Definition df-rels 38778

Description: Define the relations class. Proper class relations (like I, see reli 5776) are not elements of it. The element of this class and the relation predicate are the same when 𝑅 is a set (see elrelsrel 38780).

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 38780. 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 38928), 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 38778 (see df-refrels 38929 and the resulting dfrefrels2 38931 and dfrefrels3 38932).

3. Finally, in order to be able to work with proper classes (like iprc 7856) as well, we define the predicate of the relation (see df-refrel 38930) so that it is true for the relevant proper classes (see refrelid 38940), and that the element of the class of the required relations (e.g. elrefrels3 38937) and this predicate are the same in case of sets (see elrefrelsrel 38938). (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 38523	. 2 class Rels
2		cvv 3430	. . . 4 class V
3	2, 2	cxp 5623	. . 3 class (V × V)
4	3	cpw 4542	. 2 class 𝒫 (V × V)
5	1, 4	wceq 1542	1 wff Rels = 𝒫 (V × V)

This definition is referenced by:  elrels2  38779