Sunday, March 23, 2014

JQuery: Deferred Object

The Deferred object, introduced in jQuery 1.5, is a chainable utility object created by calling the jQuery.Deferred() method. It can register multiple callbacks into callback queues, invoke callback queues, and relay the success or failure state of any synchronous or asynchronous function.
In computer science, future, promise, and delay refer to constructs used for synchronizing in some concurrent programming languages. They describe an object that acts as a proxy for a result that is initially unknown, usually because the computation of its value is yet incomplete. A deferred is an object representing work that is not yet done and a promise is an object representing a value that is not yet known. In other words, promises / deferreds allow us to represent ‘simple’ tasks and can be easily combined to represent complex tasks and their flows, allowing for fine-grained control over sequencing. This means we can write asynchronous JavaScript parallel to how we write synchronous code. Additionally, promises make it relatively simple to abstract small pieces of functionality shared across multiple asynchronous tasks.
Similar to jQuery object, Deferred object is also chainable. $.Deferred() / jQuery.Deferred() is a constructor that creates a new deferred object. A Deferred object starts in the pending state. Any callbacks added to the object with deferred.then(), deferred.always(), deferred.done(), or are queued to be executed later. Calling deferred.resolve() or deferred.resolveWith() transitions the Deferred into the resolved state and immediately executes any doneCallbacks that are set. Calling deferred.reject() or deferred.rejectWith() transitions the Deferred into the rejected state and immediately executes any failCallbacks that are set. Once the object has entered the resolved or rejected state, it stays in that state. Callbacks can still be added to the resolved or rejected Deferred — they will execute immediately.
Key Points:
  • deferred.always(), deferred.done(), return the deferred object.
  • deferred.then(), deferred.when(), .promise() return a promise.
  • $.ajax() and $.get() return promise objects
  • instead of using .resolveWith() and .rejectWith(), you can call resolve with the context you want it to inherit
  • pass the deferred.promise() around instead of the deferred itself as the deferred object itself cannot be resolved or rejected through it.

Friday, February 28, 2014

Principles of Software Architecture

Key Design Principles
When getting started with application design, keep in mind the key principles that will help to create an architecture that adheres to proven principles, minimizes costs and maintenance requirements, and promotes usability and extendability. The key principles are:
  • Separation of concerns. Divide application into distinct features with as little overlap in functionality as possible. The important factor is minimization of interaction points to achieve high cohesion and low coupling. However, separating functionality at the wrong boundaries can result in high coupling and complexity between features even though the contained functionality within a feature does not significantly overlap.
  • Single Responsibility principle. Each component or module should be responsible for only a specific feature or functionality, or aggregation of cohesive functionality.
  • Principle of Least Knowledge (also known as the Law of Demeter or LoD). A component or object should not know about internal details of other components or objects.
  • Don’t repeat yourself (DRY). In terms of application design, specific functionality should be implemented in only one component; the functionality should not be duplicated in any other component.
  • Minimize upfront design. Only design what is necessary. In some cases, it might require upfront comprehensive design and testing if the cost of development or a failure in the design is very high. In other cases, especially for agile development, big design upfront (BDUF) can be avoid. If  application requirements are unclear, or if there is a possibility of the design evolving over time, avoid making a large design effort prematurely. This principle is sometimes known as YAGNI ("You ain’t gonna need it").
Key Design Considerations
The major design considerration listed as follow:
  • Determine the Application Type
  • Determine the Deployment Strategy
  • Determine the Appropriate Technologies
  • Determine the Quality Attributes
  • Determine the Crosscutting Concerns
Below figure illustrates common application architecture with components grouped by different areas of concern.

Thursday, January 9, 2014

JSLint : Static program analysis tool

JSLint is a static program analysis tool. It was developed by Douglas Crockford. Static program analysis is the interpretation of computer software that is performed with actually executing. JSLint is used for checking if JavaScript source code complies with coding rules.It can be referred as code quality tool.
JavaScript is a young-for-its-age language. It was originally intended to do small tasks in webpages, tasks for which Java was too heavy and clumsy. But JavaScript is a surprisingly capable language, and it is now being used in larger projects. Many of the features that were intended to make the language easy to use are troublesome when projects become complicated. A lint for JavaScript is needed: JSLint, a JavaScript syntax checker and validator.
JSLint takes a JavaScript source and scans it. If it finds a problem, it returns a message describing the problem and an approximate location within the source. The problem is not necessarily a syntax error, although it often is. JSLint looks at some style conventions as well as structural problems. It does not prove that your program is correct. It just provides another set of eyes to help spot problems.
JSLint is provided primarily as an online tool, but there are also command-line adaptations. JSLint.VS2012 extension also available for Microsoft Visual Studio 2012.
Also, JSONLint is the JSON validator availabe for online use.

JSLint.NET is a wrapper for Douglas Crockford's JSLint, the JavaScript code quality tool. It can validate JavaScript anywhere .NET runs.
At it's core, the JSLint.NET project aims to provide:
  • a complete, accurate and up-to-date wrapper for JSLint
  • an interface that's natural for .NET developers while staying true-to-source
  • a suite of valuable tools that assist JavaScript developers working on Microsoft platforms

Tuesday, December 31, 2013

Happy New Year 2014

I wish u to have a
Sweetest Sunday,
Marvelous Monday,
Tasty Tuesday,
Wonderful Wednesday,
Thankful Thursday,
Friendly Friday,
Successful Saturday,
Have a great Year,


What is Web API?
Web API is a new web application runtime that builds on the lessons and patterns proven in ASP.NET MVC. Using a simple controller paradigm, Web API enables a developer to create simple HTTP web services with very little code and configuration. WebAPI is an ideal platform for building pure HTTP based services where the request and response happens with HTTP protocol. The client can make a GET, PUT, POST, and DELETE request and get the WebAPI response appropriately.
ASP.NET Web API is a framework that makes it easy to build HTTP services that reach a broad range of clients, including browsers and mobile devices. ASP.NET Web API is an ideal platform for building RESTful applications on the .NET Framework.
WebAPI is
  • An HTTP Service
  • Designed for broad reach
  • Uses HTTP as an Application protocol, not a transport protocol
Why Web API?
Today, a web-based application is not enough to reach it's customers. People are very smart, they are using iphone, mobile, tablets etc. devices in its daily life. These devices also have a lot of apps for making the life easy. Actually, we are moving from the web towards apps world.
Web API is the great framework for exposing your data and service to different-different devices. Moreover Web API is open source an ideal platform for building REST-ful services over the .NET Framework. Unlike WCF Rest service, it use the full featues of HTTP (like URIs, request/response headers, caching, versioning, various content formats) and you don't need to define any extra config settings for different devices unlike WCF Rest service.
How Web API is different from WCF
Enables building services that support multiple transport protocols (HTTP, TCP, UDP, and custom transports) and allows switching between them. HTTP only. First-class programming model for HTTP. More suitable for access from various browsers, mobile devices etc enabling wide reach.
Enables building services that support multiple encodings (Text, MTOM, and Binary) of the same message type and allows switching between them. Enables building Web APIs that support wide variety of media types including XML, JSON etc.
Supports building services with WS-* standards like Reliable Messaging, Transactions, Message Security. Uses basic protocol and formats such as HTTP, WebSockets, SSL, JQuery, JSON, and XML. There is no support for higher level protocols such as Reliable Messaging or Transactions.
Supports Request-Reply, One Way, and Duplex message exchange patterns. HTTP is request/response but additional patterns can be supported through SignalRand WebSockets integration.
WCF SOAP services can be described in WSDL allowing automated tools to generate client proxies even for services with complex schemas. There is a variety of ways to describe a Web API ranging from auto-generated HTML help page describing snippets to structured metadata for OData integrated APIs.
Ships with the .NET framework. Ships with .NET framework but is open-source and is also available out-of-band as independent download.
Web API Features
  • It supports convention-based CRUD Actions since it works with HTTP verbs GET, POST, PUT and DELETE.
  • Responses have an Accept header and HTTP status code.
  • Responses are formatted by Web API’s MediaTypeFormatter into JSON, XML or whatever format you want to add as a MediaTypeFormatter.
  • It may accepts and generates the content which may not be object oriented like images, PDF files etc.
  • It has automatic support for OData. Hence by placing the new [Queryable] attribute on a controller method that returns IQueryable, clients can use the method for OData query composition.
  • It can be hosted with in the applicaion or on IIS.
  • It also supports the MVC features such as routing, controllers, action results, filter, model binders, IOC container or dependency injection that makes it more simple and robust.

Friday, December 27, 2013

XBRL : eXtensible Business Reporting Language

XBRL (eXtensible Business Reporting Language) is a freely available and global standard for exchanging business information. XBRL allows the expression of semantic meaning commonly required in business reporting. The goal of XBRL is to standardize the automation of business intelligence (BI).
  • XBRL International is a not-for-profit consortium of approximately 650 companies and agencies worldwide working together to build the XBRL language and promote and support its adoption
  • XBRL is XML-based, it uses the XML syntax and related XML technologies
  • Effort had began in 1998 and has produced a variety of specifications and taxonomies
  • It is language for the electronic communication of business and financial data
  • It is an open standard which supports information modeling and the expression of semantic meaning commonly required in business reporting
  • It provides major benefits in the preparation, analysis and communication of business information.
  • It offers cost savings, greater efficiency and improved accuracy and reliability to all those involved in supplying or using financial data. 
  • XBRL is a standards-based way to communicate business and financial information.
  • These communications are defined by metadata set out in taxonomies.
  • Taxonomies capture the definition of individual reporting concepts as well as the relationships between concepts and other semantic meaning.
  • Provides identifying tag for each individual item of data such that it can be used by name
  • The basis for this technology is a "tagging" process by which each value, item, and descriptor, etc. in the exchanged information can be given a unique set of tags with which to describe it. Using these tags, computer programs can read the data without human intervention.
For more information:

Monday, December 9, 2013

Hekaton : In-Memory Optimization

Hekaton : The codename for a Microsoft project that will provide support for mixing in-memory database tables with more traditional on-disk tables in the same database. These hybrid databases will be able to dynamically handle both in-memory and on-disk storage in the same database for optimal performance and reliability. Traditional RDBMS architecture was designed when memory resources were expensive, and was optimized for disk I/O. Modern hardware has much more memory, which affects database design principles dramatically. Modern design can now optimize for a working set stored entirely in main memory. Hekaton fully provides ACID database properties.
Project Hekaton will enable Microsoft to compete in the in-memory database market with products like Oracle Database's Exadata and Exalytics appliance options and SAP Hana.
This SQL Server In-memory OLTP capability is released in SQL 2014 version. In-Memory OLTP is a memory-optimized OLTP database engine for SQL Server. Depending on the reason for poor performance with your disk-based tables, In-Memory OLTP can help you achieve significant performance and scalability gains by using,
  • Algorithms that are optimized for accessing memory-resident data.
  • Optimistic concurrency control that eliminates logical locks.
  • Lock free objects are used to access all data. Threads that perform transactional work don’t use locks or latches for concurrency control.
  • Natively compiled stored procedures result in orders of magnitude reduction in the engine code path.
Use of main memory can result in a few percentage points of performance improvement, to 20 times performance improvement.