UML Sequence Diagrams

During the requirements analysis phase, the system can be treated as a single "black box", which means that we can look at the system's behavior (what it does) without explaining how it does it. Read this section to see an example of a simplified trace diagram that shows only system input events. This is called a system sequence diagram.

12. Documenting Contracts

Suggested schema by Liu, for presenting a contract is as shown in Table 3.11:

Table 3.11: Schema for Documenting a Contract of a System Operation

Name	Name of a system operation and parameters
Responsibilities	A short description of the responsibility the operation
Type	Name of type (concept, software class, interface)
Cross References S	System function reference numbers, use cases, etc
Note	Design notes, algorithms, and so on

Exceptions	Exceptional cases
Output	Non-User Interface (UI) outputs, such as messages or records that are sent outside of the system
Pre-conditions	The conditions that the state of the system is assumed to satisfy before the execution of the operation
Post-conditions	Describes changes in the state of objects in the domain area. The sate changes can include: instances creation, associations formed or deletion and attributes changed.