http://www.sinica.edu.tw/~ricko/notation.htm
XML Notation Schemas
Rick Jelliffe
1999-06-26
This note is for discussion purposes by the W3C Schema Working Group. It provides an alternative characterization of the schema problem. This provides a framework for addressing many issues not handled in the first working draft of the XML Schema specification.
Definitions
schema:
A structured group of declarations of the notations and their refinements used by document objects in a particular document type definition.
declarations:
Declarations are the formal expression of some information about a group of document objects: in particular declarations define rules over various domains, associate external identifiers with the terminals an non-terminals of the grammars, define and name lexical tokens and higher-level structures, and provide mechanism for analysing, designing, deploying and explaining the information.
document type definition (DTD):
Not to be confused with "XML markup declarations". A document type definition is a set of schemas, which may use different notations, together with informally expressed information.
notations:
A notation is a name given to the grammar used for a fragment of a document. Notations are layered and interwoven through a document: the various levels of character encoding are notation layers, XML is an notation kayer, the additional requirements of XHTML on XML are notation layers, an ECMAScript script in an XHTML document is another notation layer, a BIN64 encoded fragment of text inside that script is yet a further notation. It can be seen that an XML document has a tree of notations, which follows the element and entity structures.
refinements:
Any notation layer can be refined, to constrain the notation further. A notation cannot be relaxed without running the risk of breaking software which relies on the original definition of the notation. Extensible software is software written so that refinements of lower layer notations will not cause the notation-handlers of higher-layers to break.
document objects:
Document objects are defined in DOM. The combination of the document objects and the schema objects makes up the information set of the implementation of a markup language.
Criteria
XML Schemas should be able to provide enough information to allow:
an application to know whether it can accept documents conforming to that schema (e.g., a MIME browser);
a generator to create documents conforming to that schema (e.g., a structured editor);
an application to test a document to see that it does in fact conform to the schema it says it does (e.g. a validator);
an application to restructure a document into the form required by a schema system (e.g. to convert data to RDF);
an application to use the data (e.g. a hypertext application).
As for general test cases for XML Schema:
it can describe XHTML;
it can describe RDF;
it can describe itself;
it can describe hypertext;
it can describe simple database records (I follow XML Schema: datatypes);
it can describe literature (I follow XML markup declarations).
Furthermore, XML Schemas must provide a framework for maximum extensibility, to allow vendors to compete on depth and quality of coverage.
...
XML Notation Schemas
Rick Jelliffe
1999-06-26
This note is for discussion purposes by the W3C Schema Working Group. It provides an alternative characterization of the schema problem. This provides a framework for addressing many issues not handled in the first working draft of the XML Schema specification.
Definitions
schema:
A structured group of declarations of the notations and their refinements used by document objects in a particular document type definition.
declarations:
Declarations are the formal expression of some information about a group of document objects: in particular declarations define rules over various domains, associate external identifiers with the terminals an non-terminals of the grammars, define and name lexical tokens and higher-level structures, and provide mechanism for analysing, designing, deploying and explaining the information.
document type definition (DTD):
Not to be confused with "XML markup declarations". A document type definition is a set of schemas, which may use different notations, together with informally expressed information.
notations:
A notation is a name given to the grammar used for a fragment of a document. Notations are layered and interwoven through a document: the various levels of character encoding are notation layers, XML is an notation kayer, the additional requirements of XHTML on XML are notation layers, an ECMAScript script in an XHTML document is another notation layer, a BIN64 encoded fragment of text inside that script is yet a further notation. It can be seen that an XML document has a tree of notations, which follows the element and entity structures.
refinements:
Any notation layer can be refined, to constrain the notation further. A notation cannot be relaxed without running the risk of breaking software which relies on the original definition of the notation. Extensible software is software written so that refinements of lower layer notations will not cause the notation-handlers of higher-layers to break.
document objects:
Document objects are defined in DOM. The combination of the document objects and the schema objects makes up the information set of the implementation of a markup language.
Criteria
XML Schemas should be able to provide enough information to allow:
an application to know whether it can accept documents conforming to that schema (e.g., a MIME browser);
a generator to create documents conforming to that schema (e.g., a structured editor);
an application to test a document to see that it does in fact conform to the schema it says it does (e.g. a validator);
an application to restructure a document into the form required by a schema system (e.g. to convert data to RDF);
an application to use the data (e.g. a hypertext application).
As for general test cases for XML Schema:
it can describe XHTML;
it can describe RDF;
it can describe itself;
it can describe hypertext;
it can describe simple database records (I follow XML Schema: datatypes);
it can describe literature (I follow XML markup declarations).
Furthermore, XML Schemas must provide a framework for maximum extensibility, to allow vendors to compete on depth and quality of coverage.
...