3.1. From QUDV to an OML metrology vocabulary🔗

OMG SysML 1.2 introduced QUDV (Quantities, Units, Dimensions, Values) as a library for declaring quantity kinds, units, and their dimensional factoring; QUDV's foundations were then revised substantially across SysML 1.3 and 1.4.

In parallel, a formalization in OML — leveraging the semantics of OWL2-DL for classification-based reasoning — reworked those foundations, the quantity-kind and unit stereotypes carried by SysML, to align them with Dybkær's An Ontology on Property. That effort became the opencaesar metrology vocabulary, whose current version combines the updates and motivations of the VIM4 2nd Committee Draft (2CD, 2023-07-31) with Dybkær's ontological grounding. OWL2 (SROIQ) carries the metrology taxonomy well: specialization, the general-vs-individual quantity distinction (encoded as concept vs. instance), dimensional factoring, and OWL2-DL/SPARQL consistency checks over units.

Where a description logic stops is visible in that vocabulary's own dimensional analysis: computing a derived quantity's dimension from its factors is an arithmetic induction that has to be pushed out of OWL2 into SPARQL 1.1 Update, and even there it is brittle — updates report success while inserting no triples, because "update succeeded" is not a statement about what was established. Dimension arithmetic sits right at that boundary; the kind interaction algebra and the algebraic laws are past it.