Software Design Methodology

Software Architecture Design 233

– Scenario 3: Upgrade the database management system Oracle 4 to a higher

version Oracle 6;

– Scenario 4: Change the database management system from Oracle to

Microsoft’s Access.

– Scenario 5: Change the middleware of the system from CORBA to DCOM.

Another type of change in software environment is the changes in the

software systems that the application interoperates with. For example, suppose that

a graphic editor that enables the user to draw various types of diagrams is designed

to interoperate with a particular word processor. To change the word processor that

the graphic editor is supposed to interact with is a change of the graphic editor’s

software environment. The following are examples of such scenarios.

– Scenario 6: A web-based application that links to a specific website that

provides an online map. The website that provides the online map changes

its web address, and/or the way online maps are requested.

– Scenario 7: A shopbot software agent helps the users to compare the prices

of books that online bookstores on the web offer for online shopping. An

online bookstore that the shopbot links to changes its format of messages in

the way that the prices of books are requested.

9.2.4 Changes of software components

With the rapid development of software component technology and availability of

COTS (Components Off-The-Shelve) components and shareware, more and more

software developers use third-party software components to reduce development

costs and speed up development processes. In house components are also becoming

more and more widely reused in software development. Such components often

evolve for many reasons, such as bugs fixed. An application software system often

needs to be modified due to the changes to the components either to take advantage

of the availability of better components or forced to make modifications because,

say, the component provider is no longer able to provide the support, or a free

component is no longer free, etc. The following are some examples of such

scenarios.

– Scenario 1: The representation of data produced by a new version of a third

party component is changed.

– Scenario 2: The representation of the data required by a new version of a

third party component is changed.

– Scenario 3: The format of messages sent to and received from a new version

of a third party component is modified.