Chapter Nineteen. Leveraging Ontologies and Application Integration

It's a judgment call as to the proper placement of this chapter in the book. It clearly could go with our earlier discussion of metadata. However, this is a fairly new topic in the context of application integration indeed, an advanced topic. Thus, here is where it stays.

Truth be told, ontologies are nothing new, and the use of ontologies within the notion of application integration is nothing new either, no matter if we called it ontology or something different. However, the recognition that ontologies play a major role in the logical understanding of the problem domain if not the solutions, as well is something new. If we understand the ontologies, then we clearly understand how to solve the information integration problem by turning very different schemas and data structures into views and mappings that are more meaningful to both end users and application integration architects.

If you don't understand application semantics simply put, the meaning of data then you have no hope of creating the proper application integration solution. You must understand the data to define the proper integration flows and transformation scenarios, and provide service-oriented (such as Web services) frameworks to your application integration domain, meaning levels of abstraction.

This is where many application integration projects fall down. Most application integration occurs at the information level. So, you must always deal with semantics and how to describe semantics relative to a multitude of information systems. There is also a need to formalize this process, putting some additional methodology and technology behind the management of metadata, as well as the relationships therein.

To this end, many in the world of application integration have begun to adopt the notion of ontology (or the instances of ontology: ontologies). Ontology is a term borrowed from philosophy that refers to the science of describing the kinds of entities in the world and how they are related. Ontologies are important to application integration solutions because they provide a shared and common understanding of data (and, in some cases, services and processes) that exists within an application integration problem domain, and how to facilitate communication between people and information systems. By leveraging this concept we can organize and share enterprise information, as well as manage content and knowledge, which allows better interoperability and integration of inter- and intracompany information systems. We can also layer common ontologies within verticals, or domains with repeatable patterns.

The view of ontologies was best summarized by Quine, who claimed that the question ontology asks can be stated in three words: "What is there?" and the answer is, "Everything."^[1] In the context of information-oriented integration, each information system is regarded as a "theory" that recognizes the existence of a set of objects: its own ontology.

^[1] Quine, W.V. 1948. "On What is There." In "Review of Metaphysics," Vol. II, No. 5; reprinted in From a Logical Point of View (1961).

At its essence, ontology is a conceptual information model.^[2] Ontologies describe things that exist in a problem domain. This includes properties, concepts, and rules and how they relate to one another, which supports a standard reference model for information integration (the link to application integration), as well as knowledge sharing. We leverage ontologies in the science of application integration because they support human understanding of information. This use is self-explanatory within the context of application integration. Ontologies also provide the ability to facilitate information-based access and information integration across very different information systems. We achieve this by formalizing the application semantics between intra- and interorganizational information resources.

^[2] Akkerman. January 15, 2001. "What are Ontologies? An Executive Summary."