An architecture for distributed applications on the Internet: Overview of the Microsoft.Net Framework

Journal of SMET Education : Innovations and Research, Jan-Jun 2003 by Barnett, Bryan, Kirtland, Mary, Ganapathy, Mythreyee

ADO.NET components have been designed to separate data access from data manipulation. Data access components include the Connection, Command, DataReader, and DataAdapter objects, and are used to fill data sets from data stores and to resolve changes to the data set back to the store. The NET data provider is designed to be lightweight, creating a minimal layer between the data source and your code, increasing performance without sacrificing functionality.

Another critical innovation in ADO.NET is strong support for handling XML data. In ADO, all data can be viewed as XML, and just as DataReaders XmlReaders expose efficient stream access to XML Data. Developers use a DataNavigator for scrolling and editing an in-memory XmlDocument.

DataNavigators are functionally equivalent to the WK Document Object Model (DOM), but are more efficient and provide an object model that maps nicely to the relational data view. DataNavigators support XPath syntax for navigating the data stream. ADO also provides an XMLDocument class for developers who want to continue to use the DOM as an object model for XML rather than the more efficient DataNavigator model.

Since all data can be viewed as XML, developers can take advantage of transformation and validation services for any data which are provided directly through the ADO.NET class libraries. ADO.NET supports schemas defined via DTDs, XSD, or XDR. The .NET Framework provides a specific transformation component that supports the W3C XSL Transformations (XSLT) specification, and also provides a validation engine that uses XML Schemas to validate an XmlReader.

Programming and Application Models in.NET

The ultimate reason for having a distributed application architecture is, of course, to be able to create applications. In today's world there are at least two basic types of applications, which have, traditionally been programmed in sometimes very different ways.

On the one hand are traditional client applications with complete GUI interfaces, programmed using either command line compilers or visual development environments to create executable packages for local deployment. On the other hand Web programming combines at least three different elements: a client side interface done through HTML, client-side scripting interwoven into the presentation code, and server side scripting in any of a number of different languages or implementation models from ASP to CGI scripting.

Though we have heretofore focused on NET as an architecture for Internetbased Web applications, the new platform programming model supports both standard programming of client applications and Web application programming. But the new architecture seeks to simplify the developer's learning curve and task by offering a unified visual programming model that is the same across both domains. Let's take a brief look at programming in each of the two.

Windows(R) Forms

Developers writing client applications for Windows can use what is now called the Win Forms application model which combines the best features of the popular forms-based visual programming style of Visual Basic with the full power of traditional MFC user interface classes. In addition Win Forms provides full access to existing ActiveX controls and new features of Windows 2000 or Windows XP, such as transparent, layered, and floating windows.