Taxonomy is a method used to classify entities, items, and categories, among other things. The ultimate goal of taxonomy is to establish a hierarchy or structure of categories (in our case, all SOA artifacts). In this sense, an ontology is a wider concept because it is primarily responsible for the identification, separation, and description of categories, and it is further used in our classification to establish relations. Ontology is closer to the theory of classification, originally defined by Aristotle as the first philosophy. Recall that that's where we started in the first chapter—the identification of frameworks, principles, and characteristics essential for our service-oriented architecture. Finally, we put them together and declared relations and dependencies.

Now, we extend this initial hierarchy with the essential SOA elements to maintain optimal composability as an immediate target and promote effective SOA Governance. The outcome will...