In this step the specification for the interaction between the views and the command-chains are formalized.

Specify the parameters that each command needs in order to execute it's task. Some of the paramters are static parameters, provided in the initialization phase of the command, some are request dependent, provided in a request, others are session parameters or application parameters. Initialization parameters and request parameters can only have string values, although, they can represent a reference to other types of objects. Most important is to properly define request parameters, as these affect the JSP implementation. Parameters are defined as name-value pairs, where the name must be unique in the scope of the parameter. The name "cmd" is a reserved parameter name, in request scope, this parameter identifies the requested command-chain.

We also need to specify the information that command-chains must supply to each JSP. In this direction the information can be represented with any type of data object. Depending on the intended lifetime of an data object the data object is made available in request-, session- or application-scope. Normally the data objects in application-scope should be treated as read-only and if a command need to update such an object, the new data object should be made available in session-scope instead.