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Roger L. Costello wrote:
> Does this indicate that Approach #2 is superior? Is entropy a way to
> measure the value (quality) of Schemas? /Roger
The problem with measuring entropy by schema is like that of measuring
entropy by the shortest program that can produce a given string. If
someone devises a shorter program or a more explicit schema, then the
entropy decreases. In this case, it's straightforward to construct a
more explicit schema that restricts the RDF document as much as the
other schema restricts the XML document:
<element name="Object">
<complexType>
<element name="hasA">
<complexType>
<simpleContent base="string">
<attribute name="property" type="xsd:string"
fixed="Name"/>
</simpleContent>
</complexType>
</element>
<element name="hasA">
<complexType>
<simpleContent base="string">
<attribute name="property" type="xsd:string"
fixed="HairColor"/>
</simpleContent>
</complexType>
</element>
<element name="hasA">
<complexType>
<simpleContent base="string">
<attribute name="property" type="xsd:string"
fixed="SSN"/>
</simpleContent>
</complexType>
</element>
<element name="hasA">
<complexType>
<simpleContent base="string">
<attribute name="property" type="xsd:string"
fixed="Height"/>
</simpleContent>
</complexType>
</element>
<element name="hasA">
<complexType>
<simpleContent base="string">
<attribute name="property" type="xsd:string"
fixed="Weight"/>
</simpleContent>
</complexType>
</element>
</complexType>
</element>
I would claim that if it's possible to write XSLT stylesheets that
losslessly convert between two formats in both directions, then the two
formats are isomorphic and the entropy does not change from an instance
document in one format to the instance document in the other format.
--
Elliotte Rusty Harold elharo@metalab.unc.edu
XML in a Nutshell 3rd Edition Just Published!
http://www.cafeconleche.org/books/xian3/
http://www.amazon.com/exec/obidos/ISBN=0596007647/cafeaulaitA/ref=nosim
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