is a bit 'cheating' as TMQL PEs and TMRM PEs are quite similar
"give me all cities in which there happens a conference"
// city [ . <- location -> event * = conference ]
# expanding shortcuts = (%_) [ @_[0] classes :>: = city ] [ @_[0] players :<: location players :>: event classes :>: = conference ] # transforming into TMRM PEs ( {{%_}} ) . if ( pi_0 {{ classes :>: }} === city ) then epsilon else () . if ( ..... ) then epsilon else ()
AND, & between PE predicates -> [...] . [...]
OR, | between PE predicates -> [ .... ||| .... ]
NOT in PE predicate -> swap then and else branch
= between PEs -> [ .... === .... ]