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Putting Web Services into (Business) Context

Putting Web Services into (Business) Context

Web services tool vendors frequently compete on how quickly their users can "generate a Web service from scratch" or "expose a Java/COM+/CORBA class as a Web service." While speed of development is important, the broader business needs of an enterprise must be the main driver of new technology adoption.

Blindly applying new technology ultimately results in more poorly conceived software. These applications are just as difficult to maintain as existing applications, only they're running on yet another technical infrastructure. As ZapThink, LLC, an XML- and Web services-focused industry analyst group, explains, "Just because a new technology has promise doesn't guarantee that it will be applied correctly."

So how do IT organizations move from "playing" with Web services development to providing truly useful services that support key business objectives? Companies must be able to view their existing software development assets (SDAs) within the context of the enterprise's strategic business processes in order to take full advantage of the promise of Web services. IT executives need to understand what assets exist, where they are located, and how each fits into the corporate business landscape, i.e. a model-based approach. This approach to Web services development gives enterprises an efficient way to enable existing SDAs as Web services; it can be broken into four steps - assess, build, locate, and employ.

Let's take a simple example - a currency conversion component - through this process.

Example Component - CurrencyExchange EJB
Our example component is an EJB that provides currency conversion services - converting dollars to euros, setting up conversion tables, and so on. Figure 1 presents this example component in UML, showing the external interfaces of the component without any of the implementation details involved in building the component.

 

The functional capabilities of this component are presented to its users via a SessionBean interface containing a number of method definitions. These methods place dependencies on two supporting elements of the external component definition: a set of transfer object types used to interchange nonprimitive data with the component, and a specialized exception that users of the component must handle when setting exchange rates into the component. Also, our CurrencyExchange component allows its users to control the conversion algorithm or algorithms used when converting one currency to another, both through a component configuration interface as well as by allowing the configured conversion strategy to be selectively overridden on a call-by-call basis.

Applying the enABLE Methodology
The four steps in our model-based approach are:

  • Assess what you have and create a business roadmap for migrating to Web services
  • Build a catalog of essential software development assets (SDAs) mapped to your business roadmap (i.e., your business architectures and models)
  • Locate the most appropriate software assets for your high-priority services using the catalog you have built
  • Employ these assets in your tools of choice for developing Web services

    Assess
    A typical IT organization will have thousands of assets that have accumulated over the years. Assessing which of these assets are of value to the organization moving forward must incorporate both business and technical perspectives. Issues that need to be taken into account during the assessment phase include:

  • The technology used to build the asset
  • Compatibility of the asset's technology with future technical architectures being defined by the organization
  • Level of documentation (i.e., artifacts resulting from the software development process) available that describes the asset's business functionality
  • Current use of the asset to support the organization's business activities
  • Expected use of the asset to support future business needs

    As you begin, remember the 80/20 rule; some SDAs are obvious candidates for your initial cataloging efforts, while other marginal assets are best left behind.

    How does our example component fit against our assessment criteria?

  • Technology: Built using J2EE technology.
  • Future technical architectures: Our organization is in the process of defining a service-oriented architecture that includes Web services as a core element. These Web services will be implemented using a combination of J2EE component technology and adapter technology, which encapsulates legacy applications within our environment.
  • Level of documentation: Component artifacts include source code, a deployable .jar file, a UML model of the component that includes both an external client-oriented view as well as an internal design-oriented view, and javadoc.
  • Current use of asset: Component was built as part of a project to incorporate international capabilities into our order management application.
  • Expected use of asset: As our business expands its international capabilities, the need for a currency conversion service available to multiple departments has become clear.

    Based on our assessment, it appears that our currency conversion component is an important asset that should be preserved and managed into the future. This leads us to the next stage of our model-based approach.

    Build
    In the build phase, our task is to align our essential SDAs with our business roadmap (i.e., our business architectures and models describing current and future business requirements to be placed on the IT organization). The end result of this effort is a ready reference that gives us the ability to see what aspects of our business architecture are already supported, to identify redundancies, and to see where gaps exist. Ultimately, effective use of this reference model will enable us to build Web services that present the right level of information and interact with the right underlying business systems.

    Our business architecture team has been busy defining requirements for our next generation of e-commerce systems, and they have taken the next step to express these requirements in the form of a UML reference model. Figure 2 illustrates a portion of that model that is pertinent to our example component.

     

    Each class within this UML diagram represents a coarse-grained reference component that supports one or more interfaces. If we look into the Currency Exchange System component in more detail, we see that its two interfaces define a series of operations as shown in Figure 3.

     

    The operations defined here can be mapped against the methods defined by our EJB (see Table 1).

     

    Notice that some of our reference component methods are not directly supported by our EJB, and also that some of the capabilities of our EJB (e.g., our ability to configure conversion strategies) aren't reflected in our reference model. However, our mapping does show that we have a strong affinity between our desired business capabilities and this existing SDA.

    Locate
    As our development team is tasked to build out portions of our next-generation business architecture, they will take advantage of our previously built business reference model to search for candidate SDAs that can help them do their work more efficiently. Let's assume that our team has the responsibility to build out a Web service supporting currency conversion. Their work activities flow as follows:
    1.   They begin their work by identifying the portion of the business reference model that applies to their project - specifically, the Currency Exchange System.
    2.   They then investigate the services and operations defined by that reference component.
    3.   For the set of selected operations, they initiate a search against the underlying SDAs mapped against the reference model. In this case, they discover our CurrencyExchange EJB.
    4.   The team then retrieves various artifacts as part of their evaluation process, ultimately concluding that they can take advantage of this asset in their Web services development project.

    How will they investigate the components and services associated with this model? While some groups have built reference models to asset mappings through spreadsheets and other similar tools, an SDA mapping and discovery engine can speed and improve this process dramatically.

    Depending upon the area of the model being investigated, our team might find multiple assets that support a set of business capabilities, at which point they need to determine if they should select one of these assets for future development or if they need to provide an encapsulation service that binds all of the existing assets together and ensures consistent data and behavior across them (if, for example, multiple customer information systems must be supported because of business merger activity in the past). Or they might discover that no existing assets support a portion of our model, indicating that "green-field" development is needed to support some expanded business capabilities. Regardless of the outcome, our team has a better view of what is available to them to use in the next stage of the process.

    Employ
    The employ stage is where all of today's "whiz-bang" Web services tooling comes into play. With our Currency Exchange example, we will likely retrieve our EJB .jar file from its repository location and deposit it into a project within our IDE of choice, then use that IDE's Web service-generation capabilities to convert our SessionBean interface into a Web service with an associated WSDL file, Java client proxy, and other artifacts.

    As part of the employ phase, we have some decisions to make:

  • How should we expose the information from our specialized date range exception to our Web service client?
  • Do we choose to expose our conversion strategy capability on the Web service?
  • Do we create separate Web services for our currency conversion operations from our currency maintenance operations, or do we combine them into one service?

    Ultimately, as these newly built Web services are created and deployed, our team will complete the life cycle by feeding them back into their catalog, mapped against the business roadmap for which they were built. These Web services now become part of the developer's everyday toolkit - resulting in faster, higher quality, less expensive application development and integration.

    Summary
    Taking the time to put our Web services and the underlying SDAs that already exist in our infrastructure into an IT library will ensure that the services we produce will provide true value to the business and not introduce more technology for technology's sake.

    References

  • Schmelzer, R., and Bloomberg, J. ZapFlash, "Understanding the Real Costs of Integration": www.zapthink.com/flashes/10232002Flash.html
  • Alur, Crupi, and Malks. (2001) Core J2EE Patterns; Best Practices and Design Strategies, p. 261. (Prentice Hall PTR).
  • Gamma, Helm, Johnson, and Vlissides. (1994) Design Patterns: Elements of Object-Oriented Software, p. 315. Addison-Wesley.
  • More Stories By Brent Carlson

    Brent Carlson is vice president of technology and cofounder of LogicLibrary, a provider of software development asset (SDA) management tools. He is the coauthor of two books: San Francisco Design Patterns: Blueprints for Business Software (with James Carey and Tim Graser) and Framework Process Patterns: Lessons Learned Developing Application Frameworks (with James Carey). He also holds 16 software patents, with eight more currently under evaluation.

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