Abstract: In a system that provides an open exchange environment to connect business entities through a network, methods, systems, and apparatus, including computer program products, for enabling a first of the business entities to specify global constraint information; and identifying, at least in part on the global constraint information, a set of business entities eligible to participate in a transaction with the first of the business entities, the transaction involving an online advertisement space or an online advertisement creative that is associated with the first of the business entities.