OQL:

OQL:

select distinct h.name

from c in Cities,

h in c.hotels,

p in c.places_to_visit

where c.name=“Arlington”

and h.name=p.name

Monoid comprehension:

?{ h.name | c ? Cities,

h ? c.hotels,

p ? c.places_to_visit,

c.name=“Arlington”,

h.name=p.name }

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Here I have the same OQL query and its translation to the monoid comprehension calculus. I will present the calculus in detail shortly. The union symbol indicates that the result will be a set.