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Photo of Gerry Wolff Gerry Wolff, ORCID: 0000-0002-4624-8904, short BIO and longer BIO.

Too blue for logic

My axioms were so clean-hewn,
The joins of 'thus' and 'therefore' neat
But, I admit
Life would not fit
Between straight lines
And all the cornflowers said was 'blue,'
All summer long, so blue.
So when the sea came in and with one wave
Threatened to wash my edifice away -
I let it.

Marianne Jones

SP GROUP: If you would like to receive occasional news about progress in the SP programme of research, please contact me, Gerry Wolff, via email or phone. There is information about the SP group here: SP GROUP.

NOTE: It may seem odd that, amongst the publications detailed below, there is a relatively big gap between the publication of the book Unifying Computing and Cognition in 2006 and later publications beginning with The SP Theory of Intelligence: an overview (PDF, Information, 4 (3), 283-341, 2013, in 2013. This is because, from early 2006 to late 2012, I was working full time on campaigns related to climate change. Because of the large carbon footprint from flying, I'm trying to avoid it as much as possible. Online conferences also have a carbon footprint but that is easier to fix than the carbon footprint from flying.



  • Documents, listed below, which are peer-reviewed and published, are marked 'PRP'.
  • All the peer-reviewed, published papers listed on this page are 'open access' and can be read without charge or other impediment.
  • There is a download link for every document except the book Unifying Computing and Cognition.

The SP system:

Distinctive features and advantages of the SP system

Potential benefits and applications

 Development of the SP Machine

Conference papers



The SP Theory of Intelligence is a unique attempt to integrate and simplify observations and concepts across artificial intelligence, mainstream computing, mathematics, and human perception and cognition, with information compression as a unifying theme.

The name "SP" is short for simplicity and power, because compression of any given body of information, I, may be seen as a process of reducing informational “redundancy” in I and thus increasing its “simplicity”, whilst retaining as much as possible of its non-redundant expressive “power”.

Central in the theory is the powerful concept of multiple alignment, with versatility in the representation of knowledge and in AI functions.

The SP theory is realised in the form of a computer model, SP71. This model may be seen as a first version of the SP machine, an expression of the SP theory and a means for it to be applied. Source code for the model, with associated files, may be downloaded via links under the heading 'SOURCE CODE', below.

The SP theory combines conceptual simplicity with descriptive and explanatory power in several areas, including concepts of 'computing', the representation of knowledge, natural language processing, pattern recognition, several kinds of reasoning, the storage and retrieval of information, planning and problem solving, unsupervised learning, information compression, and human perception and cognition.

An introduction to the ideas is in the slide show The SP Theory of Intelligence (PDF)—see below. A much fuller account is in the book Unifying Computing and Cognition.

The background and motivation for the research is described in Computing, cognition and information compression (PDF).


Unless it is self-explanatory, each slide has one or more notes, each one shown with a 'speech bubble' icon, normally in the top left-hand corner. To see a note, position the cursor over the icon. If the whole note is not visible, right-click on the icon and choose "Open pop-up note".

To view a presentation, it is probably best to download the file and open it in the Adobe Reader. Other systems may not show the notes properly. Controls: Full screen: CTRL-L; Escape from full screen: ESC; Zoom in: CTRL-plus; Zoom out: CTRL-minus; Next slide: left-click; Previous slide: right-click; Scrolling left or right, up or down: use the 'hand'.

An article, giving an overview of the SP system and its expected benefits and applications is here: The SP Theory of Intelligence: benefits and applications (PDF).


Most of the publications from this section may be obtained as a PDF, Postscript or MS Word file. The articles that give the best overall view of the research programme and the SP framework are marked with Marks articles and conference papers that give the best overall view of the research. For readers who are not previously acquainted with this field, these are the articles to start with. For convenience, they are listed here in a suggested order for reading:

Publications topics:



The SP Theory and its Applications

J Gerard Wolff, 2006, ISBN 0-9550726-0-3 (ebook edition), ISBN 0-9550726-1-1 (print edition) 

Ebook cover Pbook cover
Ebook cover Print edition cover

Description of the book

Ordering the book


A good step forward in the development of these ideas would be the creation of a new version of the SP machine. It would be:

  • Based on the SP71 computer model.
  • Built as a software virtual machine, using high-parallel search mechanisms, and with a good user interface. The high-parallel search mechanisms in an existing search engine would provide a good foundation for this version of the SP machine.
  • An open-source model, available, via the web, to the research community everywhere.
  • A vehicle for experimentation and research with two main aims:
    • To explore the range of applications of the SP machine.
    • To refine the SP theory itself.

SP machine


If you wish to see the exact workings of the SP71 computer model or experiment with it, the source code and a Windows executable is available in the file SP71.ZIP, and via "Ancillary files" under A slightly earlier version, SP70, referenced in published papers and in Unifying Computing and Cognition, may be downloaded via SP70.ZIP.

Before looking at the detailed workings of SP71, it is probably best to understand the thinking behind it, described in Unifying Computing and Cognition and The SP Theory of Intelligence: an overview (PDF, J G Wolff, Information, 4 (3), 283-341, 2013, Also, there is a relatively high level description of the workings of the program in Sections 3.9, 3.10, and 9.2 in Unifying Computing and Cognition.

It is probably best to start by looking at SP62, a subset of SP71 that lacks any ability for learning. The source code and a Windows executable is available in the file SP62.ZIP.

Please note: these programs are for research, they are not shrink-wrapped software packages that you might buy from a shop. That said, there are detailed comments in the source code which should help to clarify how the programs works. I have released them mainly for people who want to dig around inside them and see what is going on. We aim to develop a high-parallel version of the "SP machine" with a user-friendly interface. This should make things easier for anyone who wants to try out the system or improve it.

This software is released to the public domain without any restrictions, but please read the notice on the source files.


Most of the papers from this programme of research, both those which have not yet been published and those that have been published, are archived in To find these papers, search for author: Wolff_J_G in that archive.

The moderators of would not accept some papers, saying that they did not fit any of the arxiv categories, or that there was too much overlap with my other papers. These papers are:

These papers are now archived with (search under "Full Site" for "J Gerard Wolff") and (Search for "J Gerard Wolff").

From January 2019, and are the preferred archives because of the simplicity of archiving PDF files instead of TEX source files (with PDF figures) that have to be processed.

The SP71 computer model is archived here:

  • As "ancillary files" with "The SP Theory of Intelligence: an overview" in Some but not all of the notes associated with this project are archived here.

A much fuller record of the research, including all versions of the software, all the associated notes, and all the publications, has been sent for digital archiving, with agreement of relevant people in each organisation, to:

  • The National Museum of Computing at Bletchley Park, near Milton Keynes, UK. With the agreement of the archivist, Brian Aldous, a memory stick with a covering letter was sent to him on 24th of May 2016.
  • Bangor University Library, Bangor University, North Wales, UK:
    • Files were deposited with the librarian about 2005.



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