代写COMP4418、代做Java、c++编程设计、代写Python、代做programming

日期：2019-10-09 10:52

COMP4418, 2019–Assignment 1

Due: 23:59:59pm Sunday 13 October (End of Week 4)

Late penalty: 10 marks per day.

Worth: 15%.

This assignment consists of four questions. The first two questions and the fourth question require

written answers only. The third question requires some programming and a written report.

1. [20 Marks] (Logical Inference)

For each of the following inferences:

(a) prove whether or not the following inferences hold using a suitable semantic method (|=); and,

(b) prove whether or not the following inferences hold syntactically using resolution (`).

In each case you must provide a proof and clearly state whether the inference holds or whether the

inference does not hold.

(i) p ∧ (q ∨ r)[|= / `](p ∧ q) ∨ (p ∧ r)

(ii) [|= / `]p → (q → p)

(iii) ∃x.∀y.Likes(x, y)[|= / `]∀x.∃y.Likes(x, y)

(iv) ¬p → ¬q, p → q[|= / `]p ↔ q

(v) ∀x.P(x) → Q(x), ∀x.Q(x) → R(x), ¬R(a)[|= / `]¬P(a)

2. [20 Marks] (Logic Puzzle)

Flatmates, from Logic Problems, Issue 10, page 35. The following logic puzzle appears in the lecture

notes and is solved using Prolog. Here we will determine a solution and argue using interpretations

as explained in lectures. Six people live in a three-storey block of studio flats laid out as in the

plan.

Flat 5 Flat 6

Flat 3 Flat 4

Flat 1 Flat 2

• Ivor and the photographer live on the same floor.

• Edwina lives immediately above the medical student.

• Patrick, who is studying law, lives immediately above Ivor, and opposite the air hostess.

• Flat4 is the home of the store detective.

• Doris lives in Flat2.

• Rodney and Rosemary are 2 of the residents in the block of flats.

• One of the residents is a clerk.

(i) Represent these facts as sentences in first-order logic.

(ii) From the clues given, work out the name and situation of the resident of each flat. Using your

formalisation in part (2a), is it possible to determine the name and situation of the resident

of each flat? Show semantically how you determined your answer.

(iii) If your answer to part (2b) was ‘no’, indicate what further sentences you would need to add

to your formalisation so that name and situation of the resident of each flat.

3. [50 Marks] (Automated Theorem Proving)

In 1958 the logician Hao Wang implemented one of the first automated theorem provers. He

succeeded in writing several programs capable of automatically proving a majority of theorems

from the first five chapters of Whitehead and Russell’s Principia Mathematica (in fact, his program

managed to prove over 200 of these theorems “within about 37 minutes, and 12/13 of the time

is used for read-in and print-out”). This was an impressive achievement at the time; previous

attempts had only succeeded in proving a handful of the theorems in Principia Mathematica.

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Background

Wang’s idea is based around the notion of a sequent (this idea had been introduced years earlier

by Gentzen) and the manipulation of sequents. A sequent is essentially a list of formulae on either

side of a sequent (or provability) symbol `. The sequent π ` ρ, where π and ρ are strings (i.e.,

lists) of formulae, can be read as “the formulae in the string ρ follow from the formulae in the

string π” (or, equivalently, “the formulae in string π prove the formulae in string ρ”).

To prove whether a given sequent is true all you need to do is start from some basic sequents and

successively apply a series of rules that transform sequents until you end up with the sequent you

desire. This process is detailed below.

Additionally, determining whether a formula φ is a theorem, is equivalent to determining whether

the sequent ∅ ` φ is true (e.g., ` ¬φ ∨ φ).

Formulae

Connectives

We allow the following connectives in decreasing order of precedence:

¬ — negation

∧ — conjunction; ∨ — disjunction (both same precedence)

→ — implication; ↔ — biconditional (both same precedence).

Formula

• A propositional symbol (e.g., p, q, . . .) is an atomic formula (and thus a formula).

• If φ, ψ are formulae, then ¬φ, φ ∧ ψ, φ ∨ ψ, φ → ψ, φ ↔ ψ are formulae.

Sequent

If π and ρ are strings of formulae (possibly empty strings) and φ is a formula, then π, φ, ρ is a

string and π ` ρ is a sequent.

Rules

The logic consists of the following sequent rules. The first rule (P1) gives a characterisation of

simple theorems. The remaining rules are simply ways of transforming sequents into new sequents.

The manner in which you can construct a proof for a sequent to determine whether it holds or not

is given below.

P1 Initial Rule: If λ, ζ are strings of atomic formulae, then λ ` ζ is a theorem if some atomic

formula occurs on both side of the sequent `.

In the following ten rules λ and ζ are always strings (possibly empty) of formulae.

P2a Rule ` ¬: If φ, ζ ` λ, ρ, then ζ ` λ, ¬φ, ρ

P2b Rule ¬ `: If λ, ρ ` π, φ, then λ, ¬φ, ρ ` π

P3a Rule ` ∧: If ζ ` λ, φ, ρ and ζ ` λ, ψ, ρ, then ζ ` λ, φ ∧ ψ, ρ

P3b Rule ∧ `: If λ, φ, ψ, ρ ` π, then λ, φ ∧ ψ, ρ ` π

P4a Rule ` ∨: If ζ ` λ, φ, ψ, ρ, then ζ ` λ, φ ∨ ψ, ρ

P4b Rule ∨ `: If λ, φ, ρ ` π and λ, ψ, ρ ` π, then λ, φ ∨ ψ, ρ ` π

P5a Rule `→: If ζ, φ ` λ, ψ, ρ, If ζ, φ ` λ, ψ, ρ, then ζ ` λ, φ → ψ, ρ

P5b Rule →`: If λ, ψ, ρ ` π and λ, ρ ` π, φ, then λ, φ → ψ, ρ ` π

P6a Rule `↔: If φ, ζ ` λ, ψ, ρ and ψ, ζ ` λ, φ, ρ, then ζ ` λ, φ ↔ ψ, ρ

P6b Rule ↔`: If φ, ψ, λ, ρ ` π and λ, ρ ` π, φ, ψ, then λ, φ ↔ ψ, ρ ` π

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Proofs

The basic idea in proving a sequent π ` ρ is to begin with instance(s) of Rule P1 and successively

apply the remaining rules until you end up with the sequent you are hoping to prove.

For example, suppose you wanted to prove the sequent ¬(p ∨ q) ` ¬p. One possible proof would

proceed as follows.

1. p ` p, q Rule 1

2. p ` p ∨ q Rule P4a

3. ` ¬p, p ∨ q Rule P2a

4. ¬(p ∨ q) ` ¬p Rule P2b

QED.

However, a simpler idea (as it will involve much less search) is to begin with the sequent(s) to be

proved and apply the rules above in the “backward” direction until you end up with the sequent

you desire. In the example then, you would begin at Step 4 and apply each of the rules in the

backward direction until you end up at Step 1 at which point you can conclude the original sequent

is a theorem.

Question Specification

In this assignment you are to emulate Hao Wang’s feats and implement a propositional theorem

prover. You may use any programming language to complete this question. You must provide

a script named assn1q3 or a Makefile that, when the command make is executed, produces an

executable file assn1q3.

Input

The input will consist of a single sequent on the command line. Sequents will be written as:

[List of Formulae] seq [List of Formulae] To construct formulae, atoms can be any string of

characters (without space) and connectives as follows:

• ¬: neg

• ∧: and

• ∨: or

• →: imp

• ↔: iff

So, for example, the sequent p → q, ¬r → ¬q ` p → r would be written as:

[p imp q, (neg r) imp (neg q)] seq [p imp r]

Your program should be called assn1q3 and run as follows:

./assn1q3 ’Sequent’

For example

./assn1q3 ’[p imp q, (neg r) imp (neg q)] seq [p imp r]’

Output

The first line of the output will be either true or false indicating whether or not the sequent on

the command line holds. This output is worth 40% of the total mark for this question on given

and hidden test data. The subsequent lines of output should produce a proof like the one in the

Proofs section above.

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Marking for this Question

• Code: 40%

• Given test data: 20%

• Hidden test data: 20%

• Printing proofs: 20%

References

[1] Hao Wang, Toward Mechanical Mathematics, IBM Journal for Research and Development,

volume 4, 1960. (Reprinted in: Hao Wang, ”Logic, Computers, and Sets”, Sciene Press, Peking,

1962. Hao Wang, ”A Survey of Mathematical Logic”, North Holland Publishing Company, 1964.

Hao Wang, ”Logic, Computers, and Sets”, Chelsea Publishing Company, New York, 1970.)

[2] Alfred North Whitehead and Bertrand Russell, Principia Mathematica, 2nd Edition, Cambridge

University Press, Cambridge, England, 1927.

A List of 10 Propositional Theorems

You may find it instructional to prove these by hand first.

(i) ` ¬p ∨ p

(ii) ¬(p ∨ q) ` ¬p

(iii) p ` q → p

(iv) p ` p ∨ q

(v) (p ∧ q) ∧ r ` p ∧ (q ∧ r)

(vi) p ↔ q ` ¬(p ↔ ¬q)

(vii) p ↔ q ` (q ↔ r) → (p ↔ r)

(viii) ` (¬p ∧ ¬q) → (p ↔ q)

(ix) p ↔ q ` (p ∧ q) ∨ (¬p ∧ ¬q)

(x) p → q, ¬r → ¬q ` p → r

4. [10 Marks] (Knowledge Representation and Reasoning)

Select a method for knowledge representation and reasoning that we have not covered in lectures

and provide one example that explains:

(i) how the method represents knowledge;

(ii) describes how inference works for reasoning with that knowledge representation.

In answering this question some sources you might consult include:

• Ronald Brachman and Hector Levesque, Knowledge Representation and Reasoning, Morgan

Kaufmann, 2004.

• Stuart Russell and Peter Norvig, Artificial Intelligence: A Modern Approach, Third Edition,

Prentice Hall, 2010.

• The Principles of Knowledge Representation and Reasoning conference series (www.kr.org).

• The Association for the Advancement of Artificial Intelligence conference series (www.ijcai.org).

• The International Joint Conference on Artificial Intelligence series (www.aaai.org).

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Assignment Submission

You will need to submit answers to Questions 1, 2, 4 and the report for Question 3 in a PDF file

named assn1.pdf along with any source code files for Questions 3. Your report for Question 3 in

assn1.pdf should describe the additional files you submit for this question and how they can used to

replicate/generate your results.

give cs4418 assn1 assn1.pdf assn1-q3-files

The deadline for this submission is 23:59:59am Sunday 13 October.

Late Submissions

In case of late submissions, 10% will be deducted from the maximum mark for each day late.

No extensions will be given for any of the assignments (except in case of illness or misadventure).

Read the course outline carefully for the rules regarding plagiarism.

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