Analyzing Interactions › Defining Entity Views › Defining Group Views

Defining Group Views

The views for the Take Order Process do not completely show the structure of the data. In the original description of the Take Order process, it was clear that multiple products could be ordered on a single order. The import view must therefore allow for multiple occurrences of product for its Number and order item for Quantity. This is accomplished by using a repeating group view.

A group view is strictly defined as a collection of one or more entity views. A group view is the only kind of view that may be designated as repeating. So, any time a process imports or exports a list of entities, the list is included as a repeating group view.

To complete the views for Take Order, you must add a group view to which the entity views Import product and Import order item will belong.

The following tables show the finished views for Take Order. Notice that the letter "r" precedes the group view Import Product Information indicating a repeated group view.

CA Gen can capture the following details about group views:

• Name
• Description
• Cardinality
• Minimum cardinality
• Maximum cardinality
• Average cardinality
• Optionality (import views only)
• Method of subscripting

Group views may not appear in the entity action views for a process.

Name

Each group view name should accurately reflect its contents. Unlike entity view names, group view names always stand alone in the detailed process logic, so they should specify the role of their elements, for example, input, update, and output.

This explains the name Import Product Information in the table previous table rather than simply Product Information.

Description

In CA Gen, the description for a view of any kind is optional. It is necessary only when the purpose of the view is not clear from its name.

Cardinality

Cardinality indicates whether the group view repeats. The cardinality may be:

• One (non-repeating)
• One or more (repeating)

In practice, detailed process logic never needs to reference non-repeating group views. Instead, it references their entity views. The analyst and business person may, however, name a group of entity views to provide clear documentation about parts of the data that are used together.

For each repeating group view, you must also specify the following information that will be used in the design and construction of a system:

• Minimum cardinality—The least number of occurrences it can contain
• Maximum cardinality—The greatest number of occurrences it can contain
• Average cardinality—The average number of occurrences it can contain

For minimum and maximum cardinality, you may indicate whether the value specified is an estimate—there will probably never be more than ten or an absolute limit—there must never be more than ten.

Optionality

You may specify optionality for import views only.

• Mandatory group views
• If an import group view is specified as mandatory, each element specified as mandatory must have a value when the process to which the view belongs begins execution. For example, in the following table, Group View 1 consists of Group View 2 and Entity View 3.

• If Group View 1 is mandatory, then Group View 2 is also mandatory. All mandatory attributes that appear in all its entity views are also mandatory. So the mandatory attributes of Entity View 3 must have values when the process to which Group View 1 belongs begins to execute.
• Optional group views
• For an optional group view, you may specify the optionality condition in the same way as the optionality conditions for attributes or relationship memberships. This condition is stored as part of the group view description.

Subscripting

Subscripting is the means by which a particular occurrence of an element of a repeating group view is identified by a statement in an Action Diagram.

Each repeating group view, that is, a group view with a cardinality of one or more, must be defined as either implicitly or explicitly subscripted.

In design, repeating group views are usually handled using implicit subscripting because this gives better control of selection within a group.

In analysis, implicit subscripting is sufficient for the handling of repeating group views.

A process must set values for explicit subscripts; only in very complex process logic is there a need for explicit subscripting. Subscripting can be changed to explicit during system design if necessary.