combinations as unreasonable for example the bare lexicon database may include the word 34 diaper bag 34 as an item type but only after processing the pre existing data can the system determine that 34 diaper bag 34 item may be modified by certain material types like 34 denim 34 if the pre existing data were parsed with all of the constraints enabled the acceptable material types could not be identified because the relationships between item types and material types are not yet known when the pre existing data is parsed this problem is avoided by allowing certain constraints of grammar database to be disabled when parsing exemplary clauses disabling certain lexical feature tests during parsing permits the system to capture information on permissible word sequences therefore feature parser 130 preferably determines whether a given constraint from grammar database 110 can be disabled during the parsing of exemplary clauses parser 130 can make this determination by testing an indicator or signal that indicates whether the constraint can be disabled in the above example the constraint requiring a material that precedes an item share a common fabric feature would be switchable the 34 u02dc u03b5 34 indicator would mean the constraint could be disabled thus when feature parser 130 parses input exemplary clauses sequences like 34 denim diaper bag 34 34 denim jeans 34 34 cashmere diaper.