What are schemata
Sean Mc grath
digitome at iol.ie
Sun May 31 12:22:53 BST 1998
>* Tim Bray
>| I kind of think that the thing people have in mind in this group
>| when they say "schema" is "expressions of syntactic constraints
>| which can be verified mechanically" or some such.
>* James K. Tauber
>| So is a schema a function that maps a document to a truth value?
[Lars Marius Garshol]
>I'd rather say that it is a definition of a set of documents, just as
>a formal language is usually considered to be the set of sentences
>that are well-formed in that language.
>The software that verifies a document could be called "a function that
>maps a document to a truth value", though. Mathematically, such
>software would perform an "element of"-test on the set of documents
>defined by the schema.
To my mind, a schema is an assertion about the structure of a unit
of data. Parsing w.r.t. to a schema both tests the veracity of the
assertion and generates a "view" of the data as an abstract
Any single piece of data can simultaneously be valid w.r.t. many
different schema. To test different assertions (and generate
alternate abstract data structures) parse w.r.t. a different schema.
Maybe this is what makes me uneasy about "<!DOCTYPE" in an instance.
Data binding itself to one particular schema...
Sean Mc Grath
+353 96 47391
"Me a pedant? That depends on what you mean by 'pedant'".
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