The SysML QUDV (Quantities, Units, Dimensions and Values) modelLibrary is specified in a UML/SysML class/block diagram. In order to generalize its potential usage and alignment with other standardization efforts concerning quantities and units, it is of interest to verify that the QUDV model can also be represented in the form of an ontology using a formal ontology definition language.

The QUDV model has successfully been expressed in OWL2 DL (W3C Web Ontology Language v2) using the open source Protégé v4 tool.

The SysML-QUDV ontology is split into two parts (modules):

• SysML-QUDV which contains the basic ontology, i.e. it defines the classes, object properties and data properties. Currently the annotations are incomplete.

• SysML-QUDV-SI which contains the ISQ and SI individuals. The individuals represent some quantities, units, scales and a prefix for the International System of Quantities (ISQ) and International System of Units (SI), as defined in ISO 31 and ISO/IEC 80000. In addition inch is defined to show one non-SI unit with its conversion factor. Dimensions are not represented yet. The QUDV specification in Annex C.5 of the SysML v1.2 spec contains an algorithm in OCL that defines how to derive dimensions for all quantity kinds that are specified in a specific system of quantities.

The full set of XML/OWL and Manchester OWL Syntax source code files and screenshots is available in this ZIP file 2009-10-30-sysml-qudv-in-protege-owl.zip.

SysML-QUDV ontology files in RDF/XML format:

• sysml-qudv.owl, version of 2009-10-30 serialized in RDF/XML

• sysml-qudv-si.owl, version of 2009-10-30 serialized in RDF/XML

Warning: This initial version may well contain some mistakes. It should be regarded as a Proof of Concept.

The screenshots below from Protege provide an overview.

Asserted Class Hierarchy

Inferred Class Hierarchy

Inferred Class Tree by OWLViz

Object Properties

Data Properties

Selection of Individuals representing ISQ and SI