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SysML Requirements Modeling
Requirements engineering is a fundamental aspect of a systems engineering model. The discipline focuses on eliciting, analyzing and managing customer requirements early in the process. Once the requirements are understood, trade studies can be conducted to formally assess design options, typically using weighted choices. The requirements are managed as first class citizens and are formally allocated to development items and verification methods.
Enterprise Architect has extensive functionality to assist the modeler with every aspect of the requirements engineering discipline, including elicitation, modeling, management and testing. High quality engineering documentation can be generated out-of-the-box using a wide range of built-in templates, carefully crafted to extract the information in the models and present it in visually compelling and high quality documentation in a wide range of formats, including docx, pdf and html. The documentation engine is highly configurable, and documentation to match any engineering or organizational standard can be generated by creating templates and setting generation options.
The SysML Requirements Model provides the system requirements, the expected abstract behavior and the operating constraints that the designed system must conform to. This diagram shows an example requirements model for a Portable Audio Player.
This example displays several top level requirements such as 'Ease of Use' and then breaks those requirements down into more refined requirements such as the 'Graphical User Interface'.
Building the Requirements Model
Enterprise Architect provides comprehensive support for requirements modeling, particularly through the Specification Manager, which you can use to: display existing model diagram elements in text format; edit sets of new requirements imported from a document, spreadsheet or Requirements Management tool; or create new requirement elements from scratch, building them up from text entries.
You can also generate a starter SysML Requirements model from templates supplied in the Model Wizard (). These include:
- One Level Requirement Hierarchy
- Two Level Requirement Hierarchy
- Composite Requirement Hierarchy
- Requirements Traceability
Select the 'Model Patterns' tab and the 'SysML Perspective', then scroll to and expand the 'SysML 1.5 Requirements Diagrams' Pattern group. When you click on a Pattern name in the left hand panel of the Model Wizard, a full description of what the panel provides is displayed in the right hand panel.
Elements
The main elements that can appear in Requirement diagrams are:
- Requirement
- Test Case
The Requirement elements contain two Tagged Values that you can set to be displayed on the diagram, using > Show Element Compartments > Tags.
- ID - the element or reference name of the Requirement
- Text - the description of the Requirement (its definition, purpose or, if at the top of a hierarchy of Requirements, the generic term for the group)
Connectors
The main connectors that can appear in Requirement diagrams are:
- Containment
- Trace
- Copy
- Derive
- Verify
- Refine
- Satisfy
Notes
- The standard Enterprise Architect Requirement-type is interchangeable with the SysML requirements, meaning that the general Requirement Management features such as the Specification Manager, the Traceability view and Relationship Matrix can all be used in SysML Requirements Management
- With the Copy connector, when there is a value in the 'Text' Tagged Value on the target Requirement, the text is copied to the 'Text' Tagged Value on the source Requirement; the source 'Text' Tagged Value is set to read-only