Requirement Links

Track how your requirements relate to your model design by usingRequirements Toolbox™to create links between your requirements and various Simulink^®model elements, including blocks, Stateflow^®objects,Simulink Test™test objects, Simulink data dictionary entries, MATLAB^®code lines, and other requirements.

Each link has a correspondingslreq.Linkobject. The link points from asource itemto adestination item.

You can create links to blocks and Stateflow objects from the Simulink Editor by dragging requirements from theRequirements Browserin the Requirements Perspective View. You can create links toSimulink Testtest objects from the Test Manager or from theRequirements Editor. For more information on linking Simulink model elements to requirements, seeLink Blocks and RequirementsandLink to Test Cases from Requirements.

Requirement links identify the requirement by the Session Independent Identifier (SID) instead of the Custom ID, such that the link remains functional if the Custom ID is modified.

Linkable Items

You can create links between these requirements items, model entities, test artifacts, and code:

Requirements Toolboxobjects:
- slreq.Requirementobjects
- slreq.Referenceobjects
- slreq.Justificationobjects
Simulink entities:
- Blocks
- Subsystems
Simulink data dictionary entries
Stateflow objects:
- States
- Charts and subcharts
- Transitions
System Composer™ architecture entities:
- Components
- Ports
- Views
Simulink Testobjects:
- Test files
- Test suites
- Test cases
- Iterations
- Assessments
Lines of MATLAB code in:
- MATLAB.mfiles.
- MATLAB Function blocks. For more information, seeIntegrate Basic Algorithms Using MATLAB Function Block(Simulink).
- MATLAB-based Simulink tests. For more information, seeTest Models Using MATLAB-Based Simulink Tests(Simulink Test).

You can set external artifacts like URLs as link destinations by creating MATLAB structures. There are two approaches available:

Create a link destination structure, then create a link between the requirement and the destination.

myLinkDest = struct('domain','linktype_rmi_url','artifact',...'//www.tatmou.com/nl/','id','') myLinkDest = structwithfields:domain:'linktype_rmi_url'artifact:'www.tatmou.com'id:''slreq.createLink(myReq, myLinkDest);

Create a requirement links data structure usingrmi('createempty'). Seermi.

Link Types

Each link has a type that describes the relationship between the source and destination items. The link type refers to theslreq.Linkobject'sTypeproperty value.

Each link type has an intended use case. For example, theImplementlink type indicates a relationship between a requirement and a design item that implements the requirement. When you create a link between two items,Requirements Toolboxsets the link type and designates the items as source or destination depending on the type of artifact that they belong to. For example, if you create a link between a requirement and a Simulink model element,Requirements Toolboxassumes that the model element implements the requirement. It sets the link type toImplementand designates the model element as the source and the requirement as the destination.

If there is no assumed link type for a link created between two items, thenRequirements Toolboxsets the link type toRelate.

After you create the link, you can edit the link type in theRequirements Editor, the Requirements Perspective, or at the MATLAB command line. In theRequirements Editor, clickShow Links. Select a link and, in theDetailspane, underProperties, select the desired link type from theTypelist.

Requirements Toolboxprovides six built-in link types.

The forward direction indicates how the source relates to the destination. Similarly, the backward direction indicates how the destination relates to the source.

Type	Description	Source-to-Destination Example	Forward Direction	Backward Direction
`Relate`	General relationship between items for most use cases Bi-directional link	Requirement to requirement	The first requirement isrelated tothe second requirement.	The second requirement isrelated tothe first requirement.
`Implement`	Specifies the source item that implements the requirement Contributes to the implementation status For more information, seeReview Requirements Implementation Status.	Simulink model element to requirement	The Simulink model elementimplementsthe requirement.	The requirement isimplemented bythe Simulink model element.
`Verify`	Specifies which source item verifies the requirement Contributes to the verification status if the source item is one of the accepted item types For more information, seeReview Requirements Verification Status.	Simulink test case to requirement	The Simulink test caseverifiesthe requirement.	The requirement isverified bythe Simulink test case.
`Derive`	Specifies which source item derives the destination item	Importedreferenced requirementto requirement	The imported referenced requirementderivesthe requirement.	The requirement isderived fromthe imported referenced requirement.
`Refine`	傅指定哪个源项添加细节nctionality specified by the destination item	Low-level requirement to high-level requirement	The low-level requirementrefinesthe high-level requirement.	The high-level requirement isrefined bythe low-level requirement.
`Confirm`	Specifies a relationship between a requirement and an external test result source Can contribute to the verification status in certain cases For more information, seeInclude Results from External Sources in Verification Status.	Requirement to external test result	The requirement isconfirmed bythe external test result.	The external test resultconfirmsthe requirement.

TheImplementandVerifylink types describe requirement-to-model and requirement-to-test relationships. Specify the source and the destination artifacts carefully because these links affect the implementation status and verification status. For more information, seeReview Requirements Implementation StatusandReview Requirements Verification Status.

The link type also affects the impact direction in the Traceability Diagram window. For more information, seeVisualize Links with a Traceability Diagram.

Custom Link Types

除了内置类型,您可以定义custom link types. Custom link types must be a subtype of one of the built-in types. The custom link type inherits some functionality from the built-in type, including how the link type contributes to the implementation and verification statuses. For more information, seeDefine Custom Requirement and Link Types.

Review Requirement Links

You can review links in theRequirements Editoror the Requirements Browser. To view links in theRequirements Editor, clickShow Links. To view links in the Requirements Browser, selectLinksfrom theViewdrop-down menu.

When working in the Simulink Editor, you can review requirement links for individual requirements. In the Requirements Browser, selectRequirementsfrom theViewdrop-down menu and select a requirement. The links are displayed in the Property Inspector, underLinks.

By default, all the outgoing links from a source artifact are stored in a Link Set file (.slmx). SeeRequirements Link Storagefor more information on requirements links storage.

When you delete a link, all related data is deleted including associated comments and custom attributes.

Resolve Links

For a link to be resolved, you must be able to navigate to the source item and to the destination item. If the source, destination, or both are not available, the link is unresolved. The source or destination items can be unavailable because:

The design artifact that contains the source or destination item is not loaded. For example, if you load a requirement set that has incoming links from a Simulink model, this also loads the link set that belongs to the model. However, if you do not load the Simulink model, the links are unresolved because the link sources are not available.
The design artifact loaded, but the specified ID does not exist. For example, if you delete a linked requirement, the link becomes unresolved because the stored ID no longer corresponds to a valid item.

If a link is unresolved because the specified ID does not exist, it is a broken link.

To see the unresolved links, in theRequirements Editor, clickShow Links. Unresolved links are denoted by.

If a link is unresolved because the source or destination is not loaded, you can resolve the link by loading the file that contains the unloaded source or destination. If a link is broken, you can use thesetSourceandsetDestinationmethods to repair the link.

Load Link Information

For artifacts such as requirement sets, Simulink models, data dictionaries, test files, and MATLAB files, all link information related to the artifacts that are on the MATLAB or Project path are automatically loaded when that artifact is loaded.

The link information loading can be summarized by the rules as follows:

Rule 1: Loading an artifact such as requirement sets, Simulink models, data dictionaries, test files, and MATLAB files, that are on the MATLAB or Project path loads all incoming and outgoing link sets for that artifact. Each artifact can have one outgoing link set and one or more link sets containing link information from other artifacts.
Rule 2: If the loaded artifact has outgoing links to a requirement set, then the requirement set is also loaded along with the link information. This loaded requirement set is also eligible to follow Rule 1 to further load link information.

The application of these rules can be illustrated using theslreqCCProjectStartproject in three scenarios. Follow these steps:

Close all the Simulink models and requirement sets before opening the project.
Load theslreqCCProjectStartin the MATLAB:
```
slreqCCProjectStart
```
Scenario 1:
1. Open the modelcrs_controller.slx:
  open_system('crs_controller.slx');
2. OpenRequirements Editor:
  slreq.editor
3. TheRequirements Editorshows following information:
  
  Link information from outgoing link setcrs_controller.slmxis loaded according to Rule 1.
  Requirement setcrs_req_func_spec.slreqxand link setscrs_req.slmx,crs_controllerdic.slmx,DriverSWRequest_Tests.slmx, andcrs_plant.slmxare loaded according to Rule 2.
4. Close the model and theRequirements Editor.
Scenario 2:
1. Open the requirement setcrs_req_func_spec.slreqx:
  slreq.open('crs_req_func_spec.slreqx');
2. TheRequirements Editoropens and shows following information:
  
  Link sets View
  
  All link sets which contain incoming link information for loaded requirement set are loaded according to Rule 1.
3. Close theRequirements Editor.
Scenario 3:
1. Open the modelcrs_plant.slx:
  open_system('crs_plant.slx');
2. OpenRequirements Editor:
  slreq.editor
3. TheRequirements Editorshows following information:
  
  Link information from outgoing link setcrs_plant.slmxis loaded according to Rule 1.
  Requirement setscrs_req_func_spec.slreqxandcrs_req.slreqx和所有链接集包含的链接信息rmation for these requirements are loaded according to Rule 2.
4. Close the model and theRequirements Editor.

Link information is not automatically loaded if you save your links with the model as an embedded link set. You can also load link information by using theslreq.refreshLinkDependenciescommand.

Unload Link Information

Link information is automatically unloaded when you unload all the related artifacts from memory.

Delete a Link Set

Link sets are stored in.slmxfiles. Deleting the.slmxfile while the links are loaded in memory may lead to unexpected behavior.

Note

If you want to delete a link set file associated with a Simulink model, ensure that the links are stored externally. To read more about how to store links externally from a Simulink model, seeRequirements Link Storage.

To delete a link set:

Locate the.slmxfile. By default, when you create a link, it is stored in a link set with the same name as the artifact that the source item belongs to. The.slmxfile is stored in the same directory as the source artifact.
It is best to close all loaded artifacts before deleting a link set. This includes requirement sets,Simulink Testfiles, MATLAB code, Simulink data dictionaries, and Simulink, Stateflow or System Composer models. Manually close all of these artifacts.
At the MATLAB command line, clear loaded links by entering:
```
slreq.clear
```
Delete the.slmxfile.

After deleting the link set file, you can re-open artifacts as needed.