Tracing occurrences of patterns in symbolic computations

A report is made on the present state of development of a project to construct a tracing aid for users of symbolic computing systems that are written in LISP (or, in principle, any similar high-level language). The traces in question are intended to provide information which is primarily in terms that are natural for a user, e.g. on patterns of actions performed on his data, or patterns occurring in the data themselves during the operation of his program. Patterns are described in a syntax which is inspired by SNOBOL.