The current query language is a bit awkward, but functional:
-query ::= complex | simple | attr query.
-complex ::= operator query query.
+query ::= ['@attrset' <attribute-set>] rpn
+rpn ::= complex | simple | attr rpn
+complex ::= operator rpn rpn
operator ::= '@and' | '@or' | '@not'.
simple ::= term | set.
term ::= <word> | '"' <term> ... '"'.
set ::= '@set' <setname>.
-attr ::= '@attr' <number> '=' <number>.
+attr ::= '@attr' [<attribute-set>] <number> '=' <number>.
Eg.:
@and @attr 1=1 andersen @attr 1=4 @attr 4=2 duckling
+@attrset Bib-1 @and @attr GILS 2=2008 Washington @attr 1=21 weather
+
The directories:
doc - Documentation.