This article is based on the book Open Source SOA scheduled to print January 2009. This article is courtesy of Manning Publications. The ebook is available and sold exclusively through Manning Publications.

The open source community includes many early advocates of the recent wave of emerging SOA-related technology projects. Historically, however, open source has sometimes been considered a "late follower," with commercial products first to hit the market, and then followed by "me-too" open source alternatives. One reason frequently cited by critics of open source is that open source projects are often not innovators, but imitators (of course, some might argue Microsoft has done very well by following the imitation model). There may be some truth to that, but many of the products we'll be examining are very innovative and cutting-edge. In some instances, the reason development has lagged vis-à-vis commercial offerings is simply because of resource challenges - open source projects are often supported and staffed by a very small team of developers, many of whom have full-time responsibilities elsewhere.

Overall, it did take some time before a comprehensive collection of open source projects achieved sufficient breath and maturity as to offer a compelling alternative to the highly priced commercial alternatives. Now, there are many choices for crafting an entirely open source SOA environment. This excerpt forms the basis for the remainder of the book, as it identifies the open source products that we will be examining in greater detail. The selected products will form the basis for our OpenSOA Platform, and I will illustrate how these products can be integrated together in a coherent fashion so that, combined, they will equal or surpass in value the offerings by the commercial SOA vendors. Figure 1 recaps the technologies involved in the OpenSOA Platform and highlights (in double-width lines) those that will be investigated moving forward (as you recall, JMS, Application Servers and GUIs are covered thoroughly by other publications or are fairly commoditized in functionality).

Over the past 5 years I personally have had the opportunity to participate in "real-life" projects that have used many of the open source products discussed here. In choosing which ones will constitute our OpenSOA Platform, I pick "winners" from the competing selection of products. This is not intended to suggest those that are not selected are any less worthy. As with any evaluation process, the final choice is based on some combination of objective and subjective facts (obviously, we all want to believe we only use objective facts, but human nature often dictates against such logic).

Before we dive into each of the technology categories and the open source possibilities within each of them, we'll first try to set to establish some general, universal criteria that we can use when evaluating any of the products.

Open Source Evaluation Criteria
Some general criteria exist for examining all of the technology products that constitute the OpenSOA Platform. They are described in Table 1.

Now that we have identified the general evaluation criteria that we can apply toward evaluating any of the technologies that constitute the OpenSOA Platform, we will now look individually into each technology category and identify for each an open source product that we will use moving forward. In this process, we will identify competing open source solutions and address: 1) the criteria used for evaluating the products within a category; and 2) the justification for why a given product was chosen. We will start with Business Process Management, otherwise popularly known as BPM.