[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] RE: hierarchical XML in a relational DB structure - moving nod
You are close to reinventing tumblers. http://en.wikipedia.org/wiki/Tumblers I built a system like this some years ago in Visual Basic. It is long gone, but I recall that walking in was easy and walking out wasn't. If you delete a branch, reordering was nasty. There was some ugly string and substring handling. I also found it useful to keep the namespace names and GIs in the table in case I wanted to search on GI values because I was keeping multiple documents in the tables and generating multiple document types from the information. After awhile it becomes clear that it is better to use tables as tables and not to store trees as piece parts (ok as blobs or varchars). It comes down to the why of building it but it is fairly easy to build a tree on output from a table but not so nice to store it in a table. In the SGML days, there was a relational guru whose name I can't recall. He was a strong advocate of relational document storage and published some examples in ye Olde SGML TAG mag. After a while, the approach began to break down possibly because this was in the days before namespaces. Charles Goldfarb also published some papers on why this approach has deficiencies. len From: Robert Koberg [mailto:rob@k...] Hi, I want to use a relational database to store data that is nested and where the order is preserved. I am having a hard time wrapping my head around how to do the following mostly because I don't have much experience with relational databases. I am looking at mapping a structure like so: <node id="1"> <node id="11"> <node id="111"> <node id="1111"/> <node id="1112"/> <node id="1113"/> </node> <node id="112"/> <node id="113"/> <node id="114"/> </node> <node id="12"> <node id="121"/> <node id="122"/> <node id="123"/> </node> </node> To a relational database that might have a table representing it like: Node ------- id parentId parentIndexPosition First question: Is using an index position the best way to maintain the position? (or is preceding and/or following sibling better? or something else?) OK, lets say I have imported some data/XML into the above table, giving appropriate parents and index positions. Next, say I want to move /node/node[2]/node[@id=121] to the position /node/node[1]/node[1]. How do you handle updating the index position of other nodes? All children of /node/node[@id=12] will need their parentIndexPosition moved down one. And all children of /node/node[@id=11] will need their parentIndexPosition moved up one. (the ID attributes where abritrarily created and should not indicate position) Is there a built in mechanism to do this type of thing in relational databases? If not how would an UPDATE look? Are there any java libraries or articles out there that handle this type of thing? (I am having a hard time finding anything with google) thanks, -Rob ----------------------------------------------------------------- The xml-dev list is sponsored by XML.org <http://www.xml.org>, an initiative of OASIS <http://www.oasis-open.org> The list archives are at http://lists.xml.org/archives/xml-dev/ To subscribe or unsubscribe from this list use the subscription manager: <http://www.oasis-open.org/mlmanage/index.php>
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