David Leal / Ontology Summit Synthesis Panel - 26-Mar URI for quantities, units and scales Motivation  URIs are being assigned to quantities, units and scales  RDF implementations can require this  Different organizations do this when they need to  Consequences  URIs are assigned more than once  URIs are assigned by organizations which do not have particular responsibility for quantities, units and scales  Problems  Which URIs do you use?  The link between the URI and the identified thing is tenuous »The link is probably person readable text that references a normative document issued by BIPM or ISO.  The namespace of the URI does not indicate the authoritative source

David Leal / Ontology Summit Synthesis Panel - 26-Mar URI for quantities, units and scales Do a little better  Organizations with authority (e.g. BIPM and ISO) assign URIs  There may still be other URIs  The URIs assigned by BIPM or ISO will be the obvious ones to use  The namespace of the URI leads to the right organization  Parse the URI to find the relevant document (e.g. ISO URN)  Dereferencing the URI to get information about the relevant document (or the relevant document itself)  ISO 1000 defines symbols (Greek and Latin characters) to identify units in person readable documents  “The Web” is becoming a domain of equivalent importance, therefore the authoritative standards should also address it by assigning URIs. This is nothing to do with ontologies yet.

David Leal / Ontology Summit Synthesis Panel - 26-Mar URI for quantities, units and scales Some formal statements  A core ontology?  “The metre” is a member of the quantity space “length”. »Is this true? Is the term “quantity space” correct? What is its definition?  Is this stated in the authoritative standard using a formal language (e.g. OWL)? »Is length an owl:Class?  Rapidly get into deeper water  “The Kelvin” is a member of the quantity space “temperature.” »Is this true?  “ITS90” is a monotonic increasing function with domain “temperature” and range “the reals”. »Is this true? How do we record the relationship to Kelvin and to “IPTS68”. These topics are within the domain of the metrology experts.

David Leal / Ontology Summit Synthesis Panel - 26-Mar URI for quantities, units and scales Building on the foundations  Symbols for quantities, units and scales  Derived units, prefixes, etc.  Person readable text in current ISO standards  Much work already done in UnitsML  RDF/OWL version using BIPM/ISO URIs »an annex to ISO standards? »use of MathML vs UnitsML for mathematical expressions  Outside SI »The definition of mm is computer interpretable in an ISO standard, with reference to the URI for the metre, so...  The definition of international inch and US survey inch is computer interpretable in an ANSI standard »Same type of representation - a task for NIST?  Dimensional analysis

David Leal / Ontology Summit Synthesis Panel - 26-Mar URI for quantities, units and scales What next? 1. Establish the principle  If you create a standard in engineering or commerce, assigning URIs to the things defined by the standard (whether formally or in person readable text) is your task – not somebody else’s. »It is just like assigning a symbol in Greek and Latin characters. 2. Work with the authoritative sources to include formal statements based upon the URIs in the standards  Today BIPM and ISO TC12 do their stuff, and web people do different stuff (UnitsML, etc.)  The advance of technology means that the communities have to come together 3. A standard for how to define derived units  Based on UnitsML, MathML etc.  Implementations in XML Schema and RDF/OWL  Perhaps a harvesting + development task for ISO TC184/TC12 JWG