DLGP (for Datalog Plus) is a textual exchange format at once human-friendly, concise and easy to parse. CoGui provides an editor for this language with syntax highlighting and a navigator.

Switch to graphical and DLGP representation with the factory view is a good way to become familiar with the language. See section The factory view .

DLGP files can also be imported. See section Import from Datalog±

Finally, you can also export the whole project. See section Export to Datalog±


The format can be seen as an extension of the commonly used format for plain Datalog. Datalog± may define four kinds of knowledge elements: 

  • Facts
  • Existential rules
  • Negative constraints
  • Conjunctives queries


As usually in Datalog, variables begin with an upper-case letter and constants with a lower-case letter. We distinguish between regular constants(called constants hereafter) and literals, which are values belonging to some datatype. Literals are given as double-quoted strings or numeric values(integers and floats).
The file name has the extension .dlgp or .dlp. Character encoding is assumed to be UTF-8. 
Complete syntax is described in this paper: DLGP: An extended Datalog Syntax for Existential Rules and Datalog±Version 2.0 


Some examples of different elements are available here. 


Some examples


Datalog± expressions

Cogui conversion

[a_fact]fatherOf(zeus,apollo),
god(zeus), god(apollo).


Every kinds of knowledge elements can be named with simple strings .

fatherOf(<Zeus>,<Apollo>), 
god(<Zeus>), god(<Apollo>).


Zeus can not be used as a constant name in DLPG language.

belongsTo(<Zeus>,<Greek+pantheon>).


Use + symbol to represent a space in the Datalog constant name.

?:-fatherOf(X,apollo).


Is there someone father of Apollo ?

distance(athens,marathon,42.195),
town(athens),town(marathon).


A ternary predicate with a literal value(float).

distance(athens,marathon,"42km195"),
town(athens),town(marathon).


A ternary predicate with a literal value(string).

distance(athens,marathon,42)
,town(athens),town(marathon).


A ternary predicate with a literal value(int).

siblingOf(Y,X):-siblingOf(X,Y).


A rule to define a symmetric relation.

parentOf(X,Z):-parentOf(X,Y),parentOf(Y,Z).


A rule to define a transitive relation.

god(Y),human(Z),
parentOf(Y,X),parentOf(Z,X):-demigod(X).


A rule with new variables in conclusion (head of the rule).
Unlike safe clauses in classic Datalog, Datalog± accepts new variables in the rule heads.

X=Y:-equals(X,Y).

 
A rule with equality as a conclusion. 
Head (conclusion) part of the rule can contains one or more equality relations between frontier concepts. They are represented as coreference links on the cogui model.


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