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Survey of Theme One Program • 7

This is a Survey of resources relating to the Theme One Program I worked on all through the 1980s.  The aim was to develop fundamental algorithms and data structures for integrating empirical learning with logical reasoning.  I had earlier developed separate programs for basic components of those tasks, in particular, two‑level formal language learning and propositional constraint satisfaction, the latter using an extension of C.S. Peirce’s logical graphs as a syntax for propositional logic.  Thus arose the question of how well it might be possible to get “empiricist” and “rationalist” modes of operation to cooperate.  The long‑term vision is the implementation of an Automated Research Tool able to double as a platform for Inquiry Driven Education.

Wiki Hub

Documentation

Blog Series

Blog Dialogs

Applications

References

  • Awbrey, S.M., and Awbrey, J.L. (May 1991), “An Architecture for Inquiry • Building Computer Platforms for Discovery”, Proceedings of the Eighth International Conference on Technology and Education, Toronto, Canada, pp. 874–875.  Online.
  • Awbrey, J.L., and Awbrey, S.M. (January 1991), “Exploring Research Data Interactively • Developing a Computer Architecture for Inquiry”, Poster presented at the Annual Sigma Xi Research Forum, University of Texas Medical Branch, Galveston, TX.
  • Awbrey, J.L., and Awbrey, S.M. (August 1990), “Exploring Research Data Interactively • Theme One : A Program of Inquiry”, Proceedings of the Sixth Annual Conference on Applications of Artificial Intelligence and CD-ROM in Education and Training, Society for Applied Learning Technology, Washington, DC, pp. 9–15.  Online.

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Survey of Differential Logic • 8

This is a Survey of work in progress on Differential Logic, resources under development toward a more systematic treatment.

Differential logic is the component of logic whose object is the description of variation — the aspects of change, difference, distribution, and diversity — in universes of discourse subject to logical description.  A definition as broad as that naturally incorporates any study of variation by way of mathematical models, but differential logic is especially charged with the qualitative aspects of variation pervading or preceding quantitative models.  To the extent a logical inquiry makes use of a formal system, its differential component treats the use of a differential logical calculus — a formal system with the expressive capacity to describe change and diversity in logical universes of discourse.

Elements

Blog Series

Architectonics

Applications

Blog Dialogs

Explorations

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Survey of Animated Logical Graphs • 8

This is a Survey of blog and wiki posts on Logical Graphs, encompassing several families of graph‑theoretic structures originally developed by Charles S. Peirce as graphical formal languages or visual styles of syntax amenable to interpretation for logical applications.

Beginnings

Elements

Examples

Blog Series

  • Logical Graphs • Interpretive Duality • (1)(2)(3)(4)
  • Logical Graphs, Iconicity, Interpretation • (1)(2)
  • Genus, Species, Pie Charts, Radio Buttons • (1)

Excursions

Applications

Anamnesis

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Cactus Language • Preliminaries 9

We now have the materials in place to formulate a definition of our subject.

The painted cactus language with paints in the set is the formal language defined as follows.

In the idiom of formal language theory, a string is called a sentence of if and only if it belongs to or simply a sentence if the language is understood.  A sentence of is referred to as a painted and rooted cactus expression on the palette or a cactus expression for short.

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Cactus Language • Preliminaries 8

Defining the basic operations of concatenation and surcatenation on arbitrary strings gives them operational meaning for the all‑inclusive language   With that in hand it is time to adjoin the notion of a more discriminating grammaticality, in other words, a more properly restrictive concept of a sentence.

If is an arbitrary formal language over an alphabet of the type we have been discussing, that is, an alphabet of the form then there are a number of basic structural relations which can be defined on the strings of

Concatenation

is the concatenation of and in
if and only if
is a sentence of is a sentence of
and

is the concatenation of the strings in
if and only if
is a sentence of for all
and

Discatenation

is the discatenation of by
if and only if
is a sentence of is an element of
and

in which case we more commonly write

Subclause

is a subclause of
if and only if
is a sentence of
and
ends with a

Subcatenation

is the subcatenation of by
if and only if
is a subclause of is a sentence of
and

Surcatenation

is the surcatenation of the strings in
if and only if
is a sentence of for all
and

The converses of the above decomposition relations amount to the corresponding composition operations.  As complementary forms of analysis and synthesis they make it possible to articulate the structures of strings and sentences in two directions.

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Cactus Language • Preliminaries 7

The array of syntactic operators may be put in more organized form by making a few additional conventions and auxiliary definitions.

Concatenation

The conception of concatenation permits extension to its natural prequel, the corresponding operator on zero operands.

From that beginning the operation of concatenation may be broken into stages by means of the following conceptions.

The precatenation of two strings is defined as follows.

The concatenation of strings may now be given a new definition as the iterated precatenation of strings beginning with and continuing through the remaining strings.

Surcatenation

The conception of surcatenation permits extension to its natural prequel, the corresponding operator on zero operands.

From that beginning the operation of surcatenation may be broken into stages by means of the following conceptions.

A subclause in is a string ending with

The subcatenation of a subclause by a string is defined as follows.

The surcatenation of strings may now be given a new definition as the iterated subcatenation of strings beginning with and continuing through the remaining strings.

Notice that the expressions and are defined in such a way that the respective operators and simply ignore, in the manner of constants, whatever sequences of strings may be listed as their ostensible arguments.

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Cactus Language • Preliminaries 6

The definitions of the syntactic connectives can be made a little more succinct by defining the following pair of generic operators on strings.

Concatenation

The concatenation of the sequence of strings is defined recursively as follows.

Surcatenation

The surcatenation of the sequence of strings is defined recursively as follows.

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Cactus Language • Preliminaries 5

The easiest way to define the language is to indicate the general run of operations required to construct the greater share of its sentences from the designated few which require a special election.

To do that we introduce a family of operations called syntactic connectives on the strings of   If the strings on which they operate are already sentences of then the operations amount to sentential connectives.  If the syntactic sentences, viewed as abstract strings of uninterpreted signs, are provided with a semantics where they denote propositions, in other words, indicator functions on a universe of discourse, then the operations amount to propositional connectives.

Rather than presenting the most concise description of cactus languages right from the beginning, it aids comprehension to develop a picture of their forms in gradual stages, starting with the most natural ways of viewing their elements, if somewhat at a distance, and working through the most easily grasped impressions of their structures, if not always the sharpest acquaintances with their details.

We begin by defining two sets of basic operations on strings of

Concatenation

The concatenation of one string is the string

The concatenation of two strings is the string

The concatenation of strings is the string

Surcatenation

The surcatenation of one string is the string

The surcatenation of two strings is the string

The surcatenation of strings is the string

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Cactus Language • Preliminaries 4

The informal mechanisms illustrated in the preceding discussion equip us with a description of cactus language adequate to providing conceptual and computational representations for the minimal formal logical system variously known as propositional logic or sentential calculus.

The painted cactus language is actually a parameterized family of languages, consisting of one language for each set of paints.

The alphabet is the disjoint union of the following two sets of symbols.

is the alphabet of markers, the set of punctuation marks, or the collection of syntactic constants common to all the languages   Various ways of representing the elements of are shown in the following display.

is the palette, the alphabet of paints, or the collection of syntactic variables peculiar to the language   The set of signs in may be enumerated as follows.

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Cactus Language • Preliminaries 3

A few definitions from formal language theory are required at this point.

An alphabet is a finite set of signs, typically,

A string over an alphabet is a finite sequence of signs from

The length of a string is just its length as a sequence of signs.

The empty string is the unique sequence of length 0.  It is sometimes denoted by an empty pair of quotation marks, “”, but more often by the Greek symbols epsilon or lambda.

A sequence of length is typically presented in the following concatenated forms.

or

with for all

The following notations provide useful alternatives.

 =  “”  =  the empty string.

 =   =  the language consisting of a single empty string.

Several operations on strings find sufficient application to motivate the following definitions.

To erase an appearance of a sign is to replace it with an appearance of the blank symbol “ ”.

To delete an appearance of a sign is to replace it with an appearance of the empty string “”.

If is a string which ends with a sign then is the string which results by deleting the terminal from

A token is a particular appearance of a sign.

Finally —

The kleene star of alphabet is the set of all strings over   In particular, includes among its elements the empty string

The kleene plus of an alphabet is the set of all positive length strings over in other words, everything in but the empty string.

A formal language over an alphabet is a subset of   In brief,   If is a string over and is an element of then it is customary to call a sentence of   Thus, a formal language is defined by specifying its elements, which amounts to saying what it means to be a sentence of

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Cactus Language • Preliminaries 2

As a temporary notation, let the relationship between a particular sign and a particular object , namely, the fact that denotes or the fact that is denoted by , be symbolized in one of the following two ways.

Now consider the following paradigm.

In the same vein, if we let the sign “blank” denote the sign “ ” then the string of characters inside the first pair of quotation marks will serve as another name for the string of characters inside the second pair of quotation marks.  In other words, “blank” is a higher order sign whose object is the sign “ ” and the string of five characters inside the first pair of quotation marks is a sign at a higher level of signification than the string of one character inside the second pair of quotation marks.  The relation in question can be abbreviated in either one of the following two ways.

Using the raised dot “∙” as a sign to mark the articulation of a quoted string into a sequence of possibly shorter quoted strings, and thus to mark the concatenation of a sequence of quoted strings into a possibly larger quoted string, one can write the following equation.

The above tactic lets us refer to the blank as a type of character and refer to any blank we choose as a token of that type, denoting either in a markèd way, but without the use of quotation marks.  As a blank is just what the name “blank” names, it is possible to represent the denoting of the sign “ ” by the name “blank” in the form of an identity between the named objects, as follows.

Given the above identities it is possible to extend the use of the “∙” sign to mark the articulation of either named or quoted strings into both named and quoted strings.  For example, we have the following equations.

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Cactus Language • Preliminaries 1

Thus, what looks to us like a sphere of scientific knowledge more accurately should be represented as the inside of a highly irregular and spiky object, like a pincushion or porcupine, with very sharp extensions in certain directions, and virtually no knowledge in immediately adjacent areas.  If our intellectual gaze could shift slightly, it would alter each quill’s direction, and suddenly our entire reality would change.

Picture two different configurations of such an irregular shape, superimposed on each other in space, like a double exposure photograph.  Of the two images, the only part which coincides is the body.  The two different sets of quills stick out into very different regions of space.  The objective reality we see from within the first position, seemingly so full and spherical, actually agrees with the shifted reality only in the body of common knowledge.  In every direction in which we look at all deeply, the realm of discovered scientific truth could be quite different.  Yet in each of those two different situations, we would have thought the world complete, firmly known, and rather round in its penetration of the space of possible knowledge.

Herbert J. Bernstein • “Idols of Modern Science”

The task before us is to describe the syntax of a family of formal languages intended for use as a sentential calculus, and thus interpreted for the purpose of reasoning about propositions and their logical relations.

To carry out our discussion we need a way of referring to signs as if they were objects like any others, in other words, as the sorts of things which can be named, indicated, described, discussed, and renamed if necessary, which can be placed, arranged, and rearranged within a suitable medium of expression — or else manipulated in the mind — which can be articulated and decomposed into their elementary signs, and which can be strung together in sequences to form complex signs.

Signs having signs as their objects are known as “higher order signs”, a topic which demands an adequate level of formalization, but in due time.  The present discussion needs a quicker way to get into the subject, even if it settles for informal means which cannot be rendered absolutely precise.

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Cactus Language • Overview 4

Depending on whether a formal language is called by the type of sign it enlists or the type of object its signs denote, a cactus language may be called a sentential calculus or a propositional calculus, respectively.

When the syntactic definition of a language is well enough understood the language can begin to acquire a semantic function.  In natural circumstances the syntax and the semantics are likely to be engaged in a process of co‑evolution, whether in ontogeny or in phylogeny, which is to say the two developments tend to form parallel sides of a single bootstrap.  But that is not always the easiest way, at least not at first, to formally comprehend the nature of their action or the power of their interaction.

According to the customary modes of formal reconstruction, a language of the type we are considering is first presented in terms of its syntax, in other words, as a formal language of strings called sentences, and thus amounting to a particular subset of the possible strings which can be formed on a finite alphabet of signs.  A syntactic definition of a specific cactus language which proceeds along purely formal lines is carried out in Cactus Language • Syntax.  After that, the development of the language’s more concrete aspects can be seen as a matter of defining the following two functions.

  • The first is a function which takes each sentence of the language into a computational data structure, namely, a generalized tree‑like parse graph called a painted cactus.
  • The second is a function which takes each sentence of the language or its interpolated parse graph into a logical proposition, ending with an indicator function as the object denoted by the sentence.

The discussion of syntax brings up a number of associated issues which need to be clarified before going on.  They may be thought of as questions of style, in other words, the manner of description, grammar, or theory one finds available or chooses as preferable for a given language.  Those issues are discussed in Cactus Language • Stylistics.

There is an aspect of syntax so schematic in its basic character that it can be conveyed by computational data structures, so algorithmic in its uses that it can be automated by routine mechanisms, and so fixed in its nature that its practical exploitation can be served by the usual devices of computation.  Because it involves the transformation of signs it can be recognized as an aspect of semiotics.  Since it can be carried out in abstraction from meaning it is not up to the level of semantics, much less a complete pragmatics, though it does incline to the pragmatic aspects of computation which are auxiliary to and incidental to the human use of language.  That aspect of formal language use may be described as the algorithmics or mechanics of language processing.  A mechanical conversion of cactus languages into their associated data structures is discussed in Cactus Language • Mechanics.

In the usual way of proceeding on formal grounds, meaning is added by giving each grammatical sentence, or each syntactically distinguished string, an interpretation as a logically meaningful sentence, in effect, equipping or providing each abstractly well‑formed sentence with a logical proposition for it to denote.  A semantic interpretation of cactus language is carried out in Cactus Language • Semantics.

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Cactus Language • Overview 3

In the development of Cactus Language to date the following two species of graphs have been instrumental.

  • Painted And Rooted Cacti (PARCAI).
  • Painted And Rooted Conifers (PARCOI).

It suffices to begin with the first class of data structures, developing their properties and uses in full, leaving discussion of the latter class to a part of the project where their distinctive features are key to developments at that stage.  Partly because the two species are so closely related and partly for the sake of brevity, we’ll always use the genus name “PARC” to denote the corresponding cacti.

To provide a computational middle ground between sentences seen as syntactic strings and propositions seen as indicator functions the language designer must not only supply a medium for the expression of propositions but also link the assertion of sentences to a means for inverting the indicator functions, that is, for computing the fibers or inverse images of the propositions.

Given a body of conceivable propositions we need a way to follow the threads of their indications from their object domain to their values for the mind and a way to follow those same threads back again.  Moreover, we need to implement both ways of proceeding in computational form.  Thus we need programs for tracing the clues sentences provide from the universe of their objects to the signs of their values and, in turn, from signs to objects.  Ultimately, we need to render propositions so functional as indicators of sets and so essential for examining the equality of sets as to give a rule for the practical conceivability of sets.  Tackling that task requires us to introduce a number of new definitions and a collection of additional notational devices, to which we now turn.

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Differential Propositional Calculus • 37

Foreshadowing Transformations • Extensions and Projections of Discourse

And, despite the care which she took to look behind her at every moment, she failed to see a shadow which followed her like her own shadow, which stopped when she stopped, which started again when she did, and which made no more noise than a well‑conducted shadow should.

— Gaston Leroux • The Phantom of the Opera

Many times in our discussion we have occasion to place one universe of discourse in the context of a larger universe of discourse.  An embedding of the type is implied any time we make use of one basis which happens to be included in another basis   When discussing differential relations we usually have in mind the extended alphabet has a special construction or a specific lexical relation with respect to the initial alphabet one which is marked by characteristic types of accents, indices, or inflected forms.

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Differential Propositional Calculus • 36

Transformations of Discourse

It is understandable that an engineer should be completely absorbed in his speciality, instead of pouring himself out into the freedom and vastness of the world of thought, even though his machines are being sent off to the ends of the earth;  for he no more needs to be capable of applying to his own personal soul what is daring and new in the soul of his subject than a machine is in fact capable of applying to itself the differential calculus on which it is based.  The same thing cannot, however, be said about mathematics;  for here we have the new method of thought, pure intellect, the very well‑spring of the times, the fons et origo of an unfathomable transformation.

— Robert Musil • The Man Without Qualities

Here we take up the general study of logical transformations, or maps relating one universe of discourse to another.  In many ways, and especially as applied to the subject of intelligent dynamic systems, the argument will develop the antithesis of the statement just quoted.  Along the way, if incidental to my ends, I hope the present essay can pose a fittingly irenic epitaph to the frankly ironic epigraph inscribed at its head.

The goal is to answer a single question:  What is a propositional tangent functor?  In other words, the aim is to develop a clear conception of what manner of thing would pass in the logical realm for a genuine analogue of the tangent functor, an object conceived to generalize as far as possible in the abstract terms of category theory the ordinary notions of functional differentiation and the all too familiar operations of taking derivatives.

As a first step we examine the types of transformations we already know as extensions and projections and we use their special cases to illustrate several styles of logical and visual representation which figure in the sequel.

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Differential Propositional Calculus • 35

Example 2. Drives and Their Vicissitudes (concl.)

Applied to the example of ‑gear curves, the indexing scheme results in the data of the next two Tables, showing one period for each orbit.

The states in each orbit are listed as ordered pairs where may be read as a temporal parameter indicating the present time of the state and where is the decimal equivalent of the binary numeral

Grasped more intuitively, the Tables show each state with a subscript equal to the numerator of its rational index, taking for granted the constant denominator   In that way the temporal succession of states can be reckoned by a parallel round‑up rule.  Namely, if is any pair of adjacent digits in the state index then the value of in the next state is

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Differential Propositional Calculus • 34

Example 2. Drives and Their Vicissitudes (cont.)

With a little thought it is possible to devise a canonical indexing scheme for the states in differential logical systems.  A scheme of that order allows for comparing changes of state in universes of discourse that weigh in on different scales of observation.

To that purpose, let us index the states with the dyadic rationals (or the binary fractions) in the half-open interval   Formally and canonically, a state is indexed by a fraction whose denominator is the power of two and whose numerator is a binary numeral formed from the coefficients of state in a manner to be described next.

The differential coefficients of the state are the values for where is defined as identical to   To form the binary index of the state the coefficient is read off as the binary digit associated with the place value   Expressed in algebraic terms, the rational index of the state is given by the following equivalent formulations.

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Differential Propositional Calculus • 33

Example 2. Drives and Their Vicissitudes (cont.)

Expressed in the language of drives and gears our next Example may be described as the family of fourth‑gear curves through the fourth extension   Those are the trajectories generated subject to the dynamic law where it’s understood all higher order differences are equal to

Because and all higher differences are fixed, the state vectors vary only with respect to their projections as points of   Thus there is just enough space in a planar venn diagram to plot the orbits and show how they partition the points of   It turns out there are just two possible orbits, of eight points each, as shown in the following Figure.


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Differential Propositional Calculus • 32


I open my scuttle at night and see the far‑sprinkled systems,
And all I see, multiplied as high as I can cipher, edge but
     the rim of the farther systems.

— Walt Whitman • Leaves of Grass

Example 2. Drives and Their Vicissitudes

Before we leave the one‑feature case let’s look at a more substantial example, one which illustrates a general class of curves through the extended feature spaces and affords an opportunity to discuss important themes concerning their structure and dynamics.

As before let   The discussion to follow considers a class of trajectories having the property that for all greater than a fixed value and indulges in the use of a picturesque vocabulary to describe salient classes of those curves.

Given the above finite order condition, there is a highest order non‑zero difference exhibited at each point of any trajectory one may consider.  With respect to any point of the corresponding curve let us call that highest order differential feature the drive at that point.  Curves of constant drive are then referred to as ‑gear curves.

  • Note.  The fact that a difference calculus can be developed for boolean functions is well known and was probably familiar to Boole, who was an expert in difference equations before he turned to logic.  And of course there is the strange but true story of how the Turin machines of the 1840s prefigured the Turing machines of the 1940s.  At the very outset of general purpose mechanized computing we find the motive power driving the Analytical Engine of Babbage, the kernel of an idea behind all of his wheels, was exactly his notion that difference operations, suitably trained, can serve as universal joints for any conceivable computation.

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