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   RE: [xml-dev] RE: RELAX NG and type derivation [Was:] XQuery andDTD/Sche

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7/8/2002 1:21:58 PM, "Dare Obasanjo" <dareo@microsoft.com> wrote:

>For those out there that may not know what W3C XML Schema was supposed to achieve I suggest looking at the 
requirements from 1999[0] particularly the structures[1] and data types[2] sections
>[0] http://www.w3.org/TR/NOTE-xml-schema-req 
>[1] http://www.w3.org/TR/NOTE-xml-schema-req#Structural
>[2] http://www.w3.org/TR/NOTE-xml-schema-req#Datatype

Hmm, that's an interestingly irreconciliable (in retrospect of course!) set of constraints:

"optimized for interoperability;
simple enough to implement with modest design and runtime resources;

The XML schema language specification shall:

be prepared quickly;
be precise, concise, human-readable, and illustrated with examples."


mechanisms to enable inheritance for element, attribute, and datatype definitions;

provide for primitive data typing, including byte, date, integer, sequence, SQL & Java primitive data types, etc.;
define a type system that is adequate for import/export from database systems (e.g., relational, object, OLAP);
distinguish requirements relating to lexical data representation vs. those governing an underlying information set;
allow creation of user-defined datatypes, such as datatypes that are derived from existing datatypes and which may 
constrain certain of its properties (e.g., range, precision, length, mask)."


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