3.4.1 The ebXML Business Collaboration

The ebXML Business Collaboration is the realisation of a business process. The realisation is modelled in UML and converted to XML. The main parts of a business collaboration are:

1. Business Collaboration
   A Business Collaboration is a set of Business Transactions between business partners. Each trading partner plays one or more roles in the collaboration. There are two different Business Collaborations: The Binary Collaboration and the Multiparty Collaboration. In the Binary Collaboration there are only two trading partners involved. In a Multiparty Collaboration there are more than two trading partners involved. But a Multiparty Collaboration is synthesised from two or more Binary Collaborations.

   A Binary Collaboration has several Business Activities. A Business Activity itself can be another Binary Collaboration (for recursion) or a concrete Business Transaction Activity.

2. Business Transaction

   A Business Transaction Activity is basically a concrete Business Transaction. A Business Transaction takes place between two trading parters which play the opposite role, e.g. the ``buyer'' role and the ``seller'' role. A Business Transaction always has a requesting role and a responding role. It is important to mention, that a Business Transaction always fails or succeeds. The Business Transaction has Business Documents attached to it.

3. Business Document flows
   As seen above, the Business Transaction has always two roles. The requesting role has one Business Document. The responding role may not have a Business Document e.g. a one-way notification has no responding Business Document. The structure of the Business Document itself is defined somewhere else. Of course ebXML reuses the Core Components (see later chapter for Core Components) or so called Business Information Objects from a Core Component Library to create the Business Documents.

4. Choreography
   It is important to notice, that a Business Collaboration between two trading partners can have several Business Transactions (Business Activities). The Choreography defines the sequence of the Business Transactions. The Choreography is realised by a transition between two Business Transactions. A transition has guards associated with it. Choreographies are modelled by UML Activity Diagrams.

5. Patterns
   Patterns are a set of predefined transaction interactions. Patterns are discovered commonalities. The ebXML E-Commerce Patterns document [10] explains more.

An example Business Process illustrates these parts: Company A provides a standardised catalogue to company B. Company B checks for the required product and asks company A if the required goods are deliverable. Depending on the answer, company B requests an offer and company A sends an offer for the requested quantity of product X to company B. Company B accepts the offer and sends an order back to company A. Company A confirms the order and starts the shipment of the goods. Company A sends a shipment notification to company B including the bill. Company B gets the goods and pays the bill. This example scenario is easy and complex at the same time.

As noted above the Business Process Specifications are modelled with a UML class diagram (see figure 9 for the class diagram). In the class diagram we can see how the realisation of the main parts of a Business Collaboration are realised. A closer look at the class diagram helps understanding of how a Business Collaboration is built in detail.