NFRs

Description

Availability

The application of this pattern does not in itself improve the availability of the system. However, application server architecture lays the foundation for a highly-available system.

Performance

Performance is likely to be significantly improved. Whereas we had all the semi-autonomous applications collaborating (using some form of inter-process or inter-server communication) to render pages or perform complex functions, now we have a single application, although parts of this may still require inter-process communication, depending on implementation choices.

Scalability

The application of this pattern does not in itself improve the scalability of the system. However, application server architecture lays the foundation for a highly scalable system.

Security

Security is marginally improved due to having only one application and one database to worry about securing.

Manageability

Manageability is significantly improved: as earlier we had many applications to manage, now we only have one. Even when we add more complexity to the architecture to achieve scalability, and so on. Application server architecture lays the foundation for a more manageable system.

Maintainability

Because all the logically separate software 'modules' are part of the same application, we don't have to worry about complex communication mechanisms. However, we have not lost the benefits of having well-defined sets of functionality which can, potentially, help to isolate bugs. On the whole, maintainability is improved.

Flexibility

This type of system architecture is flexible as we have a partitioning, which gives us flexibility.

Portability

Not affected.

Cost

Application server architecture provides a foundation where manageability, performance, availability, and scalability can be addressed more easily (and therefore more cheaply). Running the application in the .NET framework or on a JEE application server can potentially reduce costs; the cost of purchasing the infrastructure can easily be offset by the cost of building all the functionality provided from scratch.