19.1 Composite Systems

Composite systems are products that consist of many types of configuration items, such as software, hardware, and documents. Figure 19-1 shows an example of a composite system. It's a network print server, consisting of a print card with various components on it. Several components on the card contain software: (1) is the program memory, which is neatly labeled with configuration information; (2) and (3) both contain pure hardware functions (logical circuits). These may, however, both be configured by the means of software, but only one of them (2) has controlled configuration. Moreover, a change in the delivery can be seen in the form of a "louse" at (4).

Figure 19-1. Composite SystemExample

Design Considerations

The architecture for a product is a design decision that determines which functionality is to be implemented in software and which in hardware. However, this distribution is likely to change during development.

Configuration Management Considerations

It's important, when handling composite systems, to make clear what is what. When software and hardware are mixed, items that should have been placed under configuration management may easily be forgotten. Each type of item must be identified separately, and deliveries must be defined for collections. This means that it's no good to place a piece of hardware with software in it under configuration management as a single configuration item. It must be placed under configuration management as a single hardware item, a single software item, and, moreover, as a delivery consisting of these two items in combination.

Identification

All configuration items in composite systems must be identified. The item type should appear from the unique identificationhardware, software, or something else. When defining conventions, consider how software identification could be related to hardware identification for items that are naturally related . It may be necessary to create proxy items to represent hardware items in a database, as hardware items cannot be placed in the database themselves . Tracing information must define which part of functionality is implemented in which parts of the system.

Storage

Deliveries consisting of hardware with embedded software are stored like hardware itemsproduced in a number of copies that are stored physically and physically released for usage.

Change Control

Careful change control is necessary for composite systems. The same processes should be employed for all configuration items in these systems, whatever the item type. It's necessary to account for emergency changes, as shown in the "louse" in the previous example. It's especially necessary to maintain tracing information to reflect functionality transferred from a hardware item to a software item, or vice versa.

Status Reporting

Status reporting should include information that is as highly integrated as possible for all types of configuration items.