15. A method of determining whether one or more documents are acceptable or rejected for use by an apparatus, said apparatus comprising a parser for parsing said document, wherein the documents are stored on a computer-readable storage medium and each include plural elements and attributes arranged according to a schema of elements and attributes, said method comprising the steps of: using a computer to determine a version of the document; using a computer to compile a metaschema based on the parser and the determined version of the document, said metaschema providing a set of rules for a valid change of the schema, each of the set of rules comprising a value and an expression of at least one of an element and an attribute of the schema; using a computer to: (a) determine a similarity score for each said document by comparing at least one of the elements and the attributes of said document to the value and the expression of at least one of an element and an attribute of the schema in the metaschema; and (b) map the document to the schema to produce a list of data values for information requested from the compiled metaschema; and using a computer to use the similarity score to accept or reject further use of the document, wherein the list of data values is used to extract information from the mapped document if the document is accepted for further use.
15. A method of determining whether one or more documents are acceptable or rejected for use by an apparatus, said apparatus comprising a parser for parsing said document, wherein the documents are stored on a computer-readable storage medium and each include plural elements and attributes arranged according to a schema of elements and attributes, said method comprising the steps of: using a computer to determine a version of the document; using a computer to compile a metaschema based on the parser and the determined version of the document, said metaschema providing a set of rules for a valid change of the schema, each of the set of rules comprising a value and an expression of at least one of an element and an attribute of the schema; using a computer to: (a) determine a similarity score for each said document by comparing at least one of the elements and the attributes of said document to the value and the expression of at least one of an element and an attribute of the schema in the metaschema; and (b) map the document to the schema to produce a list of data values for information requested from the compiled metaschema; and using a computer to use the similarity score to accept or reject further use of the document, wherein the list of data values is used to extract information from the mapped document if the document is accepted for further use. 16. The method according to claim 15 , comprising the further step of: ranking the documents according to the determined similarity scores.