[tmcl-wg] Feedback on TMCL requirements / use cases

[Marc de Graauw]

Hi Mary, Erica,

I went through the TMCL Requirements and Use Cases and I miss constraints on
uniqueness of topic characteristics within a type. Use cases:

- each topic of type 'person' must have an occurrence of occurrence type
'social security number' which is unique (within topics of this topic type)
- each topic of type 'company' must either have an occurrence of type
'homepage'  which is unique (within topics of this topic type) or no
occurrence of type 'homepage'
- each association of type 'marriage' must have a unique combination of
'husband' and 'wife' roleplayers (within this association type).

Sort of the restated TNC for occurrences and associations.

Further, constraints can be merged. I noted that there is no guarantee,
given the current requirements, that Topic Maps after merging still satisfy
the constraints they satisfied before merging. Take for instance
cardinality: if two Topic Maps T1 and T2 both have as a constraint that
topics of type 'person' may not have more than 2 names (2-name-constraint),
and T1 contains a topic with 2 names: 'Mary' and 'mnishikawa', and T2
contains a topic also with two names 'Mary' and 'Mary Nishikawa', then if
those topics merge (due to a shared subject indicator) the resulting topic
will have three names and the resulting topic map will violate the
2-name-constraint. This is more a remark, I guess TMCL & merging will yield
plenty of though nuts to crack.

Marc