How to Architect an Application

Many of us are developing and maintaining web applications as part of our daily routine. But most of us still struggle to maintain the web application due to lack of flexibility and separation of concerns.

In my experience I have seen the business requirements continuallly changing based on the business priorities and the application should support the changing business needs.

Now, let's get into the business of how to architect an application.

For the last decade or so, many tools and frameworks are created to address the database requirements. Most of them are like reverse engineering, where you create the database schema and objects and then build application logic on top of it.

Because of rapid changes in business requirements, it is very difficult to maintain the database changes. For example, there might be one additional property you might want to add or change. For existing property characteristics you always need to do an impact analysis everywhere the dependency is created and it very hard to do that in very large projects.

If it is a small or medium-seized project then prefer creating the database and object by hand and then use the ORM frameworks to generate the business objects to use them in your application logic.

For the list of ORM tools visit the URL http://www.theserverside.net/news/thread.tss?thread_id=29914

If it is large sized project then prefer using modeling tools to model the data model. A good thing about the data modeling tools are that the objects are integrated and easy to maintain.

Some of the modeling tools are Microsoft Entity Framework and Deklarit. You can visit their home page to get more information.

The Data Access Layer (DAL) is the separate layer whose responsibility is to handle the database operations. Data operations can be Create, Read, Update or Delete (CRUD) operations.

Now if you are wondering how to create the DAL layer then the following is the procedure:

• If you decided to use the ORM frameworks then they will generate the data objects based on your database objects. You don't need to write a single line of code to create and maintain the data access library.
• If you have decided the data modeling tool then the data modeling tool will be responsible for creating the database objects and generate the DAL library. The same DAL library can be used to do the CRUD operations.

Now we come to the important piece of the business logic. The Business Logic Layer (BLL), or sometimes people call it the Business Access Layer (BAL) is the layer where the application business logic exists.

Why do I really bother about separating the business layer from the data access layer?