There’s nothing more that architects love to do than argue about definitions. If you ever find yourself with idle time in a room of architects, try asking for a definition of “Service” or “architecture” and see what sort of creative melee you can start. That being said, definitions are indeed very important so that we can have a common language to communicate the intent and benefit of the very things we are trying to convince business to invest in. From that perspective, a number of concepts have emerged in the past decade or so that have become top of mind for self-styled enterprise architects: architecture frameworks and reference architectures. In previous ZapFlashes, we discussed architecture frameworks, which leaves the topic of reference architectures left untouched by ZapThink. Since we can’t leave a good argument behind, we’re going to use this ZapFlash to explore what reference architectures are all about and what value they have to add to the Service-Oriented Architecture (SOA) story.

What is a Reference Architecture?
One commonly accepted definition for reference architecture is that it provides a methodology and/or set of practices and templates that are based on the generalization of a set of successful solutions for a particular category of solutions. Reference architectures provide guidance on how to apply specific patterns and/or practices to solve particular classes of problems. In this way, it serves as a “reference” for the specific architectures that companies will implement to solve their own problems. It is never intended that a reference architecture would be implemented as-is, but rather used either as a point of comparison or as a starting point for individual companies’ architectural efforts.

Others refine the definition of reference architecture as a description of how to build a class of artifacts. These artifacts can be embodied in many forms including design patterns, methodologies, standards, metadata, and documents of all sorts. Long story short, if you need guidance on how to develop a specific architecture based on best practices or authoritative sets of potential artifacts, you should look to a reference architecture that covers the scope of the architecture that you’re looking to build.

One of the most popular examples of reference architectures in IT is the Java Platform Enterprise Edition (Java EE) architecture, which provides a layered reference architecture and templates addressing a range of technology and business issues that have guided many Java-based enterprise systems.

Reference Architectures vs. Architecture Frameworks
While the above definition(s) may seem fairly cut and dried, there is a lot in common between the concepts of reference architectures and architecture frameworks. For some, this is where things get dicey and definitions get blurry. Architecture frameworks, such as the Zachman Framework, the Open Group Architecture Framework (TOGAF), and Department of Defense Architecture Framework (DoDAF) provide approaches to describe and identify necessary inputs to a particular architecture as well as means to describe that architecture. If a particular architecture is a cookbook that provides guidance on how to go about solving a particular set of problems with a particular approach, an architecture framework is a book about how to write cookbooks. So, architecture frameworks give enterprise architects the tools they need to adequately describe and collect requirements, without mandating any specific architecture type. More specifically, architecture frameworks describe an example taxonomy of the kinds of architectural “views” that an architect might consider developing, and why, and provides guidelines for making the choice for developing particular views.

This differs from the above concept of a reference architecture in that a reference architecture goes one step further by accelerating the process for a particular architecture type, helping to identify which architectural approaches will satisfy particular requirements, and figuring out what a minimally acceptable set of architectural artifacts are needed to meet the “best practices” requirements for a particular architecture. To continue our analogy with cookbooks, if an architecture framework is a book on how to write cookbooks, then a reference architecture is a book that provides guidance and best practices on how to write cookbooks focused on weight loss, for example. This would then mean that the particular architecture you develop for your organization would be a specific cookbook that provides weight-loss recipes targeted to your organization. Indeed, if you get puzzled with the definitions, replacing the term “architecture” with “cookbook” is helpful: cookbook frameworks, reference cookbooks, and your particular cookbook.

Furthermore, most reference architectures emphasize the "template" part of the definition of a reference architecture. Both frameworks and RAs provide best practices, and while it might be argued that RAs provide more of a methodology than a framework does, RAs are still not really characterized by their methodology component. Most can be characterized by their template component, however. From this perspective, patterns are instances of templates in this context. In fact, multiple reference architectures for the same domain are allowable and quite useful. Reference architectures can be complementary providing guidance for a single architecture, such as SOA, from multiple viewpoints.

The Value of a SOA Reference Architecture
In many ways, SOA projects are in desperate need of well-thought out reference architectures. ZapThink sees a high degree of variability in SOA projects. Some flourish and succeed while others flounder and fail. Many times the reason for failure can be traced to bad architectural practices, premature infrastructure purchasing, and inadequate governance and management. Other times the failure is primarily organizational. However, what is common in most successes is well-documented and/or communicated architectural practices and a systematic method for learning from one’s mistakes and having a low cost of failure.

Furthermore, we find that many architects spend a significant amount of their time researching, investigating, (re-)defining, contemplating, and arguing architectural decisions. In many cases, these architects are reinventing the wheel as their peers in other companies, or even the same company, have already spent that time and effort defining their own architectural practices. This extra effort is not only inefficient, but also prevents the company from learning from its own experiences and applying that knowledge for increased effectiveness.

From this perspective, SOA reference architectures can provide some help to those struggling with their SOA efforts or thinking about launching a new one. SOA reference architectures allow organizations to learn from other architects’ successes and failures and inherit proven best practices. Reference architectures can provide missing architectural information that can be provided in advance to project team members to enable consistent architectural best practices. In this way, the SOA reference architecture provides a base of assets that SOA efforts can draw from throughout the project lifecycle.

Indeed, in order to gain the promised SOA benefits of reuse, reduced redundancy, reduced cost of integration, and increased visibility and governance, companies need to apply their SOA efforts in a consistent manner. This means more than buying and establishing some vendor’s infrastructure as a corporate standard or adhering to the latest WS-* standards stack. SOA reference architectures can serve as the basis for disparate SOA efforts throughout the organization, even if they use different tools and technologies. Good SOA reference architectures provide SOA best practices and approaches in a vendor-, technology-, and standards-independent way. Therefore, don’t go hunting for one from your favorite vendor of choice. In fact, if you got your SOA reference architecture from that vendor, you might want to consider dropping it in lieu of something more vendor-neutral.

In particular, OASIS offers a SOA Reference Architecture (RA) that “models the abstract architectural elements for a SOA independent of the technologies, protocols, and products that are used to implement a SOA. Some sections of the RA will use common abstracted elements derived from several standards.” Their approach uses the concept of “patterns” to identify different methods and approaches for implementing different parts of the architectural picture. While the OASIS SOA Reference Architecture is certainly not the only valid one on the block, it certainly makes a good starting point for those looking for a vendor-neutral SOA reference architecture on which to base their own architectural efforts.

The ZapThink Take
Enterprise architects needs all the help they can get to make sure that they deliver reliable, agile, resilient, vendor-neutral architectures to their organization that meet the continuously changing requirements of the business. While certainly the art and practice of enterprise architecture continues to mature, companies should look to borrow as much best practices as they can and learn from others who have already gone down the EA and SOA path. If you plan to learn SOA, or any form of EA for that matter, as you go along, or even worse, from a vendor, then you risk the entire success of your SOA efforts. Rather, leverage (for free) SOA reference architectures so that you can advance at a faster pace and lower risk. Bernard of Chartres put it best in the well-known saying: “we are like dwarfs on the shoulders of giants, so that we can see more than they, and things at a greater distance, not by virtue of any sharpness of sight on our part, or any physical distinction, but because we are carried high and raised up by their giant size.” Stand on the shoulders of other enterprise architecture giants and let them increase your vision and success.