Monday, December 3, 2007

New interesting book on WS-BPEL

I recently read a new Packt book titled "SOA and WS-BPEL: Composing Service-Oriented Solutions with PHP and ActiveBPEL" by Yuli Vasiliev. I've used ActiveBPEL in the past, and there certainly is a learning curve involved in learning BPEL. However, Yuli does an excellent job of explaining both the fundamentals of BPEL, and more advanced BPEL topics such as parallel vs. sequential processing. The use of a ongoing case study walks the user logically through the learning process.

The first section of the book, which I found particularly useful given my lack of PHP experience, primarily focuses on how to consume and build SOAP web services with PHP. Using PHP with SOAP doesn't seem as straightforward as it should be, but Yuli does a good job at describing the process and best practices. The remaining sections cover BPEL, and ActiveBPEL's implementation of them.

The book is fairly brief in size (280 pages), but covers a lot of material in an effective fashion. I would recommend it to anyone interested in using PHP with SOAP and/or ActiveBPEL (the BPEL portions are beneficial even if you are not a PHP developer).


Saturday, December 1, 2007

SOA Essentials, Part 1

A Service Oriented Architecture, or SOA, represents an approach towards software development that emphasizes the creation of reusable software services that are based upon discrete units of business functionality. An example of such functionality might be a software component that can be used for creating a new contact within a customer relationship management (CRM) system. It qualifies as discrete if it can be invoked in a stand-alone fashion by a variety of external applications without undue dependencies on the CRM system. To be considered a truly reusable “service”, it must exhibit certain characteristics, such as a well-defined interface or contract along with a standards-based means of invocation. Once a collection of such services becomes available they, in turn, can then wired together to create new business processes and applications.

For instance, let’s assume Acme Company, as a disciple of SOA, and has created a multitude of such services, including CRM functionality such as creating contacts; inquires/cases; email correspondence; action items and the like. Now, in an effort to improve and streamline lead generation they want to develop a new web-based form so that anyone interested in their products or services can easily place an inquiry. The previous form would only send the inquiry details to an email distribution list that was poorly monitored and tracked. Further, they prospects information would have to be re-keyed into the CRM system manually, which was very tedious (what I call “swivel-chair integration”). With the new inquiry form, they want to use their SOA services to automatically perform the following business process:
  • Create a new Contact in their CRM system.
  • Create a new CRM “Case” using the data provided within the form and assign that Case to an appropriate sales team member (perhaps based on geographic business rules).
  • Create a new “Activity” for the sales team member, which is analogous to a to-do item to follow-up on the inquiry.
  • Automatically generate a response email to the prospect with their Case # and sales team member.
  • Create an entry in their internal Training Management System (TMS) so that the prospect is automatically notified of any upcoming webinars or seminars.
  • Create an event into their Business Activity Monitoring (BAM) system, which is carefully monitored by company executives as part of their Key Performance Indicators (KPI).
In this fictitious example, there are three different enterprise systems that are involved: CRM, TMS and BAM. Fortunately, Acme has already developed service for each of the functions identified, and so they can easily create a new application that incorporates the desired business process. Figure 1 depicts the how the reusable business services, which draw on the enterprise applications, can be used to construct a new, integrated business process. The result of Acne’s new process is improved lead generation, productivity, and response time.

Figure 1

Since Acme has developed a repository of reusable services, they can now respond quickly to market forces by creating new application and processes in a fraction of the time otherwise required in absence of an SOA.

SOA, being the latest in a string of IT “silver bullets, has been subject to a lot of misuse and bastardization. In part, this is due to the eagerness of vendors to associate their products with this new architecture style. Many of the common definitions of SOA do share important characteristic:

“Contemporary SOA represents an open, agile extensible, federated, composable architecture comprised of autonomous, QoS-capable, vendor diverse, interoperable, discoverable, and potentially reusable services, implemented as Web services” (Erl, Service Oriented Architecture, 2005, pg 54).

“Service-Oriented Architecture is an IT strategy that organizes the discrete functions contained in enterprise applications into interoperable, standards-based services that can be combined and reused quickly to meet business needs.” (Domain Model for SOA: Realizing the Business Benefit of Service-Oriented Architecture. BEA White Paper. 2005)

As you can see, the common theme is obviously the notion of discrete, reusable business services that can be used to construct new and novel business processes or applications. The history of IT is replete, however, with component-based frameworks that attempted similar objectives. They include Common Object Request Broker Architecture, or CORBA, along with Microsoft’s Distribute Component Object Model (DCOM) and Java’s Enterprise Java Beans (EJB). What distinguishes these approaches from the newer SOA? There are several:

  • CORBA, EJB and DCOM are all based on remote-procedure call (RPC) technologies. This created tight dependencies between the client application and the underlying RPC components. The RPC components were, by nature, very narrow in scope and usually tailored specifically for use by a single application, thus limiting reusability. Also, RPC solutions tended to generate significant network traffic, and suffered from complications in transaction management (i.e., two-phase commits etc).
  • In the case of EJB and DCOM, they are both tied to specific platforms and were thus not interoperable. Unless a homogenous environment existed (rare in today’s enterprises, which are often grown through acquisition), the benefits from them could not be easily achieved. SOA-based web services were designed with interoperability in mind.
  • Complexity.CORBA, EJB,and to a lesser degree DCOM, were complicated technologies that often required commercial products to implement. SOA can be introduced using a multitude of off-the-shelf, open-source technologies.
  • SOA relies upon XML as the underlying data representation, unlike the others which used proprietary, binary-based objects. XML’s popularity is undeniable, in part because it is easy to understand and generate.

Another distinction between an SOA and earlier component-based technologies is that an SOA is more than technology per se, but also constitutes a set of principles or guidelines. This includes notions such as governance, service-level agreements; meta-data definitions, and registries. These topics will be addressed in greater detail in the sections that follow.

So what does an SOA resemble conceptually? Figure 1.1 depicts the interplay between the backend systems, exposed services, and orchestrated business processes.

Figure 1.1

As you can see, service components represent the layer atop the enterprise business systems/applications. These components allow the layers above to interact with these systems. The composite services layer represents more course-grained services that are comprised from two or more individual components. For example, a “createPO” composite service may include integrating finer-grained services such as “createCustomer”, “createPOHeader”, and “createPOLineItems”. The composite services,, in turn, can then be called by higher-level orchestrations, such as one for processing orders placed through a web site.


Although we’ve already touched on a few of the inherit benefits of an SOA, we can summarize the major benefits as:

  • Business Agility. Business functions, exposed as services, can be stitched together to create new applications using orchestration and workflow products. This allows for rapid creation of new business processes and the ability to quickly alter existing ones. Today’s fast-moving business environment demands such agility in order for companies to remain competitive.
  • Code Reuse. The ability to effectively reuse existing functionality constitutes a cost savings. Perhaps equally significant is the impact on quality. Reusing proven and well-tested assets inevitably improves quality.
  • Platform Agnostic. Services exposed in a standards-based fashion can bridge between differing platforms and languages. For example, a “getCustomer” service written in Java can now be accessed by a .NET client. The popularity of new interpreted scripting languages such as Ruby and Groovy further intensifies the relevance of having agnostic-based services. This also reduces vendor lock-in and switching costs, and encourages true “best-of-breed” adoption.
  • Legacy Enablement. The investment in legacy applications can be preserved by exposing their business rules and functions through service wrappers. This not only saves money, but opens these systems up for more creative purposes. Thus, integration costs are reduced.
  • Standardized XML Vocabularies. The XML-centric nature of SOA encourages the development of a common set of well-defined business object documents. By creating a common vocabulary within your enterprise, integration becomes vastly simplified.

Fundamentally, an SOA is about exposing services that facilitate the sharing of information across application and business boundaries. In our example earlier describing Acme Corporation’s new web inquiry form (figure 1), we demonstrated a business process that spanned across several enterprise systems. This is a common requirement and enables the rapid creation or modification of business processes. This translates into faster turnaround time for the introduction of new products; cost savings derived from greater productivity and efficiency; and faster response to changes in market conditions.

The benefits of moving to an SOA are real, but how can they be realized? The next article will cover what elements are necessary to succeed with an SOA.

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