This is a proposal for enabling arithmetic computation in OWL-DL ontologies. Please notice that the ongoing effort towards the new OWL 2 W3C standard specification may make this contribution obsolete as there currently is a discussion on how calculations should be embedded in the language specification and on the nature of their interaction with reasoners.

In the meantime, we believe that a partial solution is necessary in order to fill the gap between ontologies and real world applications and to make declaratively evident more knowledge that, otherwise, would have to be coded in procedural terms, decreasing maintainability and re-usability. Our solution allows for computing the values for data type properties based on formulas encoded in their annotations. We have been inspired by many real world cases, for example, in an ontology describing geometric shapes one will likely need means to declare that the perimeter of a polygon is the sum of the length of each of its sides.

The toolkit that we present, however, has some intended limitations whose reason is that it has not been conceived as a candidate standard but rather as an attempt towards the elicitation of the requirements that such standard should have, and a pragmatic partial solution to the problem.