27. A computer-usable medium having computer-readable program code embodied therein for causing a computer to perform a method of communicating data within a network of peer-to-peer enterprise information systems, said method comprising: mapping entities within a unified entity-relationship system to entities within subsumed entity-relationship systems; implementing user-specified relationships between mapped entities to generate a unified entity-relationship model; publishing a data change of an attribute of a first entity stored on a first source system, wherein said first entity is one of said entities within said subsumed entity-relationship systems; and using said global attribute object model, comprising a first mapped relationship, in conjunction with a join model for enforcing data consistency within said network by: forming, by said join engine peer, a second entity from a set of related entities, wherein at least one of said set of related entities is obtained from a second source system; and using said first mapped relationship to enforce said data consistency between said first entity and said second entity; and storing said data change in said second entity on a third source system.
27. A computer-usable medium having computer-readable program code embodied therein for causing a computer to perform a method of communicating data within a network of peer-to-peer enterprise information systems, said method comprising: mapping entities within a unified entity-relationship system to entities within subsumed entity-relationship systems; implementing user-specified relationships between mapped entities to generate a unified entity-relationship model; publishing a data change of an attribute of a first entity stored on a first source system, wherein said first entity is one of said entities within said subsumed entity-relationship systems; and using said global attribute object model, comprising a first mapped relationship, in conjunction with a join model for enforcing data consistency within said network by: forming, by said join engine peer, a second entity from a set of related entities, wherein at least one of said set of related entities is obtained from a second source system; and using said first mapped relationship to enforce said data consistency between said first entity and said second entity; and storing said data change in said second entity on a third source system. 28. The computer-usable medium as described in claim 27 wherein said second plurality of entities are mapped by automatically importing schemas of databases for said entities into said global attribute object model and correlating relationships between related entities.