Database vs XML document archive

Discussion in 'XML' started by Hallgeir Stuenes, May 13, 2006.

  1. I'm trying to understand the differences between a XML document archive
    versus a relational data base.

    What are their advantages and disadvantages?



    - Hallgeir
    Hallgeir Stuenes, May 13, 2006
    #1
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  2. Hallgeir Stuenes

    enrique Guest

    I've not looked under the hood of an XML document archive, but from my
    casual reading and my working indirectly with with them:

    * they are not relational databases
    * they do not have support for SQL; "querying" capability is probably
    limited to what the vendor provides in a proprietary API

    I hope someone else will respond to your quest and provide a better
    response than mine.
    enrique, May 13, 2006
    #2
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  3. Hallgeir Stuenes

    Peter Flynn Guest

    enrique wrote:
    > I've not looked under the hood of an XML document archive, but from my
    > casual reading and my working indirectly with with them:
    >
    > * they are not relational databases
    > * they do not have support for SQL; "querying" capability is probably
    > limited to what the vendor provides in a proprietary API


    Leaving aside the confusing issue of what "an archive" actually is,
    I think your second point is unlikely: I would expect any current
    XML storage system that has a search capability to use one of the
    many XML search engines and provide an interface using XQuery. I
    can't think of any good reason why "an XML document archive" would
    need SQL support.

    It is a mistake to expect to be able to use SQL to search information
    which may not be meaningfully put into relational form. If you are
    dealing exclusively with e-commerce data, where your XML is just a
    verbose representation of traditional rectangular data (rows and cols)
    then it is possible to map the features of SQL onto a relational
    data model. But I contend that if your XML information is traditional
    text documents, a relational model is probably not as useful as the
    structural access provided in (for example) XSLT by XPath, and the
    query access provided by XQuery.

    [OP]
    > I'm trying to understand the differences between a XML document archive
    > versus a relational data base.


    An XML document archive is for storing XML documents.
    A relational database is for storing relational data.
    If your XML documents can be normalised to the relational model, or
    if your relational data can be expressed adequately in XML, feel free
    to use either system, otherwise pick the right tool for the job.

    ///Peter
    --
    XML FAQ: http://xml.silmaril.ie/
    Peter Flynn, May 13, 2006
    #3
  4. enrique wrote:
    > * they do not have support for SQL; "querying" capability is probably
    > limited to what the vendor provides in a proprietary API


    XQuery is intended to occupy this sort of role for data stored as an XML
    document or infoset.

    Some recent tools may be able to intermix SQL to explore logical
    relationships and XQuery to explore structure. I *think* the most recent
    release of DB2 can do that, since it's a full relational database with
    an XML infoset datatype rather than only supporting one or the other.


    --
    () ASCII Ribbon Campaign | Joe Kesselman
    /\ Stamp out HTML e-mail! | System architexture and kinetic poetry
    Joe Kesselman, May 13, 2006
    #4
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