| There is a potentially endless variety of fortresses . Historically I have focused on five main types. At some recent workshops I have conducted , participants have reached a consensus that one more type would be useful, so now we are officially up to six. Some organizations may find it convenient to add types I have not considered . So don't consider this a final list, but rather a collection of software fortress patterns. In any case, here is my current list of the six "standard" fortress types, along with the responsibilities of each and the abbreviations I use to refer to them throughout the book. I will give only an overview here: -
Business application fortress ( BAF ). Represented in my illustrations as the fuzzy Viking, the BAF is the most common fortress type. The BAF is the fortress that runs your business. When it is working hard, you are making money. When it is idle, you are not making money. Because no doubt you prefer to be making money rather than not making money, you want to make sure this fortress is capable of working as hard as possible. Typically the BAF runs transactions against high-end databases. An example of a business application fortress is inventory control. -
Treaty management fortress ( TMF ). Represented in my illustrations as a conductor, the TMF is a fortress that manages relationships between other fortresses. These relationships are called treaties . I will explain the treaty concept shortly. -
Legacy fortress ( LF ). Represented in my illustrations as a dinosaur, the LF is a fortress that wraps a legacy system. Wrapping a legacy system allows that system to participate in the overall software fortress approach without your having to rewrite working, mission-critical systems. -
Presentation fortress ( PF ). Represented in my illustrations as an artist's drawing board, the PF is responsible for dealing with browser clients over the Internet. It accepts HTTP requests and delivers HTML-like responses. It does not run any business logic, but typically interacts closely with business application fortresses to fulfill client requests. -
Web service fortress ( WSF ). Represented in my illustrations as a wizard, the WSF is responsible for dealing with program matic requests over the Internet. It accepts SOAP requests delivered over HTTP and delivers SOAP-style responses. Like the presentation fortress, it runs no business logic but has a fairly intimate relationship (for software fortresses!) with one or more back-end business application fortresses. -
Service fortress ( SF ). The SF is the most recent addition to the fortress collection. It is represented in my figures as a fairy and is a fortress that provides services to other fortresses. Such a service might be a wrapping around a standard operating system service, such as .NET's Active Directory, or it could be your own implementation of a service that several fortresses will need, such as a compensatory transaction manager. Certain fortress types may overlap somewhat. A business appli cation fortress might manage some simple treaties. A presentation fortress might contain some minor business application functionality, as long as that functionality has minimal security requirements. Treaty management fortresses often include service functionality. |
