What does the acc stand for in SQL Group Operators of Drools ?

Issue

• There are some work going on towards Enhancements for drools in JBoss community as seen here [1] .
  In the following example of SQL Group Operators section there seems to be a new word acc being introduced to the get distinct People, by location and age.

acc( $p : Person();

        [$l, $a] : distinct( $p.location, $p.age) ) // needs to support multi return value bindings

What is the acc out here ? Is it a built-in keyword or function?

[1] DroolsLanguageEnhancements