In the Net-Centric Data Strategy (NCDS), a community of interest (COI) is defined as a collaborative group of users who must exchange information in pursuit of their shared goals, interests, missions, or business processes and who therefore must have a shared vocabulary for the information they exchange. Shared semantics – a common understanding of terms – is an essential part of COIs in the NCDS.

It is therefore ironic that the people concerned with the NCDS do not have a single common understanding of the term “community of interest”. Instead, we find the following four definitions of “COI” in widespread use. (We don’t claim these are “good” definitions, and we don’t propose to make any of them “official”. We only say that when you hear somebody else mention COI in a conversation, they probably have one of these four definitions in mind.)

· Stovepipe COI: An existing functional community with a large, established, and detailed community vocabulary. That vocabulary is completely optimized for their view of the world. They aren’t much interested in any possible overlap with other communities and other views of the world. When forced to share outside the COI, their typical reaction is, “we’ll extend our model, and then you can adopt it”. Some people think that every COI is a stovepipe COI – so if you use the term, they assume that’s what you’re talking about.

· Vocabulary COI: A community that has (or will develop) a common vocabulary for some subject-area domain of interest. As a result, they are able to exchange information, regardless of whether they all actually do exchange with each other. The level of detail and rigor in the common vocabulary will match the COI’s purpose; it could be a dictionary, or a taxonomy, or an implementation-level data model. Some vocabularies will be broad and shallow; i.e. containing a few definitions which can be used by almost everyone. Some vocabularies will be narrow and deep; i.e., with many definitions used by a few people. (Broad and deep vocabularies would be lovely, but are typically too expensive to develop.)

· Sharing COI: A community that actually is exchanging information with each other. This depends on a common vocabulary, and so a sharing COI is always a subset of a vocabulary COI. It also requires data producers who create and post the shared information. It requires some form of shared information space from which consumers pull the data they need. A sharing COI exists at the intersection of these three elements. (I used to call these “operational COIs”.)

· Proponent COI: A community that seeks to establish new or improved information sharing capabilities, often through their influence over acquisition. Typically these aren’t the people who actually share the operational data. They often aren’t the people who develop and learn a common vocabulary. Instead, they collaborate to identify the desired capabilities, and direct (or influence) their own organization to implement the necessary change. These COIs serve as a catalyst for transformation.

This explanation serves as an aid to communication. It’s easier to figure out what someone means by “COI” when you know about the most common possible meanings.