IIS, Internet Information Server, provides the DNA application with the rendering engine needed to publish application content to browsers. By using HTTP to deliver a lightweight presentation layer, the DNA application gains flexibility, quicker implementation and can support and deploy to an unlimited number of clients.
At the same time, DNA applications are required to interact with business components to perform some business functions. The results are then conveyed via the response to the browser clients. However, a web server that only returned static HTML pages would be of no use within the structure of DNA. With a need to call COM objects and via such objects access databases, file systems, line of business application servers such as Email, work flow and document management repositories; a flexible, on-demand interpreter is required to succinctly implement the communication between the business components within the Business Logic layer and the Web Server in the Presentation layer. This "glue" is Active Server Pages and the scripting model. Before discussing the role of scripting and ASP in the DNA application, the following lists the other functionality IIS provides within the DNA framework.
So where does ASP and scripting fit?
Active Server Pages and the scripting environment act as the glue between the Web Server and it's content delivery, the business components and even in some cases the data layer (in some circumstances the data and business layers are transparently implemented very close together.
By allowing scripts to be embedded into standard HTML files many possibilities are raised, some of these are covered in other sections of this tutorial. With scripting and ASP it is possible to call the business layer objects, call data sources and manage work flow process while being able to respond back to the client any information necessary.