While the enterprise procurement application in its present form addresses the basic functional requirements of ordering parts, traditionally enterprise computing has had much stronger non-functional requirements which the current architecture does not address. The challenge is, therefore, to meet the following non-functional requirements to make the application truly dependable:

  • Configurability Enterprises live and die on the ability to react quickly to market conditions. Those enterprises whose computing systems and processes can be reconfigured quickly gain advantage in the market place.

  • Transactionality High quality data is central to the successful enterprise and the ability to maintain the consistency of that data is paramount, especially where business processes are automated. Failure to guard against inconsistent data is a real Achilles' heel for any wired enterprise.

  • Security Trading partners must be able to identify those parties they are interacting with, and be assured that the messages exchanged are not tampered with.[1]

    [1] At time of writing, there are no freely available WS-Security implementations to use to secure the application. Instead, we assume that transport-level security mechanisms like HTTPS can be used to implement privacy and message integrity concerns, as well as (via certificates) to address authenticity concerns.

  • Mobility Like the ability to reconfigure processes quickly, mobility is a key factor in business agility. A modern enterprise needs to empower its people wherever they may be and so the IT infrastructure must be equally mobile.

Given the modular and extensible nature of Web services, we can add each of these features into our architecture in a piecemeal fashion, building up the overall functionality of the system one step at a time until we can support all of our non-functional requirements, as shown in Figure 13-1.

Figure 13-1. A Secure, Mobile, Configurable, Transaction-Aware Web Services-based Application


It should be kept in mind that while the overall architecture of a complete system may resemble that shown in Figure 13-1, Web services uniquely among current distributed systems technology allow a great deal of flexibility in the composition of underlying infrastructure. While as developers we may be expected to build secure, mobile, transaction-aware, reconfigurable services, we may equally be expected to produce simply a secure Web service. As we progress through this chapter, remember that each highlighted technology can be taken as a discrete component in its own right, and does not depend on any of the other technologies. That is, we are free to mix-and-match technologies in keeping with the general Web services philosophy, and so each example can be seen as a specific application in its own right and the examples can be taken as a whole composite application.

Developing Enterprise Web Services. An Architect's Guide
Developing Enterprise Web Services: An Architects Guide: An Architects Guide
ISBN: 0131401602
EAN: 2147483647
Year: 2003
Pages: 141

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