What is logical programming?

Logic programming is a programming paradigm based on formal logic. A program is described as a set of facts and rules, rather than as a sequence of instructions to execute.

Main concepts:

• Facts: Assertions that are considered true (e.g., parent(ivan, petr)).
• Rules: Descriptions of dependencies between facts (e.g., grandfather(X, Y) :- parent(X, Z), parent(Z, Y), read as "X is the grandfather of Y if X is the parent of Z, and Z is the parent of Y").
• Queries: Questions posed to the program to obtain information (e.g., ?- grandfather(ivan, Who?), "Who is Ivan's grandson?").

The execution process of the program reduces to finding a proof of the truth of the query based on the given facts and rules using inference mechanisms (e.g., resolution).

The most well-known logic programming language is Prolog.

Application in QA:

• Specification of requirements in logical form.
• Automatic generation of tests based on specifications.
• Analysis of constraints and dependencies within the system.
• Formal verification of system properties.

Example in Prolog:

// Facts
parent(ivan, petr).
parent(petr, anna).
parent(ivan, maria).

// Rules
grandfather(X, Y) :- parent(X, Z), parent(Z, Y).

// Query
// ? - grandfather(ivan, Who?).
// Answer: Who = anna.