Patterns: Implementing Self-Service in an SOA Environment

Chapter 9. JSF front-end scenario 241

9.2 System design overview

This section discusses the system design of the front-end of the ITSOMart

application. Note that we have already extensively covered the topic of front-end

application design on section 7.2, “Application structure” on page 141. However,

the intent of this section is to use the real example of the ITSOMart application to

illustrate how one would match the needs of an application to the design

approaches previously discussed. We then reinforce the concepts by describing

how the designed approach is specifically mapped to the ITSOMart application.

This section also tangentially illustrates the modeling capabilities of Rational

Software Architect. All diagrams in this section were constructed using Rational

Software Architect.

9.2.1 Design considerations

Before designing an application, it is critical to understand your guiding

principles. Aside from the obvious goal of fullfilling the customer requirements,

you need to identify the goals you are trying to achieve with your system design

approach.

Goals can vary from application to application, so in this section we focus

specifically in the ones we considered when designing the ITSOMart system.

Nonetheless, these are general enough goals which are likely applicable to most

self-service applications. We first examine these principles and goals below, then

the component model and object model sections illustrate how they map to our

selected design approach.

򐂰 Design must separate the presentation layer from business logic.

The term

separate presentation from business logic has been a staple in user

interface design for decades now. The basic idea is that a good user interface

design should keep the rendering of screens separate from the application

logic which manages the information displayed.

User interface design is about presenting information in an aesthetically

pleasing fashion to end customers. Beyond a simple choice of technology, a

graphical user interface (GUI) design might involve a wide variety of human

factor guidelines, ranging from recommended types of menu bars, to which

colors are psychologically more apt to grab a customer’s attention.

Languages supporting GUI implementation, such as HTML or Java, generally

support multiple ways of presenting data. The choice of the presentation

should be driven by human factors guidelines.

Conversely, the design of the of the application code responsible for

implementing the business logic is influenced by more standard IT drivers

such as performance, storage capacity, code reuse, reliability, and so forth.