Logic Programming Associates

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Logic Programming Associates Ltd
IndustryComputer software
Area served
UK, United States, EMEA
Key people
directors: Clive Spenser
Brian Steel
ProductsVisiRule, Flex expert system toolkit, Flint toolkit, LPA Prolog for Windows
Websitewww.lpa.co.uk, www.visirule.co.uk

Logic Programming Associates (LPA) is a company specializing in logic programming and artificial intelligence software. LPA was founded in 1980[1] and is widely known for its range of Prolog compilers and more recently for VisiRule.

LPA was established to exploit research at the Department of Computing and Control at Imperial College London into logic programming carried out under the supervision of Prof Robert Kowalski. One of the first implementations made available by LPA was micro-PROLOG[2] which ran on popular 8-bit home computers such as the Sinclair Spectrum[3] and Apple II. This was followed by micro-PROLOG Professional one of the first Prolog implementations for MS-DOS.

As well as continue with Prolog compiler technology development, LPA has a track record of creating innovative associated tools and products to address specific challenges and opportunities.

In 1989, LPA developed the Flex expert system toolkit, which incorporated frame-based reasoning with inheritance, rule-based programming and data-driven procedures. Flex has its own English-like Knowledge Specification Language (KSL) which means that knowledge and rules are defined in an easy-to-read and understand way.

In 1992, LPA helped set up the Prolog Vendors Group,[4] a not-for-profit organization whose aim was to help promote Prolog by making people aware of its usage in industry.

In 2000, LPA helped set up Business Integrity Ltd, to bring to market document assembly technology. This lead the creation of Contract Express which became sold to most major law firms. In 2015, Thomson Reuters acquired Business Integrity Ltd.

LPA's core product is LPA Prolog for Windows,[5] a compiler and development system for the Microsoft Windows platform. The current LPA software range comprises an integrated AI toolset which covers various aspects of Artificial Intelligence including Logic Programming, Expert Systems, Knowledge-based Systems, Data Mining, Agents and Case-based reasoning etc.

In 2004, LPA launched VisiRule [6] a graphical tool for developing knowledge-based and decision support systems. VisiRule has been used in various sectors, to build legal expert systems, machine diagnostic programs, medical and financial advice systems, etc.


For many years, LPA has worked closely with Valdis Krebs, an American-Latvian researcher, author, and consultant in the field of social and organizational network analysis. Valdis is the founder and chief scientist of Orgnet, and the creator of the popular Inflow [7] software package.

External links[edit]


  1. ^ "LPA Company Background". 2005-02-05. Retrieved 2018-08-29.
  2. ^ Microcomputer PROLOG implementations (PDF), retrieved 2013-04-29
  3. ^ micro-PROLOG for Sinclair Spectrum, retrieved 2013-04-29
  4. ^ Prolog Vendors Group Launched (PDF), retrieved 2013-04-29
  5. ^ LPA Prolog for Windows, retrieved 2013-04-29
  6. ^ VisiRule, retrieved 2020-01-04
  7. ^ InFlow