Query Languages for XML

[Jonathan Robie]

I'm not sure whether I understand the range of things that will be queried.
I would think that we would want to be able to do queries of at least the
following kinds:

1. Queries of non-markup data, with the goal of creating mark-up from
databases, e.g. relational or object-oriented databases. The end result is
to return a grove, but there's a lot that has to be defined in-between.

2. Full-text searches which return groves.

3. Structured document queries which return groves. There's an interesting
discussion of queries that need to be supported here:
"http://www.ceth.rutgers.edu/programs/TEI97/SESSIONS/GREGORY/search.sgm.html"

Standard database query languages like OQL and SQL are not very useful for
queries of type 3 unless we know the actual names of the data structures
used in a particular implementation. For instance, in a relational database,
what are the names of the tables and columns that must be used to create a
query for a given document structure?

Standard database query languages like OQL and SQL do not have full-text
search operators to allow them to do queries of type 2, though some people
have defined full-text operators as extensions of such languages. When it
comes to the return type for such a query, we have the same problem
mentioned in the previous paragraph.

I don't know much about SDQL. It is part of the DSSSL standard - is it
scheme based? Is it procedural? Is it based on SGML/XML document structure?
Can it be used for queries of types 1 and 2?

Jonathan



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