Relational Tables and structured documents

Michael Kay M.H.Kay at
Mon Mar 23 10:28:18 GMT 1998

Peter Murray-Rust:

>I have been spending the last two weeks working on a molecular application
>which essentially consists of relational tables.  The application is
>largely hierarchical (a protein molecule) so that it benefits from being
>recast into structured document form. I have therefore found it useful to
>create routines which generate nodes in a tree as a result of joining

I think there are several things that one could usefully do.

(1) define a recommended way of representing a relational table in XML.
are a number of ways of doing this, the biggest decision is whether to use a
standard DTD for all tables or a DTD that reflects the specific table

(2) extend this to a richer data model, e.g. the nested relational model,
allows you to represent hierarchic structures, or the ODMG model which
to to represent arbitrary graphs. (Note that the problem then becomes
analogous to the one of using XML as a serialisation format for CORBA

(3) provide a toolkit that allows you to perform transformations on these
documents that reflect the operators of the relevant data model, e.g.
selection, projection, and join; sorting and grouping; flattening of nested
Of course one way to implement such operations would be to load the data
a database, but many of the operations can be implemented directly without
much effort.

I think the key thing is to keep the set of structures and operations very
base it on a data model with an established formal basis rather than
something new.

Mike Kay, ICL

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