Prolog Programming Language - Artificial intelligence:

Most of the programming languages are procedural: the programmer specifies exactly the correct instructions (algorithms) required to get an agent to function correctly. It wonders for many people that there is another way to write programs. Program is declarative programming when the user declares what the output to a function should look like given some information regarding the input. The agent then searches for an answer which fits the declaration, and returns any it finds.

As an instance, suppose a parent asking their child to run to the shop and buy some groceries. To do this in a declarative fashion,in simple manner, the parent needs to write shopping list. The parents have "programmed" their child to perform their work in the knowledge that the child has underlying search routines which will enable her orhim to get to the shop, find and buy the groceries, and later come home. To instruct their child in a procedural fashion, they would need to tell the child to go out of the front door, turn right, walk down the street, stop after 60 steps, and so on.

We see that declarative programming languages may have some advantages over procedural ones. Actually, it is often said that a Java program written to do the same as a Prolog program typically takes about 10 times the number of lines of code. Many Artificial Intelligence researchers try out an idea in Prolog before implementing it more completely in other languages; because Prolog may be used to perform searches in simple way (see later).

A well-known declarative language which is used many times by Artificial Intelligence researchers is Prolog, which is centred on first-order logic. For any specific declarative programming language, the 2 most important aspects are: how information is denoted, and the underlying search routines upon which the language is based. Robert Kowalski put this in the most succinct way:

Algorithm = Control +Logic