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Re: [xml-dbms] A basic question about XML-DBMS

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  • Ronald Bourret
    ... DOMToDBMS supports updates and inserts. DBMSDelete supports deletes. DBMSToDOM supports selects. That should cover everything. ... Can you explain further?
    Message 1 of 6 , Aug 28, 2002
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      Dongling Ding wrote:
      >
      > I will look at DOMToDBMS and DBMSToDOM. But the reason
      > for me to look at XML-DBMS is that it can support more
      > types of actions comparing to others.

      DOMToDBMS supports updates and inserts. DBMSDelete supports deletes.
      DBMSToDOM supports selects. That should cover everything.

      > I still think XML-DBMS can combine some of properties
      > files together and have better structure to be
      > understood.

      Can you explain further? Note that part of the problem with v2 right now
      is lack of documentation, which will be written before the final
      release.

      -- Ron
    • Dongling Ding
      ... The first thing I can think of is to combine action and filter xml files together. In that case users only need to manage one file instead of two.
      Message 2 of 6 , Aug 28, 2002
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        > > I still think XML-DBMS can combine some of
        > properties
        > > files together and have better structure to be
        > > understood.
        >
        > Can you explain further? Note that part of the
        > problem with v2 right now
        > is lack of documentation, which will be written
        > before the final
        > release.
        >

        The first thing I can think of is to combine action
        and filter xml files together. In that case users only
        need to manage one file instead of two.

        Currently, the map file in XML-DBMS is DTD type. Do we
        have a plan to move into XML schema compliant?

        Dongling


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      • Ronald Bourret
        ... I disagree here. Actions and filters are largely separate, so there seems to be little advantage in combining them. Actions are used by DOMToDBMS and
        Message 3 of 6 , Aug 29, 2002
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          Dongling Ding wrote:
          > The first thing I can think of is to combine action
          > and filter xml files together. In that case users only
          > need to manage one file instead of two.

          I disagree here. Actions and filters are largely separate, so there
          seems to be little advantage in combining them. Actions are used by
          DOMToDBMS and DBMSDelete for inserts, updates, and deletes. Filters are
          used by DBMSDelete and DBMSToDOM for controlling what data is deleted /
          retrieved.

          It would be possible to combine map documents and filters. The map
          document is equivalent to join clauses in an SQL statement and the
          filter document is equivalent to WHERE clauses. The advantage of this is
          that it would probably be a lot clearer (I find filter files very ugly).
          The disadvantage (and why I didn't do this) is that it would mean a lot
          of duplicated information. For example, if you wanted two different
          filters over the same set of data, all the map information would be
          duplicated.

          The real solution is to ditch maps, filters, and actions completely and
          write an XQuery engine over JDBC. Don't count on this any time soon :)

          > Currently, the map file in XML-DBMS is DTD type. Do we
          > have a plan to move into XML schema compliant?

          I'm not sure what you mean by "DTD type".

          1) If you mean that the map is validated by a DTD, then there is no plan
          to change to an XML schema, as the DTD provides everything we need. You
          can certainly do this yourself, as there are certainly tools to generate
          an XML schema from a DTD.

          2) If you mean that there is a way to generate maps from DTDs but not
          from schemas, then there are plans to do this. Another user wrote a
          MapFactory_W3CSchema class, but it works with an early version of 2.0
          and I don't currently have time to update it.

          3) Version 2.0 maps were designed with XML Schemas in mind and support
          many of the constructs from XML Schemas. For example, the UseClassMap
          element is designed to support complex types and the TokenList attribute
          is designed to support enumerated types. The main feature of XML Schemas
          that is not supported is inheritance of complex types. I had planned to
          do this, but ran into technical difficulties.

          -- Ron
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