Re: [xml-dev] Why Multipath (LCA) Hierarchical Query Processing Work

[mike@adatinc.com]

Joe Celko's and the other hierarchical processing solutions you mentioned is to use external programmable hierarchical programming functions and they also do not handle the necessary multiple node type and multiple data occurences necessary for XML. Using the Left Out Join in a hierarhical data modeling fashion allows full multipath hierarchical processing to be transparently performed automatically and correctly including nonlinear multipath queries. See my DevX ANSI SQL Hierarchical Processing article at: http://www.devx.com/xml/Article/39183/1954

 

            /Mike 

-----Original Message-----
From: Peter Hunsberger [mailto:peter.hunsberger@gmail.com]
Sent: Monday, August 3, 2009 12:08 AM
To: mike@adatinc.com
Cc: XML-dev@lists.xml.org
Subject: Re: [xml-dev] Why Multipath (LCA) Hierarchical Query Processing Works Automatically in ANSI SQL

On Sun, Aug 2, 2009 at 10:25 PM, wrote: > Basic ANSI SQL inherent hierarchical processing using the Left Outer Join to > model and processes hierarchical structures is basically quite obvious and > empirical and I have covered this in my previous SQL/XML articles. The proof > for multipath hierarchical query processing which requires Lowest Common > Ancestor (LCA) processing occurring naturally in ANSI SQL is not that > obvious because it is truly quite amazing since it was never designed into > ANSI SQL and is quite complex to perform. Empirically it can be proven from > its results, but it would be very nice to know how and why it is working so > we can absolutely trust the results. I have written an article describing > the how and why of natural LCA processing in ANSI SQL and have appropriately > entitled it “The Ghost in the Machine”. It can be located below. > > The Ghost in the Machine > http://www.tdan.com/view-articles/11069 > > This LCA processing in XQuery is not automatically performed today and is > too complex to do with procedural navigation. This problem has been > researched academically and attempted solutions use LCA functions that have > to be inserted correctly by the query user which takes away for its ease of > use and schema-free purpose. My work with LCA processing has shown that LCA > processing can involve nesting LCA’s that I do not necessarily see occurring > in this LCA XQuery research limiting their future solutions to more simple > queries. ANSI SQL performing LCA processing automatically has no multi-path > LCA query limitations. This has been referred to a LCA query processing, at > least three decades ago. Mike, Perhaps I'm missing something here, surely you're not really suggesting that we should code outer joins to manage hierarchical structures in a relational database? Why not just use Celkos set / subset tree management (or other related algorithms)? We've got some tree structures several 1000 nodes deep and wide managed in a relational database, can you me exactly how you would go about finding (for example) all the leaf nodes for such a tree? -- Peter Hunsberger _______________________________________________________________________ XML-DEV is a publicly archived, unmoderated list hosted by OASIS to support XML implementation and development. To minimize spam in the archives, you must subscribe before posting. [Un]Subscribe/change address: http://www.oasis-open.org/mlmanage/ Or unsubscribe: xml-dev-unsubscribe@lists.xml.org subscribe: xml-dev-subscribe@lists.xml.org List archive: http://lists.xml.org/archives/xml-dev/ List Guidelines: http://www.oasis-open.org/maillists/guidelines.php