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The Designing of a Logic Reasoning Methodology

, 29 Mar 2013 CPOL 5.8K 15
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Article about designing of a logic reasoning system


The interest of building a PC parser (predicate calculus) has been always puzzling me. Ever since the time I was first introduced to the  simplicity of deductive reasoning in the early 90s, I have always wanted to create a parser for the rules which to be named as my PC parser. Here I  describe why, an how of this step as we see English sentences, logics, and computer reasoning as one in our attempt to build such a mechanism.

To understand the relationship of logic reasoning and English language, we need to see the grammatical rules of English language; and how a predicate  calculus can be constructed on it. Logical reasoning, especially deductive logic in the computational form of the predicate calculus (propositional  calculus) is established as such that: all the predicates (sentences) form the basis of the reasoning and the foundation of the knowledge closure; and we test  our conclusion (a test sentence) through the traversal of these predicate sentences which have been parsed using set of PC rules.

A simple English sentence may be: Tom loves Lucy where Tom is the subject, “love” is the action, and Lucy is the object. And in C#, we parse each  English sentence using pattern matching in regular expressions.

An Abstract Attempt 

Below I have randomly written some outrageous pattern matching schemes that in a way to promote a simple way to confine our search to a set of very simple grammatical sentences.

A simple sentence pattern may be:

((a|the) )?(\w)+ (am|is|was|were|are|had been|have been) ((a|the) )?(\w)+


                A dog is a friend

                Dogs are friends

                Doug is a friend

                Doug is furious

An prepositional sentence pattern has relationship of subject and object with object prepositions such as “after, around, from, ….”

((a|the) )?(\w)+ (am|is|was|were|are|had been|have been) (\w)+ (after|in|from|around|at|about) ((a|the) )?(\w)+

Where word after “be” is an adverb, a verb in continuous form, or in the past tense describing the action is done as with the “be” to form an adverb describing the subject.


                Doug is furious about the situation

Therefore we can define a conjugational sentence with preposition can be:

                Tom is furious about love, money, and power.

                Tom is both a romantic lover and a greedy merchant

                Chris was angry and Lucy lost her patience

                He can only choose either to hate or to ignore it.

And its pattern

                ((a|the|an) )?(\w+) (is|was|am|are|were|had been|have been|has been) (\w+) (after|in|from|around|at|about) (a |the )?(\w+, )+(\w+)(,)? (and|or) (\w+)


For a sentence should have either an implicit timeline or a detailed explicit timeline.

So we can say:

Tom has been very anxious in the past. (S1)

Or we can say:

                Tom has been very anxious in the past two weeks.

An implicit timeline covers the following timely terms in some vague sense:

Long ago, past, recently, now, later, tomorrow, in a few days, in the future.

So (S1) includes time period from Long ago -> now. Given no other predicate conditions,  we can then draw conclusion:

                Tom still feels anxious right now.

Design Requirement of a Logical Sentence Parser

The design requirement of a reasonable logical sentence parser should at least draw a subset of the grammatical logical structure of a discipline of the English grammar. In a discipline we mean that we don’t want to say whatever, but follow a set of rules of expression in the writing of our reasoning. So to form a list of logical predicate sentences as a closure to our conclusion, we call this clearly as the propositions. And the propositions must be true and can directly lead to our presumption or we say our test string in order for the predicate test to be true. So our job is to conclusively test the supplied test sentence whether it should return a Boolean value of True or False, or otherwise uncertain (value of Null) from the test as the propositions are not enough for the conclusion to be drawn.

So we start by list out our propositions in a list we call the PropositionList -> typed List<string>.  This list is a class that uses a List<string> to store sentences. First of all, we gather all of the sentence to form our little universe in the list. Then we parse all the sentences, first is to ensure they are in grammatical forms that fit to our set of rules by pattern matching of the sentences using regular expressions. This also defines the sentence types may it in the PC (Predicate Calculus) been defined as simple (subject verb object), compound (conjugations) or conditional (if and iff) for example.

For simplicity we like to begin with a most reasonably simple discipline (grammatical rules) of our logical construct. By examples, so we like to same in the most simple and elegant manner of the following :

  1. Tom is late           (simple adverb predicate)
  2. Tom shoots a gun (simple action predicate)
  3. Chris loves Lucy but Lucy hates Chris (this is a simple conjunction of AND operator)
  4. Chris loves gun and rose (this can be separated into two simple predicate)
  5. Chris knows neither Tom nor Nancy (another simple conjugation)

These simple rules would allow us to interact with a small set of grammatical sentences to which we accept as our language. And we need to keep a dictionary of action words (or verbs) in all the tenses. In the real world PC implementation we should have the complete dictionary as reference.

So we like to define the following (most simple):

                Sentence = SimpleSentence | CompoundSentence | ConditionalSentence

                SimpleSentence = Subject Action Object

                CompoundSentence = SimpleSentence and|or SimpleSentence

                ConditionalSentence = IF SimpleSentence THEN SimpleSentence

Then we parse our sentences in a loop which also produce a term(symbol) table lookup. And we have a predicate list which sort of like the following:

                T loves L

                L loves T | L loves C

                If not (A loves B) then A hates B

                L hates C

And in the symbol lookup we have accumulate the following T = Tom, L = Lucy, and C = Chris. And we supply our test sentence: L loves T? And our nice predicate parser will parse all of them, so the conclusion is true. On the other hand, if we test: L Hates T; we will have a unresolved condition at 2nd sentence, so the conclusion would be false.

Another Look: Graphical Interpretations

Another approach to implement this simple logical grammar parser (or of PC – predicate logic reasoning), we will take a look at the graphical presentation and interpretation of nodes by traversal to derive or similarly to parse the conclusion.

Using Subject and Object as nodes: these include both nouns and adverbs of describing conditions; and also using BE (is, am, are, etc.) and action verbs are pointers we can describe our closed universe as a labeled graph.

The flowing is our little list of propositions (predicates):

  1. Tom loves Lucy
  2. Chris loves Lucy but Lucy hates Chris
  3. Lucy loves either Tom or Chris (Lucy must love one, we know it for sure!)

So we want to parse our conclusion that Lucy loves Tom. And first we need to quickly construct our little graphical presentation by parsing the nodes… And the result is as follows:

Our dictionary of terms:

Key        Value

Tom       T

Lucy       L

Chris      C

We need to draw a minimum set of disjoint graphs.

So in the graph, the strait blue pointers represent direct connection of two nodes with action label. And the curved separator represents a OR condition with labeled action. Up to here we do need some more details in our dictionary – we probably need a thesaurus to tell us what words are similar or opposite, so we can tell that “love” and “hate” are opposite each other. And our conclusive test sentence: Does Lucy Love Tom? We draw the test pointer in yellow…

So we go from node ‘L’, and we see that ‘L’ can either ‘Love’ Tom or ‘Love’ Chris; and ‘L’ Hate Chris. But can the yellow pointer be legal? From here we test all joint edges (or arcs) to see if they are legal. This should be a O(n) algorithm since we test each edge only once.  But if we are to test Lucy Hates Tom – presented in the red curved arrow, we shouldn’t be parsing all edges legally. Because from here we will have these a contradiction: L (hate)-> T(e1); T (love)-> L(e2); L either(love)->T or(love)->C(e3); (but e1 invalidates L(hate)->C(e4). So this parse draws false conclusion for the test sentence. And we also know by thesaurus and negation (PC) that Lucy Hates Tom is false means Lucy Loves Tom is true. So both parses draw the same conclusion.

Using graphical presentation to solve logical reasoning may refer to this method can be called a semantic network – because it solves with records of knowledge.

Comparing the Two Methodologies

In comparison of the two methods in the solving of simple logical reasoning, we are comparing the compiling of objects in the parser project or the depth, scope and simplicity of the semantic network. Both are competing methods for the PC (predicate calculus). And both methodologies are important. Ina regular scope, we definitely need a complete parser in future for the English Language – which links dictionary, thesaurus, and translators will have a universal impact. On the foundation of such, we explore the simplicity of the semantic network so that extremely complicated reasoning can be construct and evaluated in a compiling fashion that pushes AI reasoning simulation and AI consultation schemes on the fly. As we build up our blocks of knowledge and computation of the AI, we draw our attention onto the applications of which – these conclusively are in the domain of semantic networks.


This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)


About the Author

Ming Landers
Software Developer Microsoft
United States United States
I was born in China and immigrated to the United States when I was young. I went to high school, and community college locally. In 1993 I was enrolled in the Washington State University's Computer Science program and graduated in year 1996. Between 1997 to 1999, I was in their Master degree program in Collaborative Learning. Between year 2000 to 2001, I worked in a litigation company in Utah. In reenlisted to the Army and was deployed in the Iraq conflict in 2003 and received a honorable discharge in 2004. Between 2005 to 2008 I was working as a SDET in Microsoft. Since 2009 and 2010, I started to have a deeper symptom of Schizophrenia partly caused by memories of the War. I was diagnosed as to have a Schizoaffective disorder early in year 2011 and have been off work since.
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