Who Serves Your Ontology?

When you have an ontology, you have to choose whether to present it yourself, or via one or more third-party repositories. There are good reasons to do it either way, as described below. Additional considerations are described in the section on Registering and Accessing Ontologies.

A significant consideration is that ontologies that are published on the Web can be harvested by various registries, thereby providing some of the advanced services that working through a registry can provide. This is discussed further in the Summary below.

Serving An Ontology Yourself

Advantages to self-publishing include simplicity, control, speed, and namespace identity. Any or all of these gains may be sufficiently important to overcome the advantages offered by an organized publication service.

Publishing an ontology can be as simple as making a document called {someName}.owl available on the Web. This solution maximizes simplicity, control, and speed for the ontology provider, since making a file available on the Web is trivial for even casual Web publishers. The entire publication process is within the control of the provider.

A second strategic value of self-publishing is that the Uniform Resource Identifiers (URIs) associated with the ontology resource, and its terms, can be local to the provider and resolved at the provider's website. So, for example, the provider can declare that the namespace of the ontology—the string used as a prefix for the terms in the ontology—can be in the provider's domain, such as http://mywebsite.com/ontologies/.

With this namespace arrangement, all the term identifiers will be visible from the provider's domain, and the provider can decide how to respond if someone enters one of those terms into a Web browser or ontology tool. This provides a complete level of control over the entire user experience with the ontology.

Serving An Ontology Through a Third Party

A complementary set of advantages are obtained by letting an ontology provider serve your ontology. Both organizational and technical strength is offered by most of these ontology hosts, since they have to serve multiple ontologies. At the same time, the field is so new that each provider often provides a relatively unique set of services, so the value may be diffuse depending on exactly what services you are looking for.

The most visible value offered by an ontology repository is the services (functionality) built in to the repository. These services run from basic to advanced:

  • storage and backup
  • registration and Web visibility, with association with other similar ontologies
  • tools to ensure the ontology is viable and follows good practices
  • tools and services to analyze, search, cross-reference, and track usage of your ontologies
  • metadata guidance, entry, and maintenance
  • human and online advice on ontology creation
  • automatic URI generation
  • automatic URI resolution (dereferencing)

The last two services above require more discussion. An ontology's terms should be at least named on the Web, by creating labels for each term resource. These labels can be a Uniform Resource Identifier (URI) in any form—a Web address, a Uniform Resource Name (URN), a Universal Unique Identification (UUID), or a number of other forms. The author or publisher of the ontology should declare the URI that is associated with each term to avoid ambiguity about the identifier. (Multiple identifiers for a single semantic resource is generally A Bad Thing.)

Another nice feature is to provide a Uniform Resource Locator, or URL, a Web address at which more information about the term can be obtained. While it is not necessary that the URL and the resource URI be the same—some experts even discourage this practice—there are significant social advantages to using the same string for both purposes. If you want to achieve this social purpose, it means implementing some additional capabilities to name and resolve the ontology terms you have created.

An ontology service can offer social value as well. By providing organizational stability and permanence, the service provides preservation for your ontology over time, which may not be possible with your local Web server and organization. And by archiving old versions of the ontology and making them available and comparable, and ontology repository preserves the history of your work.

Registering Through a Third Party

A third approach is registering your ontology with an ontology registry, while continuing to serve the document yourself. This is similar to registering your Web pages with search engines. It can be a suitable middle ground to achieve your goals, if the services provided by the ontology registry complement the services you are capable of providing. Further discussion of this is available in the next section.


If you are doing very basic ontologies for your own use, or the use of a narrow community, publishing it yourself with minimal services is a reasonable tradeoff. If you have obtained a basic review of the ontology you are publishing, it should be possible to make a useful asset publicly available with fairly limited resources.

On the other hand, if your ontology is at all likely to be a community resource, you need to be aware of the value that can be added by using community services. By considering which capabilities are important to your needs (and, ideally, which capabilities will provide the most community advantage), you can often increase the value of your ontology both for yourself and for a large collection of other users. These improvements can often be achieved with very little additional effort and can save significant effort later.

Suggested Citation

Graybeal, J. 2011. "Who Serves Your Ontology?." In The MMI Guides: Navigating the World of Marine Metadata. http://marinemetadata.org/guides/vocabs/ont/provider/servingontologies. Accessed July 9, 2020.