defining the needs for human activity systems, publishing new perspectives on a variety of topics, consulting, training, and special projects.


Problem Statement Language/Problem Statement Analyzer (PSL/PSA) is one output from what was probably the world's largest research project in requirements modelling. Requirements Analytics™ has a project underway to make PSL/PSA available again as an open source project.

PSL/PSA has been used for both small and large (some very large) projects. It is normally used to model software requirements, but it is not restricted to that. Where a client prefers a variation from the standard PSL/PSA that can be generated, or a client can develop a required variation in a workshop that also acts as a training environment for those likely to use the language.


  1. PSL/PSA Introduction


  1. Using PSL/PSA to Establsih Requirements
  2. Understanding Completeness and Consistency Standards
  3. Creating Corporate Data Models


  1. Using the Problem Statement Language
  2. Analyzing Requirements with the Problem Statement Analyzer
  3. Implementing Completeness Standards
  4. Using PSL/PSA to Create Standards Compliant Requirements Specifications
  5. View Integration System

PSL/PSA Summary

Problem Statement Language (PSL) and Problem Statement Analyzer (PSA), usually referred to as PSL/PSA, are probably the first tools to support requirements modelling and analysis. It is likely that PSL/PSA still remains the most comprehensive set of tools able to model system and software requirements for systems of an unlimited size, and capable of checking such a set of requirements for completeness and consistency. It is based on an  object property relationship approach that has substantial academic rigour behind it since before 1928. The tools themselves have been evolving since 1968, but have not been available for some years now (see History). PSL/PSA has not yet been replaced by anything else more suitable. Although UML is probably the most widely used method these days, the new PSL/PSA Project is based in part on the premise that UML has not proved itself to have the robustness and scaleability of PSL/PSA.

Using the menu at the left, you will be able to access information about PSL/PSA as it existed atthe time it was last available to the market commercially. There is information about the original ISDOS Project that produced the first few versions, the history of its evolution, names of some of the original participants in the research project, the names of some of the people involved in its development or review, the syntax of PSL, the reports available in PSA, information about the View Integration System often used to create corporate data models, and FSGEN used to create IEEE standard compliant software requirements specifications.

Please note the following:

  1. you will need to be registered and logged in to access information below this top level article;
  2. content is being developed and added to this website during the 1st and 2nd quarters of 2011, so do not be surprised if the full PSL syntax is not available until July 2011;
  3. while the material is being transferred to this website, some of the links will take you to the original psl/psa website - you will need to use the browser back button to navigate back to here;
  4. as this section of the website develops, more discussion will be made available in the associated Wiki which will have discussions well beyond the syntax only.