Requirements verification

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Systems Modeling Language (SysML) captures systems design as descriptive and analytical system models, which relate text requirements to the design and provide a baseline for analysis and verification. With the system parameter calculated, you can verify the system requirement and decide whether it is satisfied. The modeling tool enables you to perform this verification automatically.

Getting ready for automated Requirements verification

Before performing the automatic Requirements verification, you need to get ready.

To get ready for automated Requirements verification

1. Define the constraint in the Requirement text.

2. Create a Satisfy relationship from the Value Property to the Requirement.
   

   The Value Property captures the system parameter whose value determines whether the system requirement is satisfied.

3. Do one of the following:

• • If the Underline Patterns in Requirement Text option is enabled, the condition pattern in the Requirement text is underlined. Move the mouse pointer over it to see the expression in the tooltip. If correct, you are ready to perform the automatic Requirement verification.
    
    

    Learn more:
      - How enable/disable the Underline Patterns in Requirement Text option.
      - How to define custom condition patterns.
      - How to check predefined condition patterns.
      - How to extract the Constraint from Requirement text.
    

• • If the  expression in the tooltip  is not correct,  do the following:

1. 1. Perform either of the two options:
      • Right-click a value property in the compartment area of the element shape.
      • Right-click the Requirement.
   2. Select Tools > Extract Constraint Block From Requirement to create a Constraint Block automatically.
   3. You can modify the constraint expression and the parameters as needed (see Figure A below).

You are now ready to perform the automatic Requirement verification.

In the example above, a Constraint Block with the constraint {totalMass <= 20} and the constraint parameters is automatically created. The constraint expression is then modified to {tm=clm+html+ctm+snm+m}{tm<=20}.

Performing automated Requirements verification in Requirement Table 

The automated Requirements verification analysis can be done directly in the Requirement Table. The analysis evaluates whether the property's value that satisfies the Requirement falls within a range of upper and lower bounds extracted from the Requirement text. Additionally, the automatically calculated margin value helps to determine how close the system model is to fulfilling Requirements.  

To perform automated Requirements verification

1. Create a Requirement Table. You can also use an existing Requirement Table. 
2. Specify the scope for the table.

3. Set the context element (i.e., a Block as the table context) to perform the context-specific analysis. 

   The Requirement Table with the Property, Bounds, Value, and Margin columns is created, and passing/failing Requirements are marked (see an image below). 

Using the Requirement patterns mechanism, the constraint extracted from the Requirement text is shown in the Bounds column. The Value column shows the initial value  (if it exists) or the default value of the Value Property. Finally, the Margin column displays the difference between the calculated and required values.

Performing automated Requirements verification in Instance Table

You can also carry out Requirements verification analysis in an Instance table. While the verification in a Requirement table allows you to perform the analysis for a single instance set as the context, the verification in an Instance table allows you to perform the analysis for multiple instances simultaneously via the Enable Patterns-Based Verification option. In an Instance table, the columns represent the properties provided by the classifier specified for the table, and the appropriate cells display the property values specified in the instances you choose to display in the table.

To perform automated Requirements verification in Instance Table

1. Create an Instance Table.
2. Specify the classifier for the table (i.e., the Block containing the properties satisfying the requirements).
3. Set the scope for the table or add individual instances to the table. 
4. Select the properties to be displayed in table columns.
5. In the table toolbar, click the Options button and select Enable Patterns-Based Verification to enable the verification.
   The Instance table displays the selected instances and performs the verification, which is visible via the highlighted cells based on their verification status (definition is specified in the Legend).
   

Performing automated Requirements verification using simulation

With the help of simulation, you can perform automatic Requirements verification.

To perform automatic Requirements verification using simulation

1. Right-click the Block, which contains the Value Property.
2. From the shortcut menu, select Simulation > Run.

3. In the Question dialog, click  Yes to load the validation rules and validate the model before the simulation or  No to simulate the model without validating it.
   

4. In the Simulation window, click or press F8 to start the simulation.
   The result indicating whether or not the value is satisfied is shown in the Variables pane. In the following figure, you can see when the Requirement is not satisfied (highlighted in red) and satisfied (highlighted in green). You can change the value directly in the Value cell, and the Requirement constraint is checked automatically.
   
   
   

Reviewing Exported Runtime Values in Tables

When you perform Requirements verification using simulation, you can export the simulated runtime values to Instance Specifications. The verification data (the constraint, requirement, timestamp, margin, and status) is stored within tagged values of the «VerificationStatus» stereotype, which is applied to the slot values of the exported Instance Specifications.

The table below lists the tagged values of the «VerificationStatus» stereotype.

Once the instances are enriched with verification-specific data (exported runtime values), you can use them in either Instance or Requirement tables to review the verification results. But before that, you need to ensure that the Enable Patterns-Based Verification option is turned off. 

To learn more, see the Enable Patterns-Based Verification option page.

Webinar: Automated Requirements Verification