[tmcl-wg] FYI: TMSchema presentation updated

[Robert Barta]

On Sat, Mar 27, 2004 at 03:53:27PM -0500, Dmitry wrote:
> I did several changes in TMSchema presentation:

> http://homepage.mac.com/dmitryv/TopicMaps/TMCL/Lite/TMSchemaPresentation/TMSchema.html

Dmitry,

Thanks for adding more text, I think I understand this now a bit
better. Here are my comments:

- You say "TM schema ... can be modelled in TM constructs".

  Is this not true for ANY constraint language, and actually any
  formal language? If I take, say, a Python (brrr :-) program, then

  if False:
     print "Python is cool"
  else:
     print "Oh, well"

  The I can present this as TM construct like

  (if-then-else)
  if-branch   : code-123
  else-branch : code-234

  (is-sequence)
  block: code-123
  statement: print-345

  ...

  This also makes every such language accessible to introspection:

  Give me all if-statements {in AsTMa?}:

  forall $ifs [ (if-then-else) ]
  return

     {$ifs}

- Your external occurrences can be text. Maybe we should restrict them
  to only hold URIs?

- TMSchema is VERY verbose. And it suffers from the same problem as tolog
  in the sense that you cannot keep things together which belong together:


      baseNameSchema (composer, baseName, ....)
      ...
      baseNameSchema (composer, baseName/short, ...)

  I HAVE to separate them into different clauses.

  On the other hand, is there a way to independently express the
  cardinality and other aspects? Say, I want to constrain for basenames
  that

    (a) The value is a string of the form /some pattern/, or
    (b) must be one of 'rumsti', 'ramsti' or 'romsti', or
    (c) must have a particular data type

  And how can I have 2 basenames with the same scope but the same value?

- TMSchema can only capture 'structural constraints', i.e. constraints
  which constrain the form and content of topics and assocs. It cannot
  constrain ontological information. Something like

     'if a company is owned by something that something must be a
     legal entity'

  Is this correct?

- In

     http://homepage.mac.com/dmitryv/TopicMaps/TMCL/Lite/TMSchemaPresentation/img21.html

  you say that constraints should be part of the TM itself?

  I think this is/was not a good idea for XML, so I wonder whether we
  should introduce this dependency into TMCL. I can well imagine that
  one and the same TM document can have several quite distinct TMCL
  constraints. If one of them is somehow attached to the document,
  this would introduce some asymmetry.

- In

     http://homepage.mac.com/dmitryv/TopicMaps/TMCL/Lite/TMSchemaPresentation/img19.html

  you suggest to use 'scope' for inferred information. The problem I
  see is that this mixes the plane of the original content with that
  of a derived one and this usually is asking for trouble.

  The way I see this, is that an ontology O, when it is combined with a
  map M to enrich it

     O + M

  forms a new map. All derived information is in that new map.

  Whether that is now really created in a materialization event (as a
  snapshot):

     M' := O + M

  or whether TMQL works on a 'virtual map' O + M and all the
  inferences are created on the fly may depend on the data and the
  necessary performance.

Let me know what you think.

\rho