Article:		Storing XML in Relational Databases
Subject:		Storing XML in Relational Databases
Date:		2003-08-21 06:07:40
From:		Barry Schaeffer
Thanks for the information. I am puzzled, however, by the lack of differentiation between XML that the DB vendors target (flat or message related) and that encountered in document content applications. Oracle states, for example, in its developers guide, "complex XML is difficult to map into a relational model" after which it suggests that any such structures should be handled via CLOBs. This differentiation occurs in other vendors' approaches as well and, if ignored by prospective users, can seriously midlead the direction of XML storage. Indeed, using a RDBMS for anything more than, as Oracle suggests, "using XML to port data into structures already stored in a relational model" (they use a PO as their example) they face a set of potentially serious problems, not the least of which are performance degrades as XML trees become more complex, visibility degrades as valuable XML content is stored in LOBs and cost increases as the user must create software to support import and access, again as the DB vendors illustrate in simple form but which is much more complex in actual practice. An interesting sidenote in your piece might have been some notice of the fact that the software industry is moving toward a native approach to XML, represented by a number of native XML repositories. We use Tamino in much of our work and find the ability to import, manage and query complex XML without mapping it to another model to be quite liberating. There are pros and cons on Tamino itself and on the Software AG approach, but it is representative of an approach that is specifically designed to handle the type of deeply nested, richly tagged XML that we often find in legal, technical and scientific content. There is, I believe, a bright line between interchange use of XML that the RDB vendors seek to support, and content modeling use of XML that they want no part of (the BLOB approach to storage is nearly 15 years old.) Thanks again for the analysis. Regards, Barry Schaeffer CEO X.Systems, Inc.

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• Storing XML in Relational Databases
  2003-08-23 08:17:52 Igor Dayen [Reply]
  
  Thanks for feedback and suggestions very much.
  I agree that the market of native XML databases has been evolved
  substantially for the past couple of years; you may be interested in
  checking Ronald Bourret's product directory
  http://www.rpbourret.com/xml/XMLDatabaseProds.htm for details.
  As it is stated in the reference above, Tamino's powerful import facilities allow
  "individual XML documents to be composed of data from multiple, heterogeneous sources,
  such as the native XML data store, relational databases, and the file system".
  It is also worth to note that XML support in RDBMS incorporates now some
  features attributed to native XML databases. Oracle 9i, for example, introduced
  XMLType, which allows applying XPath expressions and indexes towards XML documents.
  Regards,
  Igor Dayen,
  ObjectCentric Solutions Inc.
  
  
  • Storing XML in Relational Databases
    2004-08-23 23:38:02 query [Reply]
    
    I need to convert Access table into XML format for onward submission to Middleware. Appreciate your urgent help.
    
    
    • Storing XML in Relational Databases
      2004-08-24 19:09:57 Igor Dayen [Reply]
      
      Here are a couple of options you may consider:
      (a) export from Access into flat file
      with further conversion into XML using
      custom-made parsing solution or
      using a vendor tool
      (you may check for CredibleXML, see
      http://www.crediblexml.com/);
      (b) export from Access into MS SQL Server
      and generate XML out of SQL Server table with
      use of FOR XML syntax.
      Igor Dayen