[sc34wg3] Computed values in TMDM

Patrick Durusau sc34wg3@isotopicmaps.org
Mon, 30 Jan 2006 08:29:44 -0500


Going throught the TMDM in hopes of writing the long awaited TMRM -> 
TMDM mapping and I have a question about computed values.

4.1 Introduction says:

"Certain properties in the model are specified as computed properties, 
which means that they are specified in terms of how their values *may* 
be produced from other values in the model." (emphasis added)

Am I correct in assuming that computing the property is purely optional? 
That is that if I wanted to (and I had the necessary information) I 
could simply keyboard the value for any computed property? Or I could 
compute the value?

The reason I ask is that I am trying to decide if "computed property" is 
a constraint that the property value must be computed?

The constraint on the value of the property is clear.

What is unclear is what happens if I keyboard the value in but computing 
the same value would produce a different result? Granted that would be 
an invalid value but I don't see any mechanism to deal with that situation.

The merging procedure for all items appears to presume that the value is 
*always* computed because it does not mention what to do if one or more 
of the values were manually added and differed from each other or ones 
that were computed. That is the item resulting from the merge is going 
to have the computed properties, but which one, assuming there is one 
that is different?

There are only two "computed" properties, [parent] and [roles played]. 
It is easier to see the issue with [roles played] but I don't see why it 
could not also occur with [parent] due to poor keyyyboardinnng.

I grepped the list archives but did not come up with anything useful on 
this issue.

Hope everyone is at the start of a great week!


Patrick Durusau
Chair, V1 - Text Processing: Office and Publishing Systems Interface
Co-Editor, ISO 13250, Topic Maps -- Reference Model
Member, Text Encoding Initiative Board of Directors, 2003-2005

Topic Maps: Human, not artificial, intelligence at work!