Datalog - Programming language

Datalog is a programming language created in 1977.

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Datalog is a declarative logic programming language that syntactically is a subset of Prolog. It is often used as a query language for deductive databases. In recent years, Datalog has found new application in data integration, information extraction, networking, program analysis, security, and cloud computing. Read more on Wikipedia...

Datalog Wikipedia page
Datalog first developed in University of Maryland
Explore Datalog snippets on Rosetta Code
Datalog on HOPL
See also: (14 related languages)Prolog, Java, OWL, C, Python, Ruby, Lua, Clojure, Racket, Tcl, Haskell, .QL, RDF, SPARQL
Read more about Datalog on the web: 1. 2. 3.

Example from the web:

parent(john, douglas). % store some data
parent(john, douglas)? % run a query

Example from Wikipedia:

ancestor(X,Y) :- parent(X,Y).
 ancestor(X,Y) :- parent(X,Z),ancestor(Z,Y).

Language features

Feature	Supported	Token	Example
Comments	✓		% A comment
Line Comments	✓	%	% A comment
Semantic Indentation	X