A computerized system that can be used for the development and analysis of an expression of requirements and to provide assistance during system design. The expression of requirements is maintained in a database: PSL is the input language to this database while PSA is the management system and report generator for the database.

The basic database model consists of objects that may have properties and may be interconnected by means of relationships. PSA permits the analysis of the database and the production of various kinds of report, e.g. on database modifications, database content, and on unused data objects or breaks in information flow.

PSL/PSA was developed by Daniel Teichroew on the ISDOS project at the University of Michigan. The system was implemented on a wide range of computers and was used extensively by many organizations.