--- /dev/null
+* some notes on the relation of XML and ISIS
+
+
+XML is in widespread use as a lingua franca
+for glueing software components together.
+Several tools for this can be found at xml.apache.org.
+
+What is missing here is an efficient, easy to use
+way of storing XML data. Only the most trivial cases
+are easily mapped onto the relational data model,
+which uses flat records, consisting of a fixed number
+of fields. The data structures modelled in XML
+typically have a variable number of childs.
+Hierarchical databases like ADABAS C are well suited
+and actually used by SoftwareAG in their Tamino XML DB,
+but aren't widely and freely available.
+
+
+* ISIS to XML
+
+ISIS records can be easily and canonically converted to XML.
+Anything up to the first subfield delimiter is the body (a text node),
+subfields are attributes
+(strictly XML-ish this is ok only for non-repeated subfields).
+Other special subdivisions of field content like the typical
+<key word> may split to real child nodes.
+
+The result (as generated by make pdemo) may look like:
+$
+<isisrec id="148">
+ <v69>
+ <key>Educational Psychology</key>
+ <key>universities</key>
+ <key>Kenya</key>
+ </v69>
+ <v70>Okatcha, F.M.M.O.</v70>
+ <v30 a="1 p."/>
+ <v24>Personal statement</v24>
+ <v26 c="1976"/>
+ <v12 p="Tbilisi, USSR" d="1976">Symposium on the Psychological Bases of Programmed Learning </v12>
+</isisrec>
+$
+
+Instead of tag numbers and subfield characters,
+symbolic names from the FDT may be used.
+
+
+* XML to ISIS
+
+XML data structures can be
+easily and efficiently mapped to the data model of ISO2709.
+
+The general conversion (based on a SAX parser) works as follows:
+- when encountering an opening tag, look up it's name in the FDT.
+ If there is no FDT provided, create one on the fly.
+ If the FDT does not contain the tag name,
+ create a new entry using tag number max(100,1+highest tag in FDT).
+ Create a field using the tag number found and field value '+'.
+- when encountering an attribute, look up it's name in the
+> Meta metadata
+ Create a new subfield entry if needed using code 'a'
+ or 1+highest code used (for this tag).
+ Append a subfield using the code found.
+- When encountering an empty tag (the current field ends with />),
+ change the starting '+' to '-'.
+- When encountering a text node, add a field using tag number 0
+ with the node's body as value.
+- When encountering a closing tag, look up it's name as for opening tags,
+ add a field with an empty value.
+- As additional optimization, most text nodes can be eliminated
+ by using the initial value of a node to represent an immediatly
+ following text node.
+
+For example look at RDF (
+> http://www.w3.org/RDF
+,
+> http://archive.dstc.edu.au/RDU/reports/RDF-Idiot
+).
+A structure like
+$
+<DC:Creator parseType="Resource">
+<vCard:FN> Dr Jacky J Crystal </vCard:FN>
+<vCard:TITLE> Director </vCard:TITLE>
+<vCard:EMAIL> jacky@dstc.com.au </vCard:EMAIL>
+<vCard:ROLE> Researcher </vCard:ROLE>
+</DC:Creator>
+$
+canonically maps to
+$
+100 +^aResource
+101 +
+0 Dr Jacky J Crystal
+101
+102 +
+...
+$
+or, with text-node elimination, to
+$
+100 +^aResource
+101 -Dr Jacky J Crystal
+102 -Director
+...
+100
+$
+using about half the bytes it takes to store the original.
+
+If they had made an attribute what can be an attribute
+(not substructered, not repeatable) instead of a child,
+it would read (with explicitly assigned subfield codes)
+much more efficiently like
+$
+100 ^pResource^fDr Jacky J Crystal^tDirector^ejacky@dstc.com.au^rResearcher
+$
+
+Also see
+> unirec
+and
+> Struct
+
+---
+ $Id: xmlisis.txt,v 1.7 2003/06/23 14:43:42 kripke Exp $
projects / webpac / blobdiff