Contents

• Liquid Language Surface
  • Supported Surface
  • Query Shape
  • Example

Liquid Language Surface

pg_liquid supports the public Liquid syntax used in the Liquid blog examples.

Supported Surface

• % comments
• .-terminated assertions and rule definitions
• one terminal ? query
• variables such as x
• _ anonymous variables
• quoted string literals
• Edge(subject, predicate, object)
• compounds like Type@(cid=..., role=...)

Query Shape

A Liquid program is:

• zero or more assertions
• zero or more query-local rules
• one terminal query

Example

Edge("alice", "knows", "bob").
Reach(x, y) :- Edge(x, "knows", y).
Reach("alice", target)?