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726Re: [xml-dbms] Re: UPDATE & DELETE

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  • Ronald Bourret
    Mar 2 12:56 PM
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      robin@... wrote:
      >
      > I think Ron's idea of a specification/requirements for UPDATE/DELETE
      > is the only way to go before writing code. That way people have an
      > opportunity to see whether or not the design meets their requirements
      > before waiting to be disappointed.
      >
      > Has a list of requirements/designs been produced (other than Ron's
      > below for delete)?

      You can find more ideas on:

      http://www.rpbourret.com/xmldbms/specs/updates.htm

      I think the biggest question I'm wrestling with now is what the XML
      document used in an update should look like.

      Option 1: The application sends an entire XML document and a set of
      instructions saying what to update, what to delete, what to insert, etc.

      This is relatively easy to implement, but the UI is not clear at all.
      How does the application tell XML-DBMS what has changed? Another problem
      is that there is no easy way to implement optimistic concurrency. That
      is, XML-DBMS has no easy way to decide whether another user has changed
      the data.

      Option 2: The application sends an entire XML document and XML-DBMS does
      a diff between the document and the database and changes the database
      accordingly.

      This is simple for the application, but potentially very difficult to
      implement, especially if sibling order is not maintained. It does allow
      optimistic concurrency.

      Option 3: The application sends document fragments telling XML-DBMS what
      parts of the document to change. (These could be in the form of before
      and after states.)

      This is probably easy to implement, although the UI is not entirely
      clear. It is similar to what database applications do at the moment --
      executing an UPDATE statement only for those columns in a table that
      have changed.

      I am curious to know how people envision update working. That is, what
      do they expect their application to have to do to update the database?

      -- Ron
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