of properties that are usually set via attributes placed above properties on a view model, for example the ReadOnly and HiddenInput attributes. When EditorForModel, DisplayForModel or any of the other EditorFor/DisplayFor methods are called, the ModelMetadata information is used to determine how to display the properties. All of the information available within the model metadata is also available through ViewData.ModelMetadata. The following class derives from the DataAnnotationsModelMetadataProvider built into the mvc 2 framework. I’ve overridden the CreateMetadata method in order to process any custom attributes that may have been placed above a property in a view model.   CustomModelMetadataProvider using System; using System.Collections.Generic; using System.Linq; using System.Web.Mvc; using Mvc2Templates.Attributes; namespace Mvc2Templates.Providers {     public class CustomModelMetadataProvider : DataAnnotationsModelMetadataProvider     {         protected override ModelMetadata CreateMetadata(             IEnumerable<Attribute> attributes,             Type containerType,             Func<object> modelAccessor,             Type modelType,             string propertyName)         {             var modelMetadata = base.CreateMetadata(attributes, containerType, modelAccessor, modelType, propertyName);               attributes.OfType<MetadataAttribute>().ToList().ForEach(x => x.Process(modelMetadata));               return modelMetadata;         }     } } As you can see, once the model metadata is created through the base method, a check for any attributes deriving from our new abstract base attribute MetadataAttribute is made, the Process method is then called on any existing custom attributes with the model meta data for the property passed in.   Hooking it up The last thing you need to do to hook it up is set the new CustomModelMetadataProvider as the current ModelMetadataProvider, this is done within the Global.asax Application_Start method. Global.asax protected void Application_Start()         {             AreaRegistration.RegisterAllAreas();               RegisterRoutes(RouteTable.Routes);               ModelMetadataProviders.Current = new CustomModelMetadataProvider();         }   In my next post, I’m going to demonstrate a cool custom attribute that turns a textbox into an ajax driven AutoComplete text box. Hope this is useful. Kind Regards, Sean McAlinden.

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  • Backbone.js (model instanceof Model) via Chrome Extension

    - by Leoncelot
    Hey guys, This is my first time ever posting on this site and the problem I'm about to pose is difficult to articulate due to the set of variables required to arrive at it. Let me just quickly explain the framework I'm working with. I'm building a Chrome Extension using jQuery, jQuery-ui, and Backbone The entire JS suite for the extension is written in CoffeeScript and I'm utilizing Rails and the asset pipeline to manage it all. This means that when I want to deploy my extension code I run rake assets:precompile and copy the resulting compressed JS to my extensions Directory. The nice thing about this approach is that I can actually run the extension js from inside my Rails app by including the library. This is basically the same as my extensions background.js file which injects the js as a content script. Anyway, the problem I've recently encountered was when I tried testing my extension on my buddy's site, whiskeynotes.com. What I was noticing is that my backbone models were being mangled upon adding them to their respective collections. So something like this.collection.add(new SomeModel) created some nonsense version of my model. This code eventually runs into Backbone's prepareModel code _prepareModel: function(model, options) { options || (options = {}); if (!(model instanceof Model)) { var attrs = model; options.collection = this; model = new this.model(attrs, options); if (!model._validate(model.attributes, options)) model = false; } else if (!model.collection) { model.collection = this; } return model; }, Now, in most of the sites on which I've tested the extension, the result is normal, however on my buddy's site the !(model instance Model) evaluates to true even though it is actually an instance of the correct class. The consequence is a super messed up version of the model where the model's attributes is a reference to the models collection (strange right?). Needless to say, all kinds of crazy things were happening afterward. Why this is occurring is beyond me. However changing this line (!(model instanceof Model)) to (!(model instanceof Backbone.Model)) seems to fix the problem. I thought maybe it had something to do with the Flot library (jQuery graph library) creating their own version of 'Model' but looking through the source yielded no instances of it. I'm just curious as to why this would happen. And does it make sense to add this little change to the Backbone source? Update: I just realized that the "fix" doesn't actually work. I can also add that my backbone Models are namespaced in a wrapping object so that declaration looks something like class SomeNamespace.SomeModel extends Backbone.Model

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  • Web application / Domain model integration using JSON capable DTOs [on hold]

    - by g-makulik
    I'm a bit confused about architectural choices for the web-applications/java/python world. For c/c++ world the available (open source) choices to implement web applications is pretty limited to zero, involving java or python the choices explode to a,- hard to sort out -, mess of available 'frameworks' and application approaches. I want to sort out a clean MVC model, where the M stands for a fully blown (POCO, POJO driven) domain model (according M.Fowler's EAA pattern) using a mature OO language (Java,C++) for implementation. The background is: I have a system with certain hardware components (that introduce system immanent active behavior) and a configuration database for system meta and HW-components configuration data (these are even usually self contained, since the HW-components are capable to persist their configuration data anyway). For realization of the configuration/status data exchange protocol with the HW-components we have chosen the Google Protobuf format, which works well for the directly wired communication with these components. This protocol is already used successfully with a Java based GUI application via TCP/IP connection to the main system controlling HW-component. This application has some drawbacks and design flaws for historical reasons. Now we want to develop an abstract model (domain model) for configuration and monitoring those HW-components, that represents a more use case oriented view to the overall system behavior. I have the feeling that a plain Java class model would fit best for this (c++ implementation seems to have too much implementation/integration overhead with viable language-bridge interfaces). Google Protobuf message definitions could still serve well to describe DTO objects used to interact with a domain model API. But integrating Google Protobuf messages client side for e.g. data binding in the current view doesn't seem to be a good choice. I'm thinking about some extra serialization features, e.g. for JSON based data exchange with the views/controllers. Most lightweight solutions seem to involve a python based presentation layer using JSON based data transfer (I'm at least not sure to be fully informed about this). Is there some lightweight (applicable for a limited ARM Linux platform) framework available, supporting such architecture to realize a web-application? UPDATE: According to my recent research and comments of colleagues I've noticed that using Java (and some JVM) might not be the preferable choice for integration with python on a limited linux system as we have (running on ARM9 with hard to discuss memory and MCU costs), but C/C++ modules would do well for this (since this forms the native interface to python extensions, doesn't it?). I can imagine to provide a domain model from an appropriate C/C++ API (though I still think it's more efforts and higher skill requirements for the involved developers to do with these languages). Still I'm searching for a good approach that supports such architecture. I'll appreciate any pointers!

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  • Camera not staying behind model while moving in circle

    - by ChocoMan
    I have a camera behind a model (3rd Person) and I'm having problems KEEPING it behind the model. When I first start my game, you see the back of the model. If the model moves forward, backward or strafe left or right, the camera moves along accordingly. When the model rotates (stationary), the camera rotates accordingly with the model still pointing at the model's back. So far, so good. The problem comes when the player is BOTH moving and rotating at the same time. Take for example a model moving in a circular pattern like running around a track. As the model moves in this motion, the model rotates slightly more with each complete rotation. Eventually, instead of looking at the model's back, eventually you will see the model in a profile view and before you know it, the model's front is facing the camera. And when you stop moving the model, the model stays in that position. So, as long as my model is stationary and rotating in one place, the camera rotates correctly. But as soon as there is any sort movement while rotating, the model is offset by a mysterious increasing amount. How can I keep the camera maintaining the same view no matter how I move AND rotate at the same time? // Rotates model and pitches camera on its own axis public void modelRotMovement(GamePadState pController) { /* For rotating the model left or right. * Camera maintains distance from model * throughout rotation and if model moves * to a new position. */ Yaw = pController.ThumbSticks.Right.X * MathHelper.ToRadians(speedAngleMAX); AddRotation = Quaternion.CreateFromAxisAngle(Vector3.Up, yaw); //AddRotation = Quaternion.CreateFromYawPitchRoll(Yaw, 0, 0); ModelLoad.MRotation *= AddRotation; MOrientation = Matrix.CreateFromQuaternion(ModelLoad.MRotation); Pitch = pController.ThumbSticks.Right.Y * MathHelper.ToRadians(speedAngleMAX); AddPitch = Quaternion.CreateFromAxisAngle(Vector3.Up, pitch); ModelLoad.CRotation *= AddPitch; COrientation = Matrix.CreateFromQuaternion(ModelLoad.CRotation); } // Orbit (yaw) Camera around model public void cameraYaw(float yaw) { Vector3 yawAngle = ModelLoad.CameraPos - ModelLoad.camTarget; Vector3 axisYaw = Vector3.Up; ModelLoad.CameraPos = Vector3.Transform(yawAngle, Matrix.CreateFromAxisAngle(axisYaw, yaw)) + ModelLoad.camTarget; }

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  • Move model forward base on model orientation

    - by ChocoMan
    My model rotates on it's own Y-axis regardless of where it is in the world. Here are the controls for the left ThumbStick: UP (move model forward on Z-Axis) DOWN (move model backward on Z-Axis) LEFT & RIGHT (strafe to either side) The problem is adjusting the direction the model's orientation UP and DOWN if the player should also rotate the player while moving forward or backwards. An example what Im trying to achieve would be a car doing donuts. The car is always facing the current direction that it interprets as forward (or rear as backwards) in relation to it's local rotation. Here is how Im calling the movement: // Rotate model with Right Thumbstick along X-Axis modelRotation -= pController.ThumbSticks.Right.X * mRotSpeed; // Move Forward if (pController.IsButtonDown(Buttons.LeftThumbstickUp)) { modelPosition.Z -= -pController.ThumbSticks.Left.Y * speed; } // Move Backward if (pController.IsButtonDown(Buttons.LeftThumbstickDown)) { modelPosition.Z += pController.ThumbSticks.Left.Y * speed; } // Strafe Left if (pController.IsButtonDown(Buttons.LeftThumbstickLeft)) { modelPosition.X += -pController.ThumbSticks.Left.X * speed; } // Strafe Right if (pController.IsButtonDown(Buttons.LeftThumbstickRight)) { modelPosition.X -= pController.ThumbSticks.Left.X * speed; } // DeadZone if (!pController.IsButtonDown(Buttons.LeftThumbstickUp) && !pController.IsButtonDown(Buttons.LeftThumbstickDown) && !pController.IsButtonDown(Buttons.LeftThumbstickLeft) && !pController.IsButtonDown(Buttons.LeftThumbstickRight)) { }

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  • How to remove a model object from an EMF model and its GEF Editor via Adapter

    - by s.d
    This question is principally a follow-up to my question about EMF listening mechanisms. So, I have a third-party EMF model (uneditable) which is based on a generic graph model. The structure is as follows: Project | ItemGraph | Item | Document | DocumentGraph / | \ Tokens Nodes Relations(Edges) I have a GEF editor which works on the DocumentGraph (i.e., not the root object, perhaps this is a problem?): getGraphicalViewer().setContents(documentGraph). THe editor has the following edit part structure: DocumentGraphEP / \ Primary Connection LayerEP LayerEP / \ | TokenEP NodeEP RelationEP PrimaryLayerEP and ConnectionLayerEP both have simple Strings as model, which are not represented in the EMF (domain) model. They are simply used to add a primary (i.e., node) layer, and a connection layer (with ShortestPathConnectionRouter) to the editor. Problem: I am trying to get myself into the workings of EMF adapters, and have tried to make use of the available tutorials, mainly the EMF-GEF Eclipse tutorial, vainolo's blog, and vogella's tutorial. I thought I'd start with an easy thing, so tried to remove a node from the graph and see if I get it to work. Which I didn't, and I don't see where the problem is. I can select a node, and have the generic delete Action in my toolbar, but when I click it, nothing happens. Here is the respective source code for the different responsible parts. Please be so kind to point me to any errors (of thinking, coding errors, whathaveyou) you can find. NodeEditPart public class NodeEditPart extends AbstractGraphicalEditPart implements Adapter { protected IFigure createFigure() { return new NodeFigure(); } protected void createEditPolicies() { .... installEditPolicy(EditPolicy.COMPONENT_ROLE, new NodeComponentEditPolicy()); } protected void refreshVisuals() { NodeFigure figure = (NodeFigure) getFigure(); SNode model = (SNode) getModel(); PrimaryLayerEditPart parent = (PrimaryLayerEditPart) getParent(); // Set text figure.getLabel().setText(model.getSName()); .... } public void activate() { if (isActive()) return; // start listening for changes in the model ((Notifier)getModel()).eAdapters().add(this); super.activate(); } public void deactivate() { if (!isActive()) return; // stop listening for changes in the model ((Notifier)getModel()).eAdapters().remove(this); super.deactivate(); } private Notifier getSDocumentGraph() { return ((SNode)getModel()).getSDocumentGraph(); } @Override public void notifyChanged(Notification notification) { int type = notification.getEventType(); switch( type ) { case Notification.ADD: case Notification.ADD_MANY: case Notification.REMOVE: case Notification.REMOVE_MANY: refreshChildren(); break; case Notification.SET: refreshVisuals(); break; } } @Override public Notifier getTarget() { return target; } @Override public void setTarget(Notifier newTarget) { this.target = newTarget; } @Override public boolean isAdapterForType(Object type) { return type.equals(getModel().getClass()); } } NodeComponentEditPolicy public class NodeComponentEditPolicy extends ComponentEditPolicy { public NodeComponentEditPolicy() { super(); } protected Command createDeleteCommand(GroupRequest deleteRequest) { DeleteNodeCommand cmd = new DeleteNodeCommand(); cmd.setSNode((SNode) getHost().getModel()); return cmd; } } DeleteNodeCommand public class DeleteNodeCommand extends Command { private SNode node; private SDocumentGraph graph; @Override public void execute() { node.setSDocumentGraph(null); } @Override public void undo() { node.setSDocumentGraph(graph); } public void setSNode(SNode node) { this.node = node; this.graph = node.getSDocumentGraph(); } } All seems to work fine: When a node is selected in the editor, the delete symbol is activated in the toolbar, but when it is clicked, nothing happens in the editor. I'd be very thankful for any pointers :).

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  • Camera wont stay behind model after pitch, then rotation

    - by ChocoMan
    I have a camera position behind a model. Currently, if I push the left thumbstick making my model move forward, backward, or strafe, the camera stays with the model. If I push the right thumbstick left or right, the model rotates in those directions fine along with the camera rotating while maintaining its position relatively behind the model. But when I pitch the model up or down, then rotate the model afterwards, the camera moves slightly rotates in a clock-like fashion behind the model. If I do a few rotations of the model and try to pitch the camera, the camera will eventually be looking at the side, then eventually the front of the model while also rotating in a clock-like fashion. My question is, how do I keep the camera to pitch up and down behind the model no matter how much the model has rotated? Here is what I got: // Rotates model and pitches camera on its own axis public void modelRotMovement(GamePadState pController) { // Rotates Camera with model Yaw = pController.ThumbSticks.Right.X * MathHelper.ToRadians(angularSpeed); // Pitches Camera around model Pitch = pController.ThumbSticks.Right.Y * MathHelper.ToRadians(angularSpeed); AddRotation = Quaternion.CreateFromYawPitchRoll(Yaw, 0, 0); ModelLoad.MRotation *= AddRotation; MOrientation = Matrix.CreateFromQuaternion(ModelLoad.MRotation); } // Orbit (yaw) Camera around with model (only seeing back of model) public void cameraYaw(Vector3 axisYaw, float yaw) { ModelLoad.CameraPos = Vector3.Transform(ModelLoad.CameraPos - ModelLoad.camTarget, Matrix.CreateFromAxisAngle(axisYaw, yaw)) + ModelLoad.camTarget; } // Raise camera above or below model's shoulders public void cameraPitch(Vector3 axisPitch, float pitch) { ModelLoad.CameraPos = Vector3.Transform(ModelLoad.CameraPos - ModelLoad.camTarget, Matrix.CreateFromAxisAngle(axisPitch, pitch)) + ModelLoad.camTarget; } // Call in update method public void updateCamera() { cameraYaw(Vector3.Up, Yaw); cameraPitch(Vector3.Right, Pitch); } NOTE: I tried to use addPitch just like addRotation but it didn't work...

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  • Rails - Accessing model class methods from within ActiveRecord model

    - by aaronrussell
    I have a simple standalone model that doesn't inherit from ActiveRecord or anything else, called SmsSender. As the name suggests, it delivers text messages to an SMS gateway. I also have an ActiveRecord model called SmsMessage which has an instance method called deliver: def deliver SmsSender.deliver_message(self) self.update_attributes :status => "Sent" end The above is returning uninitialized constant SmsSender. I'm sure this is dead simple, but how can I access the SmsSender class from within my model?

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  • Database model for keeping track of likes/shares/comments on blog posts over time

    - by gage
    My goal is to keep track of the popular posts on different blog sites based on social network activity at any given time. The goal is not to simply get the most popular now, but instead find posts that are popular compared to other posts on the same blog. For example, I follow a tech blog, a sports blog, and a gossip blog. The tech blog gets waaay more readership than the other two blogs, so in raw numbers every post on the tech blog will always out number views on the other two. So lets say the average tech blog post gets 500 facebook likes and the other two get an average of 50 likes per post. Then when there is a sports blog post that has 200 fb likes and a gossip blog post with 300 while the tech blog posts today have 500 likes I want to highlight the sports and gossip blog posts (more likes than average vs tech blog with more # of likes but just average for the blog) The approach I am thinking of taking is to make an entry in a database for each blog post. Every x minutes (say every 15 minutes) I will check how many likes/shares/comments an entry has received on all the social networks (facebook, twitter, google+, linkeIn). So over time there will be a history of likes for each blog post, i.e post 1234 after 15 min: 10 fb likes, 4 tweets, 6 g+ after 30 min: 15 fb likes, 15 tweets, 10 g+ ... ... after 48 hours: 200 fb likes, 25 tweets, 15 g+ By keeping a history like this for each blog post I can know the average number of likes/shares/tweets at any give time interval. So for example the average number of fb likes for all blog posts 48hrs after posting is 50, and a particular post has 200 I can mark that as a popular post and feature/highlight it. A consideration in the design is to be able to easily query the values (likes/shares) for a specific time-frame, i.e. fb likes after 30min or tweets after 24 hrs in-order to compute averages with which to compare against (or should averages be stored in it's own table?) If this approach is flawed or could use improvement please let me know, but it is not my main question. My main question is what should a database scheme for storing this info look like? Assuming that the above approach is taken I am trying to figure out what a database schema for storing the likes over time would look like. I am brand new to databases, in doing some basic reading I see that it is advisable to make a 3NF database. I have come up with the following possible schema. Schema 1 DB Popular Posts Table: Post post_id ( primary key(pk) ) url title Table: Social Activity activity_id (pk) url (fk) type (i.e. facebook,twitter,g+) value timestamp This was my initial instinct (base on my very limited db knowledge). As far as I under stand this schema would be 3NF? I searched for designs of similar database model, and found this question on stackoverflow, http://stackoverflow.com/questions/11216080/data-structure-for-storing-height-and-weight-etc-over-time-for-multiple-users . The scenario in that question is similar (recording weight/height of users overtime). Taking the accepted answer for that question and applying it to my model results in something like: Schema 2 (same as above, but break down the social activity into 2 tables) DB Popular Posts Table: Post post_id (pk) url title Table: Social Measurement measurement_id (pk) post_id (fk) timestamp Table: Social stat stat_id (pk) measurement_id (fk) type (i.e. facebook,twitter,g+) value The advantage I see in schema 2 is that I will likely want to access all the values for a given time, i.e. when making a measurement at 30min after a post is published I will simultaneous check number of fb likes, fb shares, fb comments, tweets, g+, linkedIn. So with this schema it may be easier get get all stats for a measurement_id corresponding to a certain time, i.e. all social stats for post 1234 at time x. Another thought I had is since it doesn't make sense to compare number of fb likes with number of tweets or g+ shares, maybe it makes sense to separate each social measurement into it's own table? Schema 3 DB Popular Posts Table: Post post_id (pk) url title Table: fb_likes fb_like_id (pk) post_id (fk) timestamp value Table: fb_shares fb_shares_id (pk) post_id (fk) timestamp value Table: tweets tweets__id (pk) post_id (fk) timestamp value Table: google_plus google_plus_id (pk) post_id (fk) timestamp value As you can see I am generally lost/unsure of what approach to take. I'm sure this typical type of database problem (storing measurements overtime, i.e temperature statistic) that must have a common solution. Is there a design pattern/model for this, does it have a name? I tried searching for "database periodic data collection" or "database measurements over time" but didn't find anything specific. What would be an appropriate model to solve the needs of this problem?

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  • I don't get object-oriented programming

    - by Joel J. Adamson
    Note: this question is an edited excerpt from a blog posting I wrote a few months ago. After placing a link to the blog in a comment on Programmers.SE someone requested that I post a question here so that they could answer it. This posting is my most popular, as people seem to type "I don't get object-oriented programming" into Google a lot. Feel free to answer here, or in a comment at Wordpress. What is object-oriented programming? No one has given me a satisfactory answer. I feel like you will not get a good definition from someone who goes around saying “object” and “object-oriented” with his nose in the air. Nor will you get a good definition from someone who has done nothing but object-oriented programming. No one who understands both procedural and object-oriented programming has ever given me a consistent idea of what an object-oriented program actually does. Can someone please give me their ideas of the advantages of object-oriented programming?

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  • I don't get object-oriented programming

    - by Joel J. Adamson
    Note: this question is an edited excerpt from a blog posting I wrote a few months ago. After placing a link to the blog in a comment on Programmers.SE someone requested that I post a question here so that they could answer it. This posting is my most popular, as people seem to type "I don't get object-oriented programming" into Google a lot. Feel free to answer here, or in a comment at Wordpress. What is object-oriented programming? No one has given me a satisfactory answer. I feel like you will not get a good definition from someone who goes around saying “object” and “object-oriented” with his nose in the air. Nor will you get a good definition from someone who has done nothing but object-oriented programming. No one who understands both procedural and object-oriented programming has ever given me a consistent idea of what an object-oriented program actually does. Can someone please give me their ideas of the advantages of object-oriented programming?

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  • Problem with AssetManager while loading a Model type

    - by user1204548
    Today I've tried the AssetManager for the first time with .g3db files and I'm having some problems. Exception in thread "LWJGL Application" com.badlogic.gdx.utils.GdxRuntimeException: com.badlogic.gdx.utils.GdxRuntimeException: Couldn't load dependencies of asset: data/data at com.badlogic.gdx.assets.AssetManager.handleTaskError(AssetManager.java:508) at com.badlogic.gdx.assets.AssetManager.update(AssetManager.java:342) at com.lostchg.martagdx3d.MartaGame.render(MartaGame.java:78) at com.badlogic.gdx.Game.render(Game.java:46) at com.badlogic.gdx.backends.lwjgl.LwjglApplication.mainLoop(LwjglApplication.java:207) at com.badlogic.gdx.backends.lwjgl.LwjglApplication$1.run(LwjglApplication.java:114) Caused by: com.badlogic.gdx.utils.GdxRuntimeException: Couldn't load dependencies of asset: data/data at com.badlogic.gdx.assets.AssetLoadingTask.handleAsyncLoader(AssetLoadingTask.java:119) at com.badlogic.gdx.assets.AssetLoadingTask.update(AssetLoadingTask.java:89) at com.badlogic.gdx.assets.AssetManager.updateTask(AssetManager.java:445) at com.badlogic.gdx.assets.AssetManager.update(AssetManager.java:340) ... 4 more Caused by: com.badlogic.gdx.utils.GdxRuntimeException: com.badlogic.gdx.utils.GdxRuntimeException: Couldn't load file: data/data at com.badlogic.gdx.utils.async.AsyncResult.get(AsyncResult.java:31) at com.badlogic.gdx.assets.AssetLoadingTask.handleAsyncLoader(AssetLoadingTask.java:117) ... 7 more Caused by: com.badlogic.gdx.utils.GdxRuntimeException: Couldn't load file: data/data at com.badlogic.gdx.graphics.Pixmap.<init>(Pixmap.java:140) at com.badlogic.gdx.assets.loaders.TextureLoader.loadAsync(TextureLoader.java:72) at com.badlogic.gdx.assets.loaders.TextureLoader.loadAsync(TextureLoader.java:41) at com.badlogic.gdx.assets.AssetLoadingTask.call(AssetLoadingTask.java:69) at com.badlogic.gdx.assets.AssetLoadingTask.call(AssetLoadingTask.java:34) at com.badlogic.gdx.utils.async.AsyncExecutor$2.call(AsyncExecutor.java:49) at java.util.concurrent.FutureTask.run(Unknown Source) at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source) at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source) at java.lang.Thread.run(Unknown Source) Caused by: com.badlogic.gdx.utils.GdxRuntimeException: File not found: data\data (Internal) at com.badlogic.gdx.files.FileHandle.read(FileHandle.java:132) at com.badlogic.gdx.files.FileHandle.length(FileHandle.java:586) at com.badlogic.gdx.files.FileHandle.readBytes(FileHandle.java:220) at com.badlogic.gdx.graphics.Pixmap.<init>(Pixmap.java:137) ... 9 more Why it tries to load that unexisting file? It seems that the AssetManager manages to load my .g3db file at first, because earlier the java console threw some errors related to the textures associated to the 3D scene having to be a power of 2. Relevant code: public void show() { ... assets = new AssetManager(); assets.load("data/levelprueba2.g3db", Model.class); loading = true; ... } private void doneLoading() { Model model = assets.get("data/levelprueba2.g3db", Model.class); for (int i = 0; i < model.nodes.size; i++) { String id = model.nodes.get(i).id; ModelInstance instance = new ModelInstance(model, id); Node node = instance.getNode(id); instance.transform.set(node.globalTransform); node.translation.set(0,0,0); node.scale.set(1,1,1); node.rotation.idt(); instance.calculateTransforms(); instances.add(instance); } loading = false; } public void render(float delta) { super.render(delta); if (loading && assets.update()) doneLoading(); ... } The error points to the line with the assets.update() method. Please, help! Sorry for my bad English and my amateurish doubts.

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  • DDD Model Design and Repository Persistence Performance Considerations

    - by agarhy
    So I have been reading about DDD for some time and trying to figure out the best approach on several issues. I tend to agree that I should design my model in a persistent agnostic manner. And that repositories should load and persist my models in valid states. But are these approaches realistic practically? I mean its normal for a model to hold a reference to a collection of another type. Persisting that model should mean persist the entire collection. Fine. But do I really need to load the entire collection every time I load the model? Probably not. So I can have specialized repositories. Some that load maybe a subset of the object graph via DTOs and others that load the entire object graph. But when do I use which? If I have DTOs, what's stopping client code from directly calling them and completely bypassing the model? I can have mappers and factories to create my models from DTOs maybe? But depending on the design of my models that might not always work. Or it might not allow my models to be created in a valid state. What's the correct approach here?

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  • Keeping game model and graphics/animation separate but in sync

    - by AJM
    Suppose I'm building a chess game where I want to have animations. Pieces glide to their new squares when moved. Pieces perform attack animations when capturing other pieces. I'm not sure how to effectively separate the data and logic needed for these animations and the actual game model (in the MVC sense). The pieces themselves should ideally not have to worry about their pixel coordinates or current animation frame. At the same time, many changes to the model are effectively driven by animations. A moved piece changes its position after (before?) its sprite is done gliding. A piece is removed from the board after the capturing piece is finished its attack animation. How would you suggest I manage the game model, the graphics and animations, and their relationships? For example, where would the animations "live"? How would animations be created and managed in response to player moves? How would animations drive updates to the game model, or how would the game model drive animations?

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  • How can I attach a model to the bone of another model?

    - by kaykayman
    I am trying to attach one animated model to one of the bones of another animated model in an XNA game. I've found a few questions/forum posts/articles online which explain how to attach a weapon model to the bone of another model (which is analogous to what I'm trying to achieve), but they don't seem to work for me. So as an example: I want to attach Model A to a specific bone in Model B. Question 1. As I understand it, I need to calculate the transforms which are applied to the bone on Model B and apply these same transforms to every bone in Model A. Is this right? Question 2. This is my code for calculating the Transforms on a specific bone. private Matrix GetTransformPaths(ModelBone bone) { Matrix result = Matrix.Identity; while (bone != null) { result = result * bone.Transform; bone = bone.Parent; } return result; } The maths of Matrices is almost entirely lost on me, but my understanding is that the above will work its way up the bone structure to the root bone and my end result will be the transform of the original bone relative to the model. Is this right? Question 3. Assuming that this is correct I then expect that I should either apply this to each bone in Model A, or in my Draw() method: private void DrawModel(SceneModel model, GameTime gametime) { foreach (var component in model.Components) { Matrix[] transforms = new Matrix[component.Model.Bones.Count]; component.Model.CopyAbsoluteBoneTransformsTo(transforms); Matrix parenttransform = Matrix.Identity; if (!string.IsNullOrEmpty(component.ParentBone)) parenttransform = GetTransformPaths(model.GetBone(component.ParentBone)); component.Player.Update(gametime.ElapsedGameTime, true, Matrix.Identity); Matrix[] bones = component.Player.GetSkinTransforms(); foreach (SkinnedEffect effect in mesh.Effects) { effect.SetBoneTransforms(bones); effect.EnableDefaultLighting(); effect.World = transforms[mesh.ParentBone.Index] * Matrix.CreateRotationY(MathHelper.ToRadians(model.Angle)) * Matrix.CreateTranslation(model.Position) * parenttransform; effect.View = getView(); effect.Projection = getProjection(); effect.Alpha = model.Opacity; } } mesh.Draw(); } I feel as though I have tried every conceivable way of incorporating the parenttransform value into the draw method. The above is my most recent attempt. Is what I'm trying to do correct? And if so, is there a reason it doesn't work? The above Draw method seems to transpose the models x/z position - but even at these wrong positions, they do not account for the animation of Model B at all. Note: As will be evident from the code my "model" is comprised of a list of "components". It is these "components" that correspond to a single "Microsoft.Xna.Framework.Graphics.Model"

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  • Subscribe/Publish Model in Web-based Application (c#) - Best Practices for Event Handlers

    - by KingOfHypocrites
    I was recently exposed to a desktop application that uses an publish/subscribe model to handle commands, events, etc. I can't seem to find any good examples of using this in a web application, so I wonder if I am off base in trying to use this for web based development (on the server side)? I'm using asp.net c#. My main question in regards to the design is: When using a publish/subscribe model, is it better to have generic commands/events that pass no parameters and then have the subscribers look at static context objects that contain the data relevant to the event? Or is it better to create custom arguments for every event that contain data related to the event? The whole concept of a global container seems so convenient but at the same time seems to break encapsulation. Any thoughts or best practices from anyone who has implemented this type of model in a web based application? Even suggestions on this model out of the scope of my question are appreciated.

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  • Relational Database pioneer Chris Date is giving a seminar 13th/14th May Edinburgh on "SQL and Relat

    - by tonyrogerson
    One of the pioneers of the Relational Database, Chris Date is giving a 2 day seminar in Edinburgh (13th and 14th May 2010) based around his new book "SQL and Relational Theory - How to Write Accurate SQL Code" which if you don't already have I'd say is a must buy. When I first saw this and what he will cover I thought, oh yer - this is going to cost the earth, well it doesn't - its £750 for the two days and there are discounts available for multiple bookings, being a member...(read more)

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  • Recommended Model Based Testing Tools

    - by ModelTester
    Does anyone have any suggestions on what Model Based Testing Tools to use? Is Spec Explorer/SPEC# worth it's weight in tester training? What I have traditionally done is create a Visio Model where I call out the states and associated variables, outputs and expected results from each state. Then in a completely disconnected way, I data drive my test scripts with those variables based on that model. But, they are not connected. I want a way to create a model, associate the variables in a business friendly way, that will then build the data parameters for the scripts. I can't be the first person to need this. Is there a tool out there that will do basically that? Short of developing it myself.

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  • "[object Object]" passed instead of the actual object as parameter

    - by Andrew Latham
    I am using Heroku with a Ruby on Rails application, and running from Safari. I have the following Ajax call: $.ajax({ type : 'POST', url : '/test_page', data : {stuff: arr1}, dataType : 'script' }); arr1 is supposed to be an array of objects. There's a console.log right before that, and it is: [Object, Object, Object, Object, Object, ...] However, I got an error on the server side when I made this ajax call. The logs showed 2012-10-01T03:13:34+00:00 app[web.1]: Parameters: {"stuff"=>"[object Object]"} 2012-10-01T03:13:34+00:00 app[web.1]: WARNING: Can't verify CSRF token authenticity 2012-10-01T03:13:34+00:00 app[web.1]: NoMethodError (undefined method `to_hash' for "[object Object]":String): 2012-10-01T03:13:34+00:00 app[web.1]: Completed 500 Internal Server Error in 1ms I'm unable to replicate the error. It's really confusing to me - what would cause that string to sometimes be passed to the server instead of the object?

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  • SQL SERVER – Creating All New Database with Full Recovery Model

    - by pinaldave
    Sometimes, complex problems have very simple solutions. Let us see the following email which I received recently. “Hi Pinal, In our system when we create new database, by default, they are all created with the Simple Recovery Model. We have to manually change the recovery model after we create the database. We used the following simple T-SQL code: CREATE DATABASE dbname. We are very frustrated with this situation. We want all our databases to have the Full Recovery Model option by default. We are considering the following methods; please suggest the most efficient one among them. 1) Creating a Policy; when it is violated, the database model can be fixed 2) Triggers at Server Level 3) Automated Job which goes through all the databases and checks their recovery model; if the DBA has not changed the model, then the job will list the Databases and change their recovery model Also, we have a situation where we need a database in the Simple Recovery Model as well – how to white list them? Please suggest the best method.” Indeed, an interesting email! The answer to their question, i.e., which is the best method to fit their needs (white list, default, etc)? It will be NONE of the above. Here is the solution in one line and also the easiest way: Just go to your Model database: Path in SSMS >> Databases > System Databases >> model >> Right Click Properties >> Options >> Recovery Model - Select Full from dropdown. Every newly created database takes its base template from the Model Database. If you create a custom SP in the Model Database, when you create a new database, it will automatically exist in that database. Any database that was already created before making changes in the Model Database will not be affected at all. Creating Policy is also a good method, and I will blog about this in a separate blog post, but looking at current specifications of the reader, I think the Model Database should be modified to have a Full Recovery Option. While writing this blog post, I remembered my another blog post where the model database log file was growing drastically even though there were no transactions SQL SERVER – Log File Growing for Model Database – model Database Log File Grew Too Big. NOTE: Please do not touch the Model Database unnecessary. It is a strict “No.” If you want to create an object that you need in all the databases, then instead of creating it in model database, I suggest that you create a new database called maintenance and create the object there. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: PostADay, Readers Question, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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  • Anemic Domain Model, Business Logic and DataMapper (PHP)

    - by sunwukung
    I've implemented a rudimentary ORM layer based on DataMapper (I don't want to use a full blown ORM like Propel/Doctrine - for anything beyond simple fetch/save ops I prefer to access the data directly layer using a SQL abstraction layer). Following the DataMapper pattern, I've endeavoured to keep all persistence operations in the Mapper - including the location of related entities. My Entities have access to their Mapper, although I try not to call Mapper logic from the Entity interface (although this would be simple enough). The result is: // get a mapper and produce an entity $ProductMapper = $di->get('product_mapper'); $Product = $ProductMapper->find('[email protected]','email'); //.. mutaute some values.. save $ProductMapper->save($Product) // uses __get to trigger relation acquisition $Manufacturer = $Product->manufacturer; I've read some articles regarding the concept of an Anemic Domain model, i.e. a Model that does not contain any "business logic". When demonstrating the sort of business logic ideally suited to a Domain Model, however, acquiring related data items is a common example. Therefore I wanted to ask this question: Is persistence logic appropriate in Domain Model objects?

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  • Using an actor model versus a producer-consumer model?

    - by hewhocutsdown
    I'm doing some early-stage research towards architecting a new software application. Concurrency and multithreading will likely play a significant part, so I've been reading up on the various topics. The producer-consumer model, at least how it is expressed in Java, has some surface similarities but appears to be deeply dissimilar to the actor model in use with languages such as Erlang and Scala. I'm having trouble finding any good comparative data, or specific reasons to use or avoid the one or the other. Is the actor model even possible with Java or C#, or do you have do use one of the languages built for the purpose? Is there a third way?

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