The language is expressed using OBJECTS and RELATIONS.

There are several key steps in the PSL Language Process.

• An editor is used to create a language source file
• The source file is processed, checking for syntax errors. The langauge PSL defined as a set of objects and relations defines the consistency that must be achieved when writing PSL to produce correct input.
• When the source is "correct", it is processed to populate a PSA database.
• PSA reports are used to identify unacceptable levels of incompleteness, and a cycle of editing PSL, processing the source, and populating the PSA database is performed.

Implementing a particular method or standard for specifying systems is achieved by mapping the required combination of PSL objects and relations for each required element of the method or standard. This means that PSL/PSA can also be used to check the meta models of other CASE tools used for specification, analysis, and design.

The language evolved from 1968-1991. Key version ranges were: