Maelys Datalog

examples

Example guide

Basic allow

Two requests use different backends. The policy allows a request only when its backend is trusted and it carries text; it denies requests from untrusted backends.

Try it · Compare the allow and deny answers for req-1 (trusted) and req-2 (untrusted). These are separate relations, not two values of one boolean.

1domainname/arity kind

backend/2 edb
allowed_backend/1 edb
has_text/1 edb
allow/1 idb,query
deny/1 idb,query

Policy atoms (one quoted symbol per line; runtime EDB strings need no declaration)

2policy.dlDatalog rules

allow(R) :-
    backend(R, B),
    allowed_backend(B),
    has_text(R).

deny(R) :-
    backend(R, B),
    not(allowed_backend(B)).

3edb.dlruntime facts

allowed_backend("cli_pivot")
allowed_backend("acp")
backend("req-1", "cli_pivot")
has_text("req-1")
backend("req-2", "unknown_backend")
has_text("req-2")

4queriespred("symbol", 123, true)

allow("req-1")
deny("req-1")
allow("req-2")
deny("req-2")

results

Run solve() to evaluate your queries.

●predicate●variable (Uppercase)●"symbol"●edb · idb · query●% comment·rules end with .·typed facts of arity 0 to 4