Sure, but that has already been done in code. So my question is: “What is the benefit of having a declarative description of the relationship between units?”

So is there some kind of reasoning?

And even if so: I would rather want to see “units” as part of any knowledge model.

Personally, I have been quite happy with UCUM:

http://aurora.regenstrief.org/~ucum/ucum.html

For the inclusion into Topic Maps, I have simply “evolved” the model to include units into it, and also the notation, and of course the query language.

A “native” solution. It was fast and easy to do.

The next post will look at what I think HyTime has got. Then hopefully the one after that will look at how we could make use of what HyTime has got in a Topic Map. I actually think that scope for assignment might be the easiest way to make this work, but doing something with decorating the occurrence type in the ontology to define a default measurement unit for a specific occurrence type might be an interesting way forwards.

@Bob:

QUDT looks like exactly the kind of thing I am thinking about. Probably the only place I would have a quibble (and it is a minor one) is the use of decimal values to express the conversion factors rather than expressing conversion as a ratio of whole numbers. Maybe I don’t have to carry on wading through HyTime :)

@Patrick and Steve

The charter for the OASIS TC looks very promising. Of course, it says nothing about Topic Maps, so perhaps the way forward for this blog is to think about what Lars Marius calls “attachment” (good term) of units to measurements expressed in a topic map. However, I’ve got far enough down the road of reading the right bits of HyTime that I might as well also write up my own findings as well…stay tuned :-)

Plenty to mull over…

Cheers,

- Steve

Excellent! Just excellent!

Err, there is a charter pending for a TC in OASIS that is going to be working on measurement ontologies (although not the sort of mapping you are talking about). Still, it may be of interest: OASIS Quantities and Units of Measure Ontology Standard (QUOMOS) Technical Committee, http://lists.oasis-open.org/archives/tc-announce/200911/msg00013.html.

Where to start? That’s a hard question, particularly given my long time co-editorship with Newcomb. Not sure I read it the same way I would have without that. I am willing to look at it again, this month in fact, to see if i can suggest some likely chunks that avoid some of the added complexity. If nothing else it would be more interesting that some of the other reading that occupies a good bit of my time.

This is both interesting and important, not too often that is seen in any area of endeavor.

Hope you are having a great day!

Patrick

I don’t know if you heard that I’ve joined TopQuadrant last August, but around that time some co-workers convinced NASA to let them publish the measurement units ontology that they developed with NASA. See http://composing-the-semantic-web.blogspot.com/2009/08/units-ontology-with-spin-support.html. I’m sure they’d be very happy to get some feedback on its use.

Bob