1. A method for determining whether a document is acceptable or rejected for use by an apparatus, said apparatus comprising a parser for parsing said document, wherein the document is stored on a computer-readable storage medium and includes 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; compiling 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 execute steps of: (a) determining a similarity score for 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) mapping 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.