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Chapter 4. Architecture

4.1. Define Information Model
4.1.1. Validating Example Messages against Schema
4.2. Define Choreography Model
4.2.1. Validating Requirements against Choreography Model
4.2.2. Create Documentation

One of the stages within the architecture phase is to define the information model for the message types associated with the messages exchanges between the interacting participants.

This involves defining message schema for each example message. The schema could already exist and be reused, it could be based on existing schema and just need to be upgraded to support new requirements, or it may need to be defined from scratch.

An example of a schema associated with the purchasing model is the store.xsd shown here:

Once the schema has been defined, then the example messages need to be updated to reference the schema, as shown in the following BuyRequest.xml example message:

The next step in the development process is to specify a Choreography Model to implement the requirements described within the set of scenarios.

The current representation used to define Choreography Models within SAVARA is the W3C Web Service Choreography Description Language (WS-CDL). The pi4soa tools provide a WS-CDL (or choreography description) editor. Although this standard is associated with web services, it does not mean that a system specified using this standard needs to be implemented using web services. The actual WS-CDL language is used for defining the interactions between any distributed system.

The choreography description for the Purchasing example can be found in purchasing/PurchaseGoods.cdm. When the choreography editor has been launched, by double-clicking on this file within the Eclipse environment, then navigate to the Choreography Flows tab to see the definition of the purchasing process: