Description: Define the relations
class. Proper class relations (like I, see
reli 5839) are not elements of it. The element of this
class and the
relation predicate are the same when 𝑅 is a set (see elrelsrel 38469).
The class of relations is a great tool we can use when we define classes
of different relations as nullary class constants as required by the 2.
point in our Guidelines https://us.metamath.org/mpeuni/mathbox.html 38469.
When we want to define a specific class of relations as a nullary class
constant, the appropriate method is the following:
1. We define the specific nullary class constant for general sets (see
e.g. df-refs 38492), then
2. we get the required class of relations by the intersection of the class
of general sets above with the class of relations df-rels 38467 (see
df-refrels 38493 and the resulting dfrefrels2 38495 and dfrefrels3 38496).
3. Finally, in order to be able to work with proper classes (like
iprc 7934) as well, we define the predicate of the
relation (see
df-refrel 38494) so that it is true for the relevant proper
classes (see
refrelid 38504), and that the element of the class of the
required relations
(e.g. elrefrels3 38501) and this predicate are the same in case of
sets (see
elrefrelsrel 38502). (Contributed by Peter Mazsa,
13-Jun-2018.) |