A machine based tool and associated logic and methodology are used in converting data from an input form to a target form using context dependent conversion rules. In particular, a frame-slot architecture is utilized where a frame represents an intersection between a contextual cue recognized by the machine tool, associated content and related constraint information to specific to that conversion environment, whereas a slot represents an included chunk of information. An exemplary conversion system (400) includes a parser (402) for use in parsing and converting an input stream (403) from a source (404) to provide an output stream (411) in a form for use by a target system (412). To accomplish the desired conversion, the parser (402) uses information from a public schema (406), a private schema (408) and a grammar (410). The public schema (406), private schema (408) and grammar (410) may include conversion rules applicable to less than the whole of a subject matter area including the input stream (403).