Re: [xtm-wg] Summary of PM discussion

[Lars Marius Garshol <larsga@garshol.priv.no>]

* Sam Hunting
| 
| I've tried to put all the ideas I've read on the PM into a
| high-level summary as follows.
 
Thank you very much for this, Sam! I think it was the right step at
the right time. I wanted to do it myself, but had no bandwidth.

The next step is perhaps for the participants in the debate to state
their current positions, so that we can see if we need to discuss this
any further, or whether we are sufficiently close to consensus that we
can just make a decision and move forward.

| Some of the ideas might not need to be here -- the community should
| be the judge. Probably the best feedback for this would be a more
| completely thought-through version, rather than a lot of small
| criticisms.

I don't think that would be useful yet. I could do it, but I think it
not be very useful unless people could say what they meant about it so
that we knew where we stood. We need discussion in order to reach
consensus, and that has to take the form of lots of pinpricks.  I'll
try to be as high-level and brief as I can, though.

Anything I don't comment on you can just assume I agree with.

The ASR (which I think Nikita called Application-Specific
Representation) is to me the same as the DM, and so can be taken
out. If anyone thinks this is wrong I can probably be convinced.

 
| No.   Name Data model  Notation               comment
| ---   ---- ----------- ---------------------- ---------------
| [3]   DM   graph       prose (SRN)            Published(DC)
|            OO          UML (Luis)             Published(4)
|            OO          UML (Eliot)            Post-Paris(3)
|            grove       property set           Mentioned               
|            graph       unknown (chercheurs)   Forthcoming
|            N.A.        prose (Lars)(2)        Published(5)
|            ??          EXPRESS (Eliot)        Mentioned

Of these, my preferences are, in this order:

 - infoset-based
 - EXPRESS
 - UML
 - property sets/groves

The graph approaches I think would serve our purposes so badly that I
would go to great lengths to avoid them.

You left out the RDF (Martin Lacher) and topic map (Geir Ove)
approaches. On these I am agnostic.
 
| (There is also an expressed preference by some developers for
| a node/properties approach, but no proposal yet. It's possible
| that groves would satisfy this preference.)

The UML, EXPRESS, infoset and groves approaches are all
node/properties approaches.
 
| Another expressed concern is that the notation proposed may bias the
| data model. For example, UML is by definition an OO approach, yet
| systems that must manage topic maps that are terabytes in size may
| not want the overhead of objects.

This concern is quite simply misplaced. The conformance part of the
specification just needs to make it clear that implementors are not
required to follow the approach used in the specification as long as
they include all the information.
 
| On the other hand, if the notation and the data model truly are
| orthogonal, then UML could be used to create a graph data model.

All the approaches could.
 
| >From angle brackets to data model
| ---------------------------------
| Then there is the question of how close ("isomorphic") the data
| model should be to the XTM syntax. How this would affect the
| notation chosen is not clear.

I don't think it would at all, and I think this is a separate
discussion. I think the time to go into it is after the notation has
been chosen.
 
| Fear and loathing 
| -----------------       
| Finally there are various visceral likes and dislikes.
| Some find nodes and arcs loathsome; others break out in
| hives at the thought of UML diagrams; these feelings must
| all be worked through in the course of the next month.

I agree, and this is why I think it would be useful if participants
were to state their current positions (as I did above), so that we can
see where we are. If there is something that is acceptable to everyone
(or nearly so) we can just pick that and move on. We need to get this
discussion over and done with as soon as we can.
 
--Lars M.


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