Re: [xtm-wg] Equivalence between TM,RDF,Conceptual Graphs?

["Thomas B. Passin" <tpassin@home.com>]

[Danny Ayers]


>
> I don't quite understand... you'd have a type something like
> "INT+VARCHAR(10)" ???
>
Think of a row as being like a struct in C or a record in Pascal - there are
a number of slots, each slot may have a different type.  The struct itself
can be thought of as a type.  A row instance would be like an instance of a
record or struct.

As I re-read your original post, I see you are more thinking of the metadata
rather than the data, so I may have been adding confusion in my response.  I
was thinking more of capturing actual row data in the TM.  Still, metadata
queries are likely to return row data, too, so the principles may be the
same.

By metadata, do you mean basically the database schema?  I'd at least as
interested in the view and query definitions, since they are how you can get
data into or out of a database.  In a proper database application, all
access to the data is through predefined queries.  So the right metadata
would seem to be the returned data types for each query, or the data type
you need to feed to an update query (I'm using "type" in my previous sense
as the type of a row).

It seems to me that if you put such a row type definition into a TM
association, and each member of the association refered to a topic that
described its data type, perhaps using xml-schema data types,  you'd be in a
good position to define classes or whatever from the TM.

To be complete, you'd really want to figure out how to capture the integrity
constraints.  That may be impossible in general, since there can be stored
procedures that get triggered by inserts, deletes, etc, and you probably
can't get and understand those in an automated way.  But at least the
standard relational integrity constraints (from the foreign key definitions)
would be important.

Cheers,

Tom P


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