Presentation Services

An important variation on the themes addressed in this book is the presentation service, which provides business data along with a stream of technical detail for constructing a graphical interface. The interface in turn lets the user interact with the data and access remote services and other software.

Different kinds of presentation services are in use. Although a comprehensive review is outside our scope, let us introduce a kind of presentation service that is widely used.

As Figure 1.2 illustrates, a portal is software that resides on a server and coordinates different interfaces, each affecting a different area of a Web page. From the perspective of a user, the output of a portal can provide a variety of news, business interaction, and entertainment, although an employee who accesses a company's internal portal is working primarily with applications that support the company's business.

Figure 1.2: Portal technology

Each application is controlled by a portlet, which is a unit of software that contributes sections of markup language such as Hypertext Markup Language (HTML). The portal collects those sections and submits them to devices such as Web browsers and personal digital assistants.

Portal technology empowers the user, who can select a subset of applications and may be able to customize the runtime behavior of individual portlets. Portals can even retain user preferences so that the experience is individualized as soon as a user logs on.

Traditionally, the portlets resided on the same server as the portal. In a natural extension of the technology, the portal requests data from a set of remote portlets, each of which acts as a presentation service. The standard that guides the interaction between portals and remote portlets is Web Services for Remote Portlets, as referenced in Appendix A.