A Legal-Entity who either 1) offers a Product For-Sale for an Asking-Price or 2) agrees to exchange a Product for a Sale-Price in a Sale.
(<=> (Vendor ?X)
(Or (Exists (?Sale) (Sale-Vendor ?Sale ?X))
(Exists (?For-Sale) (For-Sale-Vendor ?For-Sale ?X))
(Exists (?Potential-Sale)
(Potential-Vendor ?Potential-Sale ?X))))
(=> (Competitor ?Competitor) (Vendor ?Competitor))
(=> (Set-Of-Vendors ?Vendors)
(Forall (?X) (=> (Member ?X ?Vendors) (Vendor ?X))))
(<=> (Competitor ?Competitor)
(And (Vendor ?Competitor)
(Qua-Entity ?Competitor)
(Or (Exists (?Vendor2)
(Competitor-Of ?Competitor ?Vendor2))
(Exists (?Vendor1)
(Competitor-Of ?Vendor1 ?Competitor)))))
(<=> (Set-Of-Vendors ?Vendors)
(And (Eo-Set ?Vendors)
(Set ?Vendors)
(Forall (?X) (=> (Member ?X ?Vendors) (Vendor ?X)))))