What do these characters mean in RDF/OWL Domain and Range logic?

Question

Does someone know what these strange looking characters are? I would like to learn what they mean. Can you send me a reference/hyperlink so I can understand what they mean?

http://www.w3.org/TR/2004/REC-owl-semantics-20040210/rdfs.html#owl_ObjectProperty_rdf

Answer 1

These are just operators from set theory: ⊆ is 'subset', ∅ and {} are the empty set, ≠ is 'not equals to', and ∈ is 'is an element of'. So

IOXP ⊆ $P_I$

just means "the set we call IOXP is a subset of the set we call $P_I$", and

$S_I$("l"^^d) ∈ $LV_I$

means "the URI reference denotation for URI reference "l"^^d is an element of $LV_I$".