RE: URIs / Ontology for Physical Units and Quantities

However, note that ISO 8601 is only for “Gregorian dates, times, datetime intervals, durations, and recurring datetimes.”

So does not support non-Gregorian descriptions of time – such as GPS, Unix time,
also geological, archeological, dynastic, Hebrew, Islamic, Baha’i etc.

(Yeah – I know I keep saying this, but I don’t want us to miss a potential gotcha with ISO 8601 and derived standards like XSD datatypes, which is also inherited by OWL.)

--------

From: Wes Turner [mailto:wes.turner@gmail.com]
Sent: Friday, 8 May 2015 12:49 AM
To: Ralph TQ [Gmail]
Cc: Mark Harrison; Martin Hepp; Kingsley Idehen; W3C Web Schemas Task Force; Paul J. Keller; <steve.ray@sv.cmu.edu>; Jack Hodges; Jack Spivak
Subject: Re: URIs / Ontology for Physical Units and Quantities

Note also that, for durations of time, schema:duration (range schema:Duration) specifies "(use ISO 8601 duration format<http://en.wikipedia.org/wiki/ISO_8601>)."

http://schema.org/Duration

https://wrdrd.com/docs/consulting/knowledge-engineering#iso8601


ISO8601
Wikipedia: https://en.wikipedia.org/wiki/ISO_8601

Standard: http://www.iso.org/iso/iso8601


ISO8601 is a standard for specifying Gregorian dates, times, datetime intervals, durations, and recurring datetimes.

An ISO8601 datetime is specified as: year, month, day, hour, ‘T’ or space, minute, second, timezone.

A Z timezone specifies Universal Coordinated (or “Zulu”) time.

  *   http://www.w3.org/TR/NOTE-datetime


Examples of ISO8601:

2014

2014-10

2014-10-23

20141023

2014-10-23T20:59:30+Z       # UTC / Zulu

2014-10-23T20:59:30Z        # UTC / Zulu

2014-10-23T20:59:30-06:00   # CST

2014-10-23T20:59:30-06      # CST

2014-10-23T20:59:30-05:00   # CDT

2014-10-23T20:59:30-05      # CDT

20

20:59

2059

20:59:30

205930

2014-10-23T20:59:30Z/2014-10-23T21:00:00Z

2014-10-23T20:59:30-05:00/2014-10-23T21:00:00-06

PT1H

PT1M

P1M

P1Y1M1W1DT1H1M1S
Note
AFAIU, ISO8601 does not specify standards for milliseconds, microseconds, nanoseconds, picoseconds, femtoseconds, or attoseconds.

On Thu, May 7, 2015 at 9:43 AM, Wes Turner <wes.turner@gmail.com<mailto:wes.turner@gmail.com>> wrote:
Ralph,

QUDT:

From https://wrdrd.github.io/docs/consulting/knowledge-engineering#qudt

Homepage: http://www.linkedmodel.org/doc/qudt/1.1/

Standard: http://qudt.org/

Namespace: http://qudt.org/schema/qudt#<http://qudt.org/schema/qudt>
xmlns: @prefix qudt: <http://qudt.org/schema/qudt#<http://qudt.org/schema/qudt>> .
LOVLink: http://lov.okfn.org/dataset/lov/vocabs/qudt


QUDT (Quantities, Units, Dimensions, and Types) is an RDF<https://wrdrd.com/docs/consulting/knowledge-engineering#rdf> standard vocabulary for representing physical units.

  *   QUDT is composed of a number of sub-vocabularies
  *   QUDT maintains conversion factors for Metric and Imperial Units

A few JSON-LD examples could be very helpful.


On Thu, May 7, 2015 at 7:21 AM, Ralph TQ [Gmail] <rhodgson@topquadrant.com<mailto:rhodgson@topquadrant.com>> wrote:
Hello Mark,

QUDT is now a non-profit organization with the desire to join W3C to move forward on standardization. The management at NASA has given its approval for QUDT to proceed with this.

Release 2 is a substantial body of work that is finally reaching a publication status. This involves the generation of content with support for LaTeX formatting. Examples can be seen at the following web pages:


  1.  The documentation on the QUDT schema - http://www.linkedmodel.org/doc/2015/DOC_schema-qudt-v2.0

  2.  An example of a LaTeX rendered instance of the Hartree Unit - http://www.linkedmodel.org/doc/2015/hartree

The site www.linkedmodel.org<http://www.linkedmodel.org> has links to documentation for other ontologies and for those that QUDT depends on (VAEM, VOAG and DTYPE).

All the QUDT ontologies are managed on a GitHub site. There is also a WordPress site.

QUDT would welcome participation from others and once we become a member of W3C a working group would be important to establish. Perhaps we should have a discussion on how to get started?

We have long believed that for (some) data to be truly linkable on the web it benefits from being quantified.

I will send another email setting out the remaining work we are doing on the ontologies. In my view the most important of which is standardization of the QNames of the units (e.g, unit:SEC for second, unit:S for Siemen, and unit:KM-PER-SEC not unit:KM-PER-S) so that they are consistently reference-able and conforms with their standard abbreviations . This work is almost complete for SI units.

Regards,

Ralph Hodgson, @ralphtq<http://twitter.com/ralphtq>
TopQuadrant, Inc., www.topquadrant.com<http://www.topquadrant.com/> @TopQuadrant<http://twitter.com/topquadrant>
cell: +1 781-789-1664<tel:%2B1%20781-789-1664> / fax: 703 299-8330<tel:703%20299-8330> / main: 919 300-7945<tel:919%20300-7945>

On May 7, 2015, at 4:56 AM, Mark Harrison <mark.harrison@cantab.net<mailto:mark.harrison@cantab.net>> wrote:

Dear Martin,

I understand your very valid concerns about Linked Data resources that are not supported and maintained and end us wasting time for developers.  However, from this thread it also seems that there is quite some interest in having a well recognised ontology for units of measure in which units have corresponding stable URIs that link to definitions, UN ECE codes, conversion factors and offsets, etc.  QUDT 1.1 made a very good start on this, although it had one or two inaccurate cross-references.  For example, I found within http://qudt.org/vocab/unit#Grain the following nonsensical triple:

<http://qudt.org/vocab/unit#Grain>  skos:exactMatch  <http://dbpedia.org/resource/Cereal> .

There are some other gaps in QUDT 1.1, such as missing resources for units such as milligram, microgram - and because the SI base unit of mass is the kilogram, it is not sufficient to simply define the multipliers such as 'milli', 'micro', because we don't usually talk about milligrams as microkilograms, for example.

Having said that, if QUDT 1.1 were updated, corrected, supported a more complete set of units and provided cross-references to the corresponding UN ECE Common Code values as strings, I think it (or something very like it) could be an extremely valuable resource for everyone, especially because of the conversion factors and offsets.

The QUDT.org<http://QUDT.org> website appears to be last updated in March 2014 and there is some information and a presentation by Ralph Hodgson (copied) about the plans for release 2.0 of QUDT.  However, I'm not sure whether that work has stalled or is under-resourced or is spending a long time in careful internal review.  Maybe those of us who are interested in making this happen could offer to share the workload and accelerate the progress.  In case NASA / TopQuadrant is no longer the place to host it, then perhaps we could reasonably ask W3C to host it in perpetuity and maintain a liaison with the UN, ISO and other relevant bodies to ensure that we're aware of their changes that should be reflected through maintenance updates to such a vocabulary.

We're soon hoping to see much more structured data about products being published openly on the web as linked data, potentially including details about ingredients, nutrition and allergens.  GS1 has already prepared begun drafting a web vocabulary [ see http://www.gs1.org/gtin_plus_public_review ] to help manufacturers and retailers express such information in much richer detail than they can currently using schema.org<http://schema.org> alone - and efforts are underway to harmonise this effort with schema.org<http://schema.org> to make life easier for developers.  I expect that a stable supported ontology with URIs and Linked Data for units of measure along the lines of a QUDT 2.0 could be far more useful to software developers than simply denoting a unit of measure by its UN ECE Common Code string.  We can certainly do better than that.  It could almost certainly avoid a large amount of duplicated effort in coding conversion factors and offsets and would also help to ensure that whether the product specifications are provided in SI units or non-SI units (as they are in different regions of the world), the same quantitative information is readily available so software applications, without ambiguity or unnecessary duplication of effort by developers.

I hope that Ralph Hodgson can chime in with a brief status update on QUDT 2.0 - and also that those of us who would be interested in helping to accelerate this (or something similar) can step forward and offer to help with reviewing it or beta testing it - or filling in the gaps for the missing features.

Best wishes,

- Mark Harrison




On 7 May 2015, at 09:08, martin.hepp@ebusiness-unibw.org<mailto:martin.hepp@ebusiness-unibw.org> wrote:

Dear Kingsley:
Technically, as we agree, this is no big deal.

But there are so many abandoned RDF / Semantic Web efforts rottening on the Web and wasting the time of developers who try to built something on top of it -- until they find out that the project is way out of date -- that I do not see any gain in such a quick fix.

Martin


On 07 May 2015, at 01:25, Kingsley Idehen <kidehen@openlinksw.com<mailto:kidehen@openlinksw.com>> wrote:

On 5/6/15 6:31 PM, martin.hepp@ebusiness-unibw.org<mailto:martin.hepp@ebusiness-unibw.org> wrote:
The problem is not the one time generation. The problems are as follows:

1. Copyright - Are you allowed to republish the code set as RDF?
2. Sustainability - Are you commited to keep the URIs dereferencable, or will some domain grabber take the domain name once the creator has completed his/her PhD and lost interest.
3. Updates - Will you keep the RDF version in sync whenever the standard changes?

Unless there is a clear "yes" to all three questions, it is better to use the official codes than derived URIs.

Martin

Martin,

What's wrong with:

<#someResolvableVariantOfIdentifier>
a owl:Thing ;
dcterms:identifier "{literal-variant-of-standard-identifier}" .

Which can be further embellished by Linked Data publisher in their ontology/vocabulary by adding the following:

dcterms:identifier
a owl:InverseFunctionalProperty .

Productive workflow:

1. Get the data dump in a spreadsheet
2. Save as CSV
3. Load into LOD or Google Refine
4. Map to relevant ontology (existing, or new)
5. Dump data into an RDF document
6. Publish (note: using # as indexical mechanism makes the publication Linked Open Data prinicples compliant off-the bat).


It can be done quite easily. I deliberatly opted not to do it :)


Kingsley



On 06 May 2015, at 23:56, Wes Turner <wes.turner@gmail.com<mailto:wes.turner@gmail.com>> wrote:

How much time do you think it would take to generate RDF (and namespaced URIs) from the linked spreadsheet?

Mappings to/from UN/CEFACT codes (as owl:sameAs mappings to strings) could certainly be useful.

On May 6, 2015 4:31 PM, "martin.hepp@ebusiness-unibw.org<mailto:martin.hepp@ebusiness-unibw.org>" <martin.hepp@ebusiness-unibw.org<mailto:martin.hepp@ebusiness-unibw.org>> wrote:
I think a validator should simply use the list of valid codes from the most recent UN/CEFACT document (available as MS Excel from http://www.unece.org/cefact/codesfortrade/codes_index.html).

There might be unit of measurement ontologies out there that hold the UN/CEFACT Common Code string for a subset of all units as a literal value. But for validation, one should use the authoritative list from the Excel files (since they are updated from time to time).

URIs are not better than strings for validation, because URIs are strings.

Best wishes / Mit freundlichen Grüßen

Martin Hepp

-------------------------------------------------------
martin hepp
e-business & web science research group
universitaet der bundeswehr muenchen

e-mail:  martin.hepp@unibw.de<mailto:martin.hepp@unibw.de>
phone:   +49-(0)89-6004-4217<tel:%2B49-%280%2989-6004-4217>
fax:     +49-(0)89-6004-4620<tel:%2B49-%280%2989-6004-4620>
www:     http://www.unibw.de/ebusiness/ (group)
       http://www.heppnetz.de/ (personal)
skype:   mfhepp
twitter: mfhepp

Check out GoodRelations for E-Commerce on the Web of Linked Data!
=================================================================
* Project Main Page: http://purl.org/goodrelations/





On 06 May 2015, at 20:34, Wes Turner <wes.turner@gmail.com<mailto:wes.turner@gmail.com>> wrote:

Thanks!

I notice that with QUDT there are SI conversion factors and complete URIs for each unit.

Is there a schema for validation of "schema:QuantativeValues supports all UN/CEFACT Common Codes"?

(A similar quandry as with MedicalCode; where URI namespaces (like icd10:) would be more helpful for terminological validation and disambiguation than plain string keys)

On May 6, 2015 4:26 AM, "martin.hepp@ebusiness-unibw.org<mailto:martin.hepp@ebusiness-unibw.org>" <martin.hepp@ebusiness-unibw.org<mailto:martin.hepp@ebusiness-unibw.org>> wrote:
Hi Wes,
sorry for a very late reply:

Actually you could easily use schema:QuantitativeValue for both time and volume, with SEC as the unit code for t and LTR as the unit code for liters, and link both via schema:valueReference, or better, and owl:subProperty thereof.

For the principle, see

   http://wiki.goodrelations-vocabulary.org/Documentation/Structured_values_and_value_references



schema:QuantativeValues supports all UN/CEFACT Common Codes for units, which should cover all you need:


   http://wiki.goodrelations-vocabulary.org/Documentation/UN/CEFACT_Common_Codes


(Mind the full list in the public Excel files, the page just highlights a small subset.)

Best wishes / Mit freundlichen Grüßen

Martin Hepp

-------------------------------------------------------
martin hepp
e-business & web science research group
universitaet der bundeswehr muenchen

e-mail:  martin.hepp@unibw.de<mailto:martin.hepp@unibw.de>
phone:   +49-(0)89-6004-4217<tel:%2B49-%280%2989-6004-4217>
fax:     +49-(0)89-6004-4620<tel:%2B49-%280%2989-6004-4620>
www:     http://www.unibw.de/ebusiness/ (group)
       http://www.heppnetz.de/ (personal)
skype:   mfhepp
twitter: mfhepp

Check out GoodRelations for E-Commerce on the Web of Linked Data!
=================================================================
* Project Main Page: http://purl.org/goodrelations/





On 01 May 2015, at 13:45, ☮ elf Pavlik ☮ <perpetual-tripper@wwelves.org<mailto:perpetual-tripper@wwelves.org>> wrote:

Hi Wes,

On 01/26/2014 07:20 AM, Wes Turner wrote:
Say I am trying to share a tabular dataset. [1] There's metadata for
the Dataset, and there's metadata for the particular columns (which
applies to the particular data items).

For example:

t   volume (liters)
-----------------
1  1
2  0.7
3  0.5
4  0.3
5  0.1

Questions
===========
# Is there (a good) way to specify these units and quantities (in
addition to XSD datatypes)?
You might like to check out
* https://iotdb.org/pub/iot-unit.html


Cheers!



--
Regards,

Kingsley Idehen
Founder & CEO
OpenLink Software
Company Web: http://www.openlinksw.com

Personal Weblog 1: http://kidehen.blogspot.com

Personal Weblog 2: http://www.openlinksw.com/blog/~kidehen

Twitter Profile: https://twitter.com/kidehen

Google+ Profile: https://plus.google.com/+KingsleyIdehen/about

LinkedIn Profile: http://www.linkedin.com/in/kidehen

Personal WebID: http://kingsley.idehen.net/dataspace/person/kidehen#this







--
Wes Turner
https://westurner.org<https://westurner.org/>
https://wrdrd.com/docs/consulting/knowledge-engineering




--
Wes Turner
https://westurner.org<https://westurner.org/>
https://wrdrd.com/docs/consulting/knowledge-engineering