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Subject: FW: A question re: using XML validation for ensuring proper unitsused in instance document
I’m forwarding this reply to the OASIS UnitsML list.
I forgot to mention that only TC members can use the OASIS list; you can use the comment list, but that only sends the message to the secretary and chair of the TC.
I very much appreciate your reply and offer to join the teleconference and would like to listen in so that I can better formulate the next round of email. That is, I would prefer not to directly make remarks/questions because I'm concerned I would disrupt the meeting from its original agenda, but feel that the context I may get from the meeting will help better communicate via email afterwards.
Also, I am going to the IDEAlliance XML-in-Practice Conference in Arlington, VA on Sept 30. If a representative of the TC is also attending, it may be useful to meet and talk there.
Sorry that I didn’t reply sooner. I’ve copied the OASIS UnitsML TC members with my reply because others in the TC are more familiar with implementing UntisML; I’m more on the development side. Here are my comments on this issue:
1) For those developers who wanted to restrict their users to a specific list of units, we always anticipated that a custom “database” as you describe would be maintained by the developers. This “database” could be incorporated into every XML file, or it could maintained separately at a fixed URL.
2) We’re in the process of developing a Units Database (UnitsDB) which will eventually include code lists provided by various communities that are “linked” to units that are in UnitsDB. E.g., if the military uses “KM” for kilometer, then we would maintain a list of all the military codes for various units and it would include the code “KM” linked to the unit km in UnitsDB. A user could then request all of the military units output in UnitsML. There is an element in the UnitsML Schema that allows for providing the code value for the unit in a specific code list. Conceivably, we could also output the code value as the unique identifier for each unit; or the user could make that substitution.
3) Unless there is a great demand for it, we cannot guarantee that UnitsDB would be available 24/7, which is why we would expect that developers would maintain their own “database.” However, NIST does have experience with providing networked time data on a 24/7 basis to the financial community, so we would consider providing that service for UnitsDB if we thought it was essential to our user communities.
4) Regarding your question below, I don’t have a definitive answer (others on the TC might provide more input). I’ve attached a sample XML output from UnitsDB. For each unit, there is at least one QuantityReference available that could be used to guarantee that a user, for example, only uses the unit meter to designate a length and not a weight.
We’re having a teleconference TC meeting tomorrow. Ordinarily only TC members are allowed to participate in the TC meetings. However, if you wanted to attend this meeting and make a few remarks or ask a few questions, I would allow that. If it seems that the conversation is extensive, we may need to set up a separate teleconference meeting to address this issue, or we may be able to handle it through email messages.
Details for the TC meeting:
The next UnitsML TC teleconference meeting is at 10:00am – 12:00 noon EDT Wednesday, Sept 16, 2009.
Toll Free: 888-946-7619
I hope you find this information to be useful.
Robert A. Dragoset, physicist
Chair of the OASIS UnitsML Technical Committee
My group at Pitney Bowes is investigating how best to use unitsML for descriptions of mail items. We are building an XML schema that represents the physical dimensions of a mail item, including width, height, thickness, weight, etc. One of the things we want the schema to ensure is that those who use the schema use one of a set of proper units for a given dimension, e.g., length dimensions can be in, cm, m, yd but not lb or oz.
Our approach for this is to create our own units "database," i.e., an instance document that conforms to unitsML that uses a pattern for the identifiers of the units. This way, we can use standard XML validation for ensuring that appropriate units are used. For example, the identifier for a specified inch unit is "distance-in" and one for a cm unit is "distance-cm." We create specialized measurement types that restrict the identifiers used in a unit attributes to the pattern. This approach means, as far as we can tell, that we will need to always have our own "database."
Question: is there a better way in unitsML where we can use the XML validation feature to ensure that the proper units (i.e., one from a set) are used for a given quantity? If not, is there a way that we could have a "sameAs" description (URL/IRI and units identifier) in the UnitType (e.g.) where we could connect our description of a unit to your standard description of a unit, and so enable applications to leverage information, like conversions, etc, that look to be a part of a bigger and more complete database?