Definition df-rels 38887

Description: Define the relations class. Proper class relations (like I, see reli 5792) are not elements of it. The element of this class and the relation predicate are the same when 𝑅 is a set (see elrelsrel 38889).

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 38889. 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 39037), 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 38887 (see df-refrels 39038 and the resulting dfrefrels2 39040 and dfrefrels3 39041).

3. Finally, in order to be able to work with proper classes (like iprc 7881) as well, we define the predicate of the relation (see df-refrel 39039) so that it is true for the relevant proper classes (see refrelid 39049), and that the element of the class of the required relations (e.g. elrefrels3 39046) and this predicate are the same in case of sets (see elrefrelsrel 39047). (Contributed by Peter Mazsa, 13-Jun-2018.)

Assertion

Ref	Expression
df-rels	⊢ Rels = 𝒫 (V × V)

Detailed syntax breakdown of Definition df-rels

Step	Hyp	Ref	Expression
1		crels 38632	. 2 class Rels
2		cvv 3448	. . . 4 class V
3	2, 2	cxp 5638	. . 3 class (V × V)
4	3	cpw 4549	. 2 class 𝒫 (V × V)
5	1, 4	wceq 1554	1 wff Rels = 𝒫 (V × V)

This definition is referenced by:  elrels2  38888