Naming Conventions and Namespaces

Since ontologies are often shared within and between organizations, it makes sense to consider naming conventions before you start. It is very easy for two or more people to think of different ways of naming properties that may mean little to the other ontology modelers. The more time spent at the planning stage, the less time is likely to be spent working out problems with the ontologies at a later date.

The following is a list of suggested basic conventions for ontology objects based on the naming conventions of RDFS and OWL:

• For class names, use initial capitals (for example, Activity)
• Use lowercase letters for properties (for example, impacts or part)
• Within names, avoid using separators or spaces, but begin all new words with a capital letter (aka camel-case, for example functionOf, InformationResource)
• Names of ontology objects can not have spaces or slashes, but commas, dashes and many other characters are permitted. Define a standard naming convention for your modeling effort that describes which characters are allowed and what should serve as replacements for disallowed characters.

The use of XML Bases

In TopBraid Composer and other OWL tools, the namespace for an ontology is defined by the xml:base or # baseURI statement present in the file. Composer will maintain this automatically, but files created with other tools may follow different conventions or have an invalid syntax. If your ontology, does not contain any baseURI statement, you will see a red exclamation sign next to its name in the Project Explorer. When you try to open such ontology, you will get a message saying that the model is missing an baseURI statement. You will be then given an opportunity to add baseURI statement on-the-fly.

If your ontology does not contain any owl:Ontology resource, Composer will add one at load time.

The use of Namespaces

In addition to the base, you can have other namespaces identified in the ontology. At minimum, you will have namespace statements for RDF, RDFS and OWL. You can also have a namespace statement for any of the ontologies that your ontology imports. Namespaces usually end with either # or /. We do not recommend the use of a default namespace anywhere, because it may lead to confusion once you are working with more complex models consisting of multiple subgraphs.

Related Topics

How to work with imported ontologies

Imports View