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About LPA & VisiRule

LPA: Over 42 years of Applied AI

VisiRule is 100% owned and developed by Logic Programming Associates Ltd.


LPA is a small, private UK company specialising in practical Artificial Intelligence solutions. LPA was founded back in 1981, and LPA staff, many of whom joined in the 80s, have extensive experience in designing and implementing AI solutions. LPA engineers have advised and consulted on numerous projects. 


LPA was recognized as Artificial Intelligence Innovators by CV Magazine.


In 2019, LPA joined the Barclays Eagle Labs LawTech incubator in Notting Hill, London. Go and read the full press release. There are various other smart lawtech start ups at the Lab, i.e. apart from LPA/VisiRule. You can go and inspect the latest directory of Barclays Eagle Labs LawTech current members to see what exciting ideas are being developed within the UK.


In 2020, LPA launched its VisiRule Analytics, and presented its new ChatBot module which incorporates VisiRule decision tree logic with FAQ KB access.

LexisNexis announce new digital assistant tax advisor tool developed using VisiRule

Interview with Clive Spenser

LPA Delivers A Range Of Software Development Tools For Both Programmers And Non-Programmers

microProlog Spectrum packaging
micro-Prolog for the BBC

History of LPA

LPA is the leading supplier of commercial Prolog compilers for PCs and offers a wide range of integrated AI products based. Prolog was one of the first computer programming languages to be associated with AI; the other being LISP. Prolog is still being discovered even now by a new generation of programmers.

In 1981, LPA was formed to exploit the results emerging from the logic programming research team of Prof. Bob Kowalski at Imperial College, London. Some of those making the transition from academia to industry were Brian D Steel and Clive Spenser both still with LPA. They were later joined by Alan Westwood.


LPA's initial product, micro-PROLOG, was the world's first Prolog system for small machines and was implemented on many micro-computers of the time. micro-PROLOG was years ahead of its time but severely restricted by the memory limitations of 8-bit chips i.e. 64K RAM. LPA has since built products on 16-bit, 24-bit and 32-bit PCs and now on modern 64-bit cloud based servers.

In 1995, LPA helped organize the Practical Application of Prolog event which featured presenters from Microsoft, IBM, etc. Peter Reintjes gave an inspiring tutorial on Prolog for Software Engineering.

Since then, LPA has continued to develop and sell advanced software tools, and is firmly established as a leading supplier of commercial software products and solutions in the areas of Expert Systems and Artificial Intelligence. LPA has acquired a wealth of expertise in developing and delivering disruptive applications.

LPA's current range of AI tools support companies who want to build, test and deliver intelligent applications and embedded components.

Business Integrity & Contract Express

Between 1996 and 1998, based on work co-funded through a DTI Smart award, LPA developed ScaffoldIT, a tool for building dynamic documents and intelligent web sites. This technology, built using the LPA Prolog engine and associated ProWeb Server, was able to generate complex, personalised documents such as insurance policy schedules, legal contracts, and complex sales proposals, on the Web.

To exploit this research, LPA partnered with a small London law-firm, Tarlo Lyons. Together, they set up a new company, named Business Integrity Ltd, BIL, with Clive Spenser as a Founding Director. In 2001, Legal Technology Insider reported the initial BigLaw sales of DealBuilder (as the original product was known). Linklaters signed in 2002 to convert master documents into web questions for Blue Flag.


The LPA software stack provided a solid and robust basis for Contract Express, which became adopted by many leading law firms as well as corporates such as Cisco and Microsoft. By 2012, Contract Express was being used for internal use, client facing projects and external Marketing Showcases - such as CooleyGo and Wilson Soncini's Term Sheet Generator. Jeff Thomas et al identified 14 firms offering start-up documentation using document automation tools.

As a result of the commercial success of Contract Express, BIL was acquired by Thomson Reuters in 2015. Partners and GCs trust Contract Express because lawyers are able to quickly and accurately automate and update their legal templates in Word without requiring IT specialists to convert them into programs.


This philosophy of self-service resonates with VisiRule. Self-service products allow non-programmers to create solutions via web-based question and answer sessions. Much of the underlying LPA software stack, that was initially used to create DealBuilder, and then Contract Express, now forms the basis of VisiRule.

DealMaker History of LPA and Business Integrity
Linklaters buy DealBuilder licence announcement

“VisiRule is the easiest-to-use and most versatile software that I know for building rule-based expert / recommender systems. The visual approach that VisiRule follows for representing information makes it super easy to model any rule base easily. One of the most amazing features is that VisiRule can generate working executable expert system, derived directly from the visual flowchart.” 

G.E., Associate Professor of Business Analytics

TarloLyons announce SCAFFOLD - forerunner to Contract Express

History of VisiRule

In 2004, LPA launched VisiRule, a graphical software tool which lets business users draw and deliver decision support systems, rather than have to engage programmers to write code for them. VisiRule has been extended and enhanced since then and used in many different projects ranging from machine diagnostics and fault finding to knowledge management and the automated generation of personalised financial advice and legal guidance.

AI Newletter wrote about VisiRule in August 2004.

VisiRule allows non-technical business users such as lawyers, accountants, tax advisers, healthcare professionals and field service agents, to develop and deliver decision support applications.

VisiRule was initially launched as a Windows desktop application but the run-time delivery was moved to the Web to support cloud-based deployment. Mobile phone delivery then followed as the popularity of smartphones grew. Browser-based authoring via VisiRule365 was added in 2018 along with VisiRule FastChart integration with Machine Learning.

VisiRule launch article in SD Times 2004

History of Flex

LPA developed Flex in the 1980s. Flex was quickly establshed as the leading Prolog-based expert system toolkit supporting frames, rules and procedures. Flex was licenced to other Prolog providors on other hardware platforms such as Telecomputing Plc to supplement Top One on IBM and ICL mainframes. Other implementations included Quintec Flex, Quintus Flex and BIM flex which were all running on Unix and/or Vax/VMS platforms.
Flex was adopted by the Open University as part of its course T396 which was designed by Prof Adrian Hopgood. Some of the teaching material is now available.
Flex was also use by David A Ferrucci and Selmer Bringsjord in their storytelling machine, BRUTUS.
LPA made Flex available on Windows, DOS and Macintosh PCs, and in the early 2000's developed VisiRule as a way to create Flex/KSL programs simly by drawing a diagram - no need to write any code!

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