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• SQLAuthority News – 2 Whitepapers Announced – AlwaysOn Architecture Guide: Building a High Availability and Disaster Recovery Solution

  - by pinaldave

  Understanding AlwaysOn Architecture is extremely important when building a solution with failover clusters and availability groups. Microsoft has just released two very important white papers related to this subject. Both the white papers are written by top experts in industry and have been reviewed by excellent panel of experts. Every time I talk with various organizations who are adopting the SQL Server 2012 they are always excited with the concept of the new feature AlwaysOn. One of the requests I often here is the related to detailed documentations which can help enterprises to build a robust high availability and disaster recovery solution. I believe following two white paper now satisfies the request. AlwaysOn Architecture Guide: Building a High Availability and Disaster Recovery Solution by Using AlwaysOn Availability Groups SQL Server 2012 AlwaysOn Availability Groups provides a unified high availability and disaster recovery (HADR) solution. This paper details the key topology requirements of this specific design pattern on important concepts like quorum configuration considerations, steps required to build the environment, and a workflow that shows how to handle a disaster recovery. AlwaysOn Architecture Guide: Building a High Availability and Disaster Recovery Solution by Using Failover Cluster Instances and Availability Groups SQL Server 2012 AlwaysOn Failover Cluster Instances (FCI) and AlwaysOn Availability Groups provide a comprehensive high availability and disaster recovery solution. This paper details the key topology requirements of this specific design pattern on important concepts like asymmetric storage considerations, quorum model selection, quorum votes, steps required to build the environment, and a workflow. If you are not going to implement AlwaysOn feature, this two Whitepapers are still a great reference material to review as it will give you complete idea regarding what it takes to implement AlwaysOn architecture and what kind of efforts needed. One should at least bookmark above two white papers for future reference. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Documentation, SQL Download, SQL Query, SQL Server, SQL Tips and Tricks, SQL White Papers, T SQL, Technology Tagged: AlwaysOn

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• Podcast Show Notes: By Any Other Name: Governance and Architecture

  - by Bob Rhubart

  The OTN ArchBeat Podcast returns from a brief summer hiatus with a three-part conversation about IT architecture and governance. My guests for this conversation are Eric Stephens , an Oracle Enterprise architect and a frequent guest on this program. Joining Eric on the panel is Tim Hall , Senior Director of product management for the Oracle Enterprise Repository, Oracle Service Registry, and Oracle Application Integration Architecture. Tim made his first appearance on ArchBeat as panelist on the recent program featuring Thomas Erl. The Conversation Listen to Part 1:Why it's important to revive the dormant conversation about IT governance. Listen to Part 2 (Sept 19): Balancing functional, technical, operational requirements to meet the challenge of defining appropriate governance "guardrails." Listen to Part 3 (Sept 26): Bringing IT architecture out of the ivory tower to make governance a less intimidating, more collaborative process. Additional Resources Leveraging Governance to Sustain Enterprise Architecture Efforts, an Oracle white paper by Eric Stephens. SOA, Cloud, and Service Technologies, a transcript of an ArchBeat interview with Thomas Erl, Tim Hall, and Demed L'Her, in which Tim says the following about governance: "For a long time people have argued that SOA governance is sort of an awkward name, no one wanted to be audited. There's 50% of the world that think, yes, we're going to have to tops down initiative to address this and there's 50% of the world that says that it feels like a heavy weight process that I want no part of. So what I think we should do is change the name…"

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• A Great Work : ADF Architecture TV

  - by mustafakaya

  I would like to information about Oracle ADF Product Management's great work ; ADF Architecture TV. This channel has various subjects such as before start a new ADF or any software project what will you need or how can you select team member's skills, or how to implement and design an ADF projects etc. When developing with a new technology, one of the challenges for technical staff is to both learn the features of the technology and how to implement them, and also consider the broader concepts of design, engineering and architecture. Many an IT project has come undone because IT staff have been focused on the nitty gritty details of writing software, rather than looking at the "bigger picture" of how it will all go together. Oracle's "ADF Architecture TV" plans to address this issue by focusing on architectural issues and developer guidelines for writing ADF software solutions. The goal, to give ADF developers an understanding of the decisions you need to build a successful ADF application, potential architectural blueprints to choose from when putting the ADF application together, and potential best practices to take back to your development team.  You can click here for ADF Architecture TV. 

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• Obj-C component-based game architecture and message forwarding

  - by WanderWeird

  Hello, I've been trying to implement a simple component-based game object architecture using Objective-C, much along the lines of the article 'Evolve Your Hierarchy' by Mick West. To this end, I've successfully used a some ideas as outlined in the article 'Objective-C Message Forwarding' by Mike Ash, that is to say using the -(id)forwardingTargetForSelector: method. The basic setup is I have a container GameObject class, that contains three instances of component classes as instance variables: GCPositioning, GCRigidBody, and GCRendering. The -(id)forwardingTargetForSelector: method returns whichever component will respond to the relevant selector, determined using the -(BOOL)respondsToSelector: method. All this, in a way, works like a charm: I can call a method on the GameObject instance of which the implementation is found in one of the components, and it works. Of course, the problem is that the compiler gives 'may not respond to ...' warnings for each call. Now, my question is, how do I avoid this? And specifically regarding the fact that the point is that each instance of GameObject will have a different set of components? Maybe a way to register methods with the container objects, on a object per object basis? Such as, can I create some kind of -(void)registerMethodWithGameObject: method, and how would I do that? Now, it may or may not be obvious that I'm fairly new to Cocoa and Objective-C, and just horsing around, basically, and this whole thing may be very alien here. Of course, though I would very much like to know of a solution to my specific issue, anyone who would care to explain a more elegant way of doing this would additionally be very welcome. Much appreciated, -Bastiaan

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• P6 Architecture - Register renaming aside, does the limited user registers result in more ops spent

  - by mrjoltcola

  I'm studying JIT design with regard to dynamic languages VM implementation. I haven't done much Assembly since the 8086/8088 days, just a little here or there, so be nice if I'm out of sorts. As I understand it, the x86 (IA-32) architecture still has the same basic limited register set today that it always did, but the internal register count has grown tremendously, but these internal registers are not generally available and are used with register renaming to achieve parallel pipelining of code that otherwise could not be parallelizable. I understand this optimization pretty well, but my feeling is, while these optimizations help in overall throughput and for parallel algorithms, the limited register set we are still stuck with results in more register spilling overhead such that if x86 had double, or quadruple the registers available to us, there may be significantly less push/pop opcodes in a typical instruction stream? Or are there other processor optmizations that also optimize this away that I am unaware of? Basically if I've a unit of code that has 4 registers to work with for integer work, but my unit has a dozen variables, I've got potentially a push/pop for every 2 or so instructions. Any references to studies, or better yet, personal experiences?

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• General N-Tier Architecture Question

  - by whatispunk

  In an N-Tier app you're supposed to have a business logic layer and a data access layer. Is it bad to simply have two assemblies: BusinessLogicLayer.dll and DataAccessLayer.dll to handle all this logic? How do you actually represent these layers. It seems silly, the way I've seen it, to have a BusinessLogic class library containing classes like: CustomerBusinessLogic.cs, OrderBusinessLogic.cs, etc. each calling their appropriately named cousin in the DataAccessLayer class library, i.e. CustomerDataAccess.cs, OrderDataAccess.cs. I want to create a web app using MVP and it doesn't seem so cut and dry as this. There are lots of opinions about where the business logic is supposed to be put in MVP and I'm not sure I've found a really great answer yet. I want this project to be easily testable, and I am trying to adhere to TDD methodologies as best I can. I intend to use MSTest and Rhino Mocks for testing. I was thinking of something like the following for my architecture: I'd use LINQ-To-SQL to talk to the database. WCF services to define data contract interfaces for the business logic layer. Then use MVP with ASP.NET Forms for the UI/BLL. Now, this isn't the start of this project, most of the LINQ stuff is already done, so its stuck. The WCF service would replace the existing DataAccessLayer assembly and the UI/BLL would replace the BusinessLogicLayer assembly etc. This sort of makes sense in my head, but its getting really late. Anyone that's traveled down this path have any guidance? Good links? Warnings? Thanks!

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• change custom mapping - sharp architecture/ fluent nhibernate

  - by csetzkorn

  I am using the sharp architecture which also deploys FNH. The db schema sql code is generated during the testing like this: [TestFixture] [Category("DB Tests")] public class MappingIntegrationTests { [SetUp] public virtual void SetUp() { string[] mappingAssemblies = RepositoryTestsHelper.GetMappingAssemblies(); configuration = NHibernateSession.Init( new SimpleSessionStorage(), mappingAssemblies, new AutoPersistenceModelGenerator().Generate(), "../../../../app/XXX.Web/NHibernate.config"); } [TearDown] public virtual void TearDown() { NHibernateSession.CloseAllSessions(); NHibernateSession.Reset(); } [Test] public void CanConfirmDatabaseMatchesMappings() { var allClassMetadata = NHibernateSession.GetDefaultSessionFactory().GetAllClassMetadata(); foreach (var entry in allClassMetadata) { NHibernateSession.Current.CreateCriteria(entry.Value.GetMappedClass(EntityMode.Poco)) .SetMaxResults(0).List(); } } /// <summary> /// Generates and outputs the database schema SQL to the console /// </summary> [Test] public void CanGenerateDatabaseSchema() { System.IO.TextWriter writeFile = new StreamWriter(@"d:/XXXSqlCreate.sql"); var session = NHibernateSession.GetDefaultSessionFactory().OpenSession(); new SchemaExport(configuration).Execute(true, false, false, session.Connection, writeFile); } private Configuration configuration; } I am trying to use: using FluentNHibernate.Automapping; using xxx.Core; using SharpArch.Data.NHibernate.FluentNHibernate; using FluentNHibernate.Automapping.Alterations; namespace xxx.Data.NHibernateMaps { public class x : IAutoMappingOverride<x> { public void Override(AutoMapping<Tx> mapping) { mapping.Map(x => x.text, "text").CustomSqlType("varchar(max)"); mapping.Map(x => x.url, "url").CustomSqlType("varchar(max)"); } } } To change the standard mapping of strings from NVARCHAR(255) to varchar(max). This is not picked up during the sql schema generation. I also tried: mapping.Map(x = x.text, "text").Length(100000); Any ideas? Thanks. Christian

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• objective C architecture question

  - by thekevinscott

  Hey folks, I'm currently teaching myself objective C. I've gone through the tutorials, but I find I learn best when slogging through a project of my own, so I've embarked on making a backgammon app. Now that I'm partway in, I'm realizing there's some overall architecture things I just don't understand. I've established a "player" class, a "piece" class, and a "board" class. A piece theoretically belongs to both a player and the board. For instance, a player has a color, and every turn makes a move; so the player owns his pieces. At the same time, when moving a piece, it has to check whether it's a valid move, whether there are pieces on the board, etc. From my reading it seems like it's frowned upon to reach across classes. For instance, when a player makes a move, where should the function live that moves the piece? Should it exist on board? This would be my instinct, as the board should decide whether a move is valid or not; but the piece needs to initialize that query, as its the one being moved, no? Any info to help a noob would be super appreciated. Thanks guys!

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• Best architecture for a social media app

  - by Sky

  Hey guys, Im working on promising project that develops a new social media app for web and mobile. We are at begin defining functionalities. Nevertheless, I'm thinking ahead on architecture. So I'm asking: 1 - Whats the best plataform to develop the core of this aplication that will have a Rest API interface. 2 - Whats the best database that will scale and grow with my application. As far as I researched, these were the answers I found most interesting: For database: Cassandra NoSQL DB, amazing scalabilty, amazing write performance, good read performance (will be improved on 0.6). I think i will choose that one. Zookeer for transactions on Cassandra. I think that 2 technologies rly good for that propose. What do you think guys? On the front end that will serve the REST API, i dont have a final candidate. For this one i have questions based on Perfomance X Scalabilty X Fast Development/Maintenance. Java or .Net As far as I researched, brings the best balance of this requisits. Python, pearl and Rail, has the best (Fast Development/Maintenance), but sux on all other. C or C++ I dont even consider, because its (Fast Development/Maintenance) sux... So what do you guy think about it?

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• Design Decision - Scaling out web based application's architecture

  - by Vadi

  This question is about design decision. I am currently working on a web project that will have 40K users to start with and in couple of month expected to grow 50M users (not concurrent users though). I would like to have a architecture that can be scaled out easily without much effort. In order to explain, I would like to use a trivial scenario. Lets say, User entities and services such as CreateUser, AuthenticateUser etc., are a simple method calls for the Page Controllers. But once the traffic increases, for example, authenticating user (or such services related to user entities) has to be moved out to a different internal server to spread the load. But at the same time using RPC calls over the network when the user count is 40K would become overkill. My proposal was to use IPC initially and when we need to scale out we can interally switch to TCP based RPC calls so that it can easily scale out. For example, I am referring to System.IO.Pipes.NamedPipeStreamServer to start with and move on to a TcpListener later on. If we have proper design that can encapsulate above said approach, it would easy for us to scale out services into multiple network servers but at the same time avoid network calls when the user count is small. Is this is a best approach? Any suggestions would be great .. Note: The database scaling is definetly the second phase optimization so we have already made architectural design in place to easily partition data when traffic increases. The primary bottleneck would be application servers over the time period.

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• Windows Workflow Foundation: Recommendations how to design architecture

  - by Petr Felzmann

  We are running several the same ASP.NET applications (one per customer) based on our custom framework (libraries). Each application use its own database (Initial Catalog in the term of connection string). Now we would like to add workflow capability (of course 4.0 ;) to the applications. So the particular workflows will be the same for all the applications only some initial settings of each workflow can vary, e.g. in one application the e-mail will be send to the user X, but in other application to the user Y. I have several general questions how to design architecture: (1) Can be the workflow database shared for all the applications? (2) Where to host workflow engine - inside our custom windows NT service or inside IIS? What are the criteria to choose the right host? (3) How the workflow engine should communicate with applications? Should application call some WCF endpoint API configured in workflow host or vice verse - should each application provide WCF endpoint API and workflow engine will call it? How then the workflow engine will identify applications? Both cases requires probably some application identifier as a parameter in API calls? (4) We would like to also store some information to the application databases based on the workflow states. Is it possible? Thanks for suggestions!

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• Commercial Website architecture question

  - by Maxime ARNSTAMM

  Hello everyone, I have to write an architecture case study but there are some things that i don't know, so i'd like some pointers on the following : The website must handle 5k simultaneous users. The backend is composed by a commercial software, some webservices, some message queues, and a database. I want to recommend to use Spring for the backend, to deal with the different elements, and to expose some Rest services. I also want to recommend wicket for the front (not the point here). What i don't know is : must i install the front and the back on the same tomcat server or two different ? and i am tempted to put two servers for the front, with a load balancer (no need for session replication in this case). But if i have two front servers, must i have two back servers ? i don't want to create some kind of bottleneck. Based on what i read on this blog a really huge charge is handle by one tomcat only for the first website mentionned. But i cannot find any info on this, so i can't tell if it seems plausible. If you can enlight me, so i can go on in my case study, that would be really helpful. Thanks :)

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• Architecture for new ASP.NET web application

  - by Anders Abel

  I'm maintaining an application which currently is just a web service (built with WCF) and a database backend. The web service is built in layers with a linq-to-sql data access part with core functionality in an own assembly and on top of that the web service assembly which contains the WCF code. The core assembly also handles all business logic rules (very few actually). The customer now wants a Web interface for the application instead of just accessing it through other applications which are consuming the web service. I'm quite lost on modern web application design, so I would like some advice on what architecture and frameworks to use for the web application. The web application will be using the same core assembly with business rules and the linq-to-sql data access layer as the web service. Some concepts I've thought about are: ASP.NET MVC Webforms AJAX controls - possibly leting the AJAX controls access the existing web service through JSON. Are there any more concepts I should look into? Which one is the best for a fresh project? The development tools are Visual Studio 2008 Team Edition for Developers targeting .NET 3.5. An upgrade to Visual Studio 2010 Premium (or maybe even Ultimate) is possible if it gives any benefits.

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• Determine target architecture of binary file in Linux (library or executable)

  - by Fernando Miguélez

  We have an issue related to a Java application running under a (rather old) FC3 on a Advantech POS board with a Via C3 processor. The java application has several compiled shared libs that are accessed via JNI. Via C3 processor is suppossed to be i686 compatible. Some time ago after installing Ubuntu 6.10 on a MiniItx board with the same processor I found out that the previous statement is not 100% true. The Ubuntu kernel hanged on startup due to the lack of some specific and optional instructions of the i686 set in the C3 processor. These instructions missing in C3 implementation of i686 set are used by default by GCC compiler when using i686 optimizations. The solution in this case was to go with a i386 compiled version of Ubuntu distribution. The base problem with the Java application is that the FC3 distribution was installed on the HD by cloning from an image of the HD of another PC, this time an Intel P4. Afterwards the distribution needed some hacking to have it running such as replacing some packages (such as the kernel one) with the i383 compiled version. The problem is that after working for a while the system completely hangs without a trace. I am afraid that some i686 code is left somewhere in the system and could be executed randomly at any time (for example after recovering from suspend mode or something like that). My question is: Is there any tool or way to find out at what specific architecture is an binary file (executable or library) aimed provided that "file" does not give so much information?

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• Importing data from third party datasource (open architecture design )

  - by mare

  How would you design an application (classes, interfaces in class library) in .NET when we have a fixed database design on our side and we need to support imports of data from third party data sources, which will most likely be in XML? For instance, let us say we have a Products table in our DB which has columns Id Title Description TaxLevel Price and on the other side we have for instance Products: ProductId ProdTitle Text BasicPrice Quantity. Currently I do it like this: Have the third party XML convert to classes and XSD's and then deserialize its contents into strong typed objects (what we get as a result of this process is classes like ThirdPartyProduct, ThirdPartyClassification, etc.). Then I have methods like this: InsertProduct(ThirdPartyProduct newproduct) I do not use interfaces at the moment but I would like them to. What I would like is implement something like public class Contoso_ProductSynchronization : ProductSynchronization InsertProduct(ContosoProduct p) where ProductSynchronization will be an interface or abstract class. There will most likely be many implementations of ProductSynchronization. I cannot hardcode the types - classes like ContosoProduct, NorthwindProduct might be created from the third party XML's (so preferably I would continue to use deserialization). Hopefully someone will understand what I'm trying to explain here. Just imagine you are the seller and you have numerous providers and each one uses their own proprietary XML format. I don't mind the development, which will of course be needed everytime new format appears, because it will only require 10-20 methods to be implemented, I just want the architecture to be open and support that.

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• What pattern is layered architecture in asp.net ?

  - by haansi

  Hi, I am a asp.net developer and don't know much about patterns and architecture. I will very thankful if you can please guide me here. In my web applications I use 4 layers. Web site project (having web forms + code behind cs files, user controls + code behind cs files, master pages + code behind cs files) CustomTypesLayer a class library (having custom types, enumerations, DTOs, constructers, get, set and validations) BusinessLogicLayer a class library (having all business logic, rules and all calls to DAL functions) DataAccessLayer a class library( having just classes communicating to database.) -My user interface just calls BusinessLogicLayer. BusinessLogicLayer do proecessign in it self and for data it calls DataAccessLayer funtions. -Web forms do not calls directly DAL. -CustomTypesLayer is shared by all layers. Please guide me is this approach a pattern ? I though it may be MVC or MVP but pages have there code behind files as well which are confusing me. If it is no patren is it near to some patren ? pleaes guide thanks

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• Entity and N-Tier architecture in C#

  - by acadia

  Hello, I have three tables as shown below Emp ---- empID int empName deptID empDetails ----------- empDetailsID int empID int empDocuments -------------- docID empID docName docType I am creating a entity class so that I can use n-tier architecture to do database transactions etc in C#. I started creating class for the same as shown below using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace employee { class emp { private int empID; private string empName; private int deptID; public int EmpID { get; set; } public string EmpName { get; set; } public int deptID { get; set; } } } My question is as empDetails and empDocuments are related to emp by empID. How do I have those in my emp class. I would appreciate if you can direct me to an example. Thanks

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• Pitfalls of the Architecture - Database based HTTP Request/Response Parsing

  - by Sam

  We have a current eCommerce Site that runs on ASP.NET and we hired a consultant to develop an new site bases on SOA. The new site architecture is as follows Web Application : Single Page Web Application (built on javascript/jquery templates - do not use any MVVM frameworks) that uses some javascript thrown all over the place. Service Layer : Very very light Service Layer that does not do anything other than calling a single stored procedure and pass in the entire http request. Database : The entire site content is in the database. The database does the heavy lifting of parsing the request and based on the HTTP method and some input parameter calls the appropriate Store Procedures or views and renders the result in JSON/XML. We have been told by them that this is built on latest and greatest technologies. I have a lot of concerns and of them given are the few Load on the Database SEO concerns for single page application as this is a public facing website Scalablity? Is this SOA? Cross Browser compatability (Site does not work in < IE9) Realistic implementaion of Single page application I know something is not right but I just need to validate my concerns here. Please help me.

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• Application Architecture using WCF and System.AddIn

  - by Silverhalide

  A little background -- we're designing an application that uses a client/server architecture consisting of: A server which loads server-side modules, potentially developed by other teams. A client which loads corresponding client-side modules (also potentially developed by those other teams; each client module corresponds with a server module). The client side communicates with the server side for general coordination, and as well as module specific tasks. (At this point, I think that means client talks to server, client modules talk to server modules.) Environment is .NET 3.5, and client side is WPF. The deployment scenario introduces the potential to upgrade the server, any server-side module, the client, and any client-side module independently. However, being able to "work" using mismatched versions is required. I'm therefore concerned about versioning issues. My thinking so far: A Windows Service for the server. Using System.AddIn for the server to load and communicate with the server modules will give us the greatest flexibility in terms of version compatability between server and server modules. The server and each server module vend WCF services for communication to the client side; communication between the server and a server module, or between two server modules use the AddIn contracts. (One advantage of this is that a module can expose a different interface within the server and outside it.) Similarly, the client uses System.AddIn to find, load, and communicate with the client modules. Client communications with client modules is via the AddIn interface; communications from the client and from client modules to the server side are via WCF. For maximum resilience, each module will run in a separate app-domain. In general, the system has modest performance requirements, so marshalling and crossing process boundaries is not expected to be a performance concern. (Performance requirement is basically summed up by: don't get in the way of the other parts of the system not described here.) My questions are around the idea of having two different communication and versioning models to work with which will be an added burden on our developers. System.AddIn seems quite powerful, but also a little unwieldly. (I'm also unsure of Microsoft's commitment to it in the future.) On the other hand, I'm not thrilled with WCF's versioning capabilities. I have a feeling that it would be possible to implement the System.AddIn view/adapter/contract system within WCF, but being fairly new to both technologies, I would have no idea of where to start. So... Am I on the right track here? Am I doing this the hard way? Are there gotchas I need to be aware of on this road? Thanks.

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• Architecture Suggestions/Recommendations for a Web Application with Sub-Apps

  - by user579218

  Hello. I’m starting to plan an architecture for a big web application, and I wanted to get suggestions and/or recommendations on where to begin and which technologies and/or frameworks to use. The application will be an Intranet-based web site using Windows authentication, running on IIS and using SQL Server and ASP.NET. It’ll need to be structured as a main/shell application with sub-applications that are “pluggable” based on some configuration settings. The main or shell application is to provide the overall user interface structure – header/footer, dynamically built tabs for each available sub-app, and a content area in which the sub-application will be loaded when the user clicks on the sub-application’s tab. So, on start-up of the main/shell application, configuration information will be queried from a database, and, based on the user and which of the sub-apps are available, the main or shell app would dynamically build tabs (or buttons or something) as a way to access each individual application. On start-up, the content area will be populated with the “home” sub-app. But, clicking on an sub-app tab will cause the content area to be populated with the sub-app corresponding to the tab. For example, we’re going to have a reports application, a display application, and probably a couple other distinct applications. On startup of the main/shell application, after determining who the user is, the main app will query the database to determine which sub-apps the user can use and build out the UI. Then the user can navigate between available sub-apps and do their work in each. Finally, the entire app and all sub-apps need to be a layered design with presentation, service, business, and data access layers, as well as cross-cutting objects for things such as logging, exception handling, etc. Anyway, my questions revolve around where to begin to plan something like this application. What technologies/frameworks would work best in developing a solution for this application? MVC? MVP? WCSF? EF? NHibernate? Enterprise Library? Repository Pattern? Others???? I know all these technologies/frameworks are not used for the same purpose, but knowing which ones to focus on is a little overwhelming. Which ones would be the best choice(s) for a solution? Which ones work well together for an end-to-end design? How would one structure the VS project for something like this? Thanks!

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• Announcing the ADF Architecture Square at OOW12

  - by Chris Muir

  The ADF product management team are happy to announce at Oracle Open World the publication of the ADF Architecture Square: Over the last number of years Oracle has recognized that many customers have matured their ADF skills and are now looking for information on advanced concepts beyond the how-do-I-get-this-poplist-to-work type questions.  In order to satisfy this demand we've devised the ADF Architecture Square where papers, presentations and demos will consider such broad software engineering concepts as ADF architecture, development and testing, building and deployment, and infrastructure.   If you have a look at the site right now it's a rather modest affair, but we hope to continue to expand the content to give further guidance and information to help shortcut your ADF project needs.  Either watch the website or follow our dedicated @adfarchsquare twitter feed.

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• Architecture for a business objects / database access layer

  - by gregmac

  For various reasons, we are writing a new business objects/data storage library. One of the requirements of this layer is to separate the logic of the business rules, and the actual data storage layer. It is possible to have multiple data storage layers that implement access to the same object - for example, a main "database" data storage source that implements most objects, and another "ldap" source that implements a User object. In this scenario, User can optionally come from an LDAP source, perhaps with slightly different functionality (eg, not possible to save/update the User object), but otherwise it is used by the application the same way. Another data storage type might be a web service, or an external database. There are two main ways we are looking at implementing this, and me and a co-worker disagree on a fundamental level which is correct. I'd like some advice on which one is the best to use. I'll try to keep my descriptions of each as neutral as possible, as I'm looking for some objective view points here. Business objects are base classes, and data storage objects inherit business objects. Client code deals with data storage objects. In this case, common business rules are inherited by each data storage object, and it is the data storage objects that are directly used by the client code. This has the implication that client code determines which data storage method to use for a given object, because it has to explicitly declare an instance to that type of object. Client code needs to explicitly know connection information for each data storage type it is using. If a data storage layer implements different functionality for a given object, client code explicitly knows about it at compile time because the object looks different. If the data storage method is changed, client code has to be updated. Business objects encapsulate data storage objects. In this case, business objects are directly used by client application. Client application passes along base connection information to business layer. Decision about which data storage method a given object uses is made by business object code. Connection information would be a chunk of data taken from a config file (client app does not really know/care about details of it), which may be a single connection string for a database, or several pieces connection strings for various data storage types. Additional data storage connection types could also be read from another spot - eg, a configuration table in a database that specifies URLs to various web services. The benefit here is that if a new data storage method is added to an existing object, a configuration setting can be set at runtime to determine which method to use, and it is completely transparent to the client applications. Client apps do not need to be modified if data storage method for a given object changes. Business objects are base classes, data source objects inherit from business objects. Client code deals primarily with base classes. This is similar to the first method, but client code declares variables of the base business object types, and Load()/Create()/etc static methods on the business objects return the appropriate data source-typed objects. The architecture of this solution is similar to the first method, but the main difference is the decision about which data storage object to use for a given business object is made by the business layer, not the client code. I know there are already existing ORM libraries that provide some of this functionality, but please discount those for now (there is the possibility that a data storage layer is implemented with one of these ORM libraries) - also note I'm deliberately not telling you what language is being used here, other than that it is strongly typed. I'm looking for some general advice here on which method is better to use (or feel free to suggest something else), and why.

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• Domain Validation in a CQRS architecture

  - by Jupaol

  Basically I want to know if there is a better way to validate my domain entities. This is how I am planning to do it but I would like your opinion The first approach I considered was: class Customer : EntityBase<Customer> { public void ChangeEmail(string email) { if(string.IsNullOrWhitespace(email)) throw new DomainException(“...”); if(!email.IsEmail()) throw new DomainException(); if(email.Contains(“@mailinator.com”)) throw new DomainException(); } } I actually do not like this validation because even when I am encapsulating the validation logic in the correct entity, this is violating the Open/Close principle (Open for extension but Close for modification) and I have found that violating this principle, code maintenance becomes a real pain when the application grows up in complexity. Why? Because domain rules change more often than we would like to admit, and if the rules are hidden and embedded in an entity like this, they are hard to test, hard to read, hard to maintain but the real reason why I do not like this approach is: if the validation rules change, I have to come and edit my domain entity. This has been a really simple example but in RL the validation could be more complex So following the philosophy of Udi Dahan, making roles explicit, and the recommendation from Eric Evans in the blue book, the next try was to implement the specification pattern, something like this class EmailDomainIsAllowedSpecification : IDomainSpecification<Customer> { private INotAllowedEmailDomainsResolver invalidEmailDomainsResolver; public bool IsSatisfiedBy(Customer customer) { return !this.invalidEmailDomainsResolver.GetInvalidEmailDomains().Contains(customer.Email); } } But then I realize that in order to follow this approach I had to mutate my entities first in order to pass the value being valdiated, in this case the email, but mutating them would cause my domain events being fired which I wouldn’t like to happen until the new email is valid So after considering these approaches, I came out with this one, since I am going to implement a CQRS architecture: class EmailDomainIsAllowedValidator : IDomainInvariantValidator<Customer, ChangeEmailCommand> { public void IsValid(Customer entity, ChangeEmailCommand command) { if(!command.Email.HasValidDomain()) throw new DomainException(“...”); } } Well that’s the main idea, the entity is passed to the validator in case we need some value from the entity to perform the validation, the command contains the data coming from the user and since the validators are considered injectable objects they could have external dependencies injected if the validation requires it. Now the dilemma, I am happy with a design like this because my validation is encapsulated in individual objects which brings many advantages: easy unit test, easy to maintain, domain invariants are explicitly expressed using the Ubiquitous Language, easy to extend, validation logic is centralized and validators can be used together to enforce complex domain rules. And even when I know I am placing the validation of my entities outside of them (You could argue a code smell - Anemic Domain) but I think the trade-off is acceptable But there is one thing that I have not figured out how to implement it in a clean way. How should I use this components... Since they will be injected, they won’t fit naturally inside my domain entities, so basically I see two options: Pass the validators to each method of my entity Validate my objects externally (from the command handler) I am not happy with the option 1 so I would explain how I would do it with the option 2 class ChangeEmailCommandHandler : ICommandHandler<ChangeEmailCommand> { public void Execute(ChangeEmailCommand command) { private IEnumerable<IDomainInvariantValidator> validators; // here I would get the validators required for this command injected, and in here I would validate them, something like this using (var t = this.unitOfWork.BeginTransaction()) { var customer = this.unitOfWork.Get<Customer>(command.CustomerId); this.validators.ForEach(x =. x.IsValid(customer, command)); // here I know the command is valid // the call to ChangeEmail will fire domain events as needed customer.ChangeEmail(command.Email); t.Commit(); } } } Well this is it. Can you give me your thoughts about this or share your experiences with Domain entities validation EDIT I think it is not clear from my question, but the real problem is: Hiding the domain rules has serious implications in the future maintainability of the application, and also domain rules change often during the life-cycle of the app. Hence implementing them with this in mind would let us extend them easily. Now imagine in the future a rules engine is implemented, if the rules are encapsulated outside of the domain entities, this change would be easier to implement

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• What does "enterprise" means in relation to software architecture?

  - by SkonJeet

  I see the term "enterprise" being thrown around software developers and programmers a lot and used loosely it seems. en·ter·prise/'ent?r?priz/ Noun: A project or undertaking, typically one that is difficult or requires effort. Initiative and resourcefulness. Can someone please clarify what this term actually encompasses? "At an enterprise level", "enterprise scale"? There are even "enterprise editions" of things. What exactly does it mean? It obviously doesn't make sense judging by the above definition so more specifically to software what does one mean when using the word enterprise? EDIT: To add a spin on this - how does this term then fit into phrases such as Enterprise Framework Model? What does data access and data context have to do with company-wide descriptions?

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• What should be the architecture of an urban game system?

  - by pmichna

  I'm going to develop an urban game using a telco API for phone geolocation and sending/receiving messages. A player would pick up one of the scenarios, move around the city and when he hits a given location, he gets a message and possibly has to answer it. I'm wondering, what approach would be the best in my case. I came up with this general idea: Web application as a user interface (user registration, players ranking, scenarios editing) written in Ruby on Rails. Game server (hosting games, game logic like checking players location, sending and receiving messages) written in Ruby. Database (users, scores, scenarios etc.), probably MySQL or someother open source DB. I want to learn Ruby and RoR, that's why I chose these language and framework. Do you think it's a good choice for a game server? Another question: is this project division good? I mean, I have little experience with Ruby and Rails - that's why I'm asking. Maybe it's better to have web application merged with game server and somehow have the server hosting RoR application do the tasks like mobile phone pinging and message sending? How would that be performed? Maybe this is worth mentioning: the API is RESTful, most results are JSON, few are XML.

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