Capella System Analysis practical example

The steps and diagrams described below you can create them in any order. Steps match the MBSE with Arcadia method step-by-step for System Analysis, and mentioned again below:

Read more: System Analysis

Transition from Operational Analysis

A Capella transition is the mechanism that enables the tool to create model elements and links (aka traceability) at one layer from another.
Model elements transitions are performed to transition model elements from Operational Analysis to System Analysis. When you transition model elements, Capella creates traceability links from System Analysis to Operational Analysis and can be explored using the Activity Explorer modelling tool. In the Activity Explorer (considering it is open) and:

• Under transition from Operational Analysis:
  • Automated transition of Operational Activities.
• Under define Actors, Missions, and Capabilities:
  • Contextually create new System Actor from Operational Entities / Actors.
  • Contextually create new System Capability or Mission from Operational Capability.
• Operational Process transition

Automated transition of Operational Analysis

To perform an automated transition of Operational Activities, click on “Automated transition of Operational Activities”, as below:

The below functional transition window shows three columns:

The below functional transition window shows three columns:

• Synthesis: this column shows the difference between candidate and resulting model.
• Candidate model: it provides the ability to select what model elements will be part of the resulting model.
• Resulting model: shows a preview of the model when performed the transition.

Click on “Copy all to the right” and then “Ok” to perform the transition and close the window.

Contextually create new System Capability or Mission from Operational Capability

Let’s do the automated transition of Operational Capabilities in context with the Operational Actors from the Activity Explorer. From the Activity Explorer click on “Contextually create new System Capability or Mission from Operational Capability”, as below:

Then select “System Capability”, as below:

From the Capability Transition window, you can see realisation and the transformation links from System Analysis to Operational Analysis:

Click on “Copy all to the right” and then “Ok” to perform the transition and close the window.

A final transition for Operational Process

The Play Imposed Video Operational Process describes the Perform Flight On-Board Announcements Operational Capability. We will perform a “Function Transition” to transition the Operational Process.

To transition, select from the Project Explorer, select Play Imposed Video Operational Process at Operational Analysis, then mouse right-click “Transitions” > “Functional Transition”, as below:

The Operational Process functional transition will create involvement links (aka references) to the System Functions referenced by the System Functional Chain. It will also create a realisation link from System Capability to Operational Capability, as below :

Contextually create new System Actor from Operational Entities / Actors

Finally, we will perform a System Actor from Operational Entities / Actors transition. Click on “Contextually create new System Actor from Operational Entities / Actors”, as below:

From the selection dialog, select the Operational Entity and the two Operational Actors (i.e., Passenger and Cabin Crew), as below:

In the Operational Entity to System Actor Transition window, it creates System Actors, System Actor realisation links, but also transformation links (i.e., Operational Entities and Actors to System Actors) and Allocation links, as below:

Click on “Copy all to the right” and then “Ok” to perform the transition and close the window. When completed the System Analysis should look like below:

System Analysis to Operational Analysis realisation links

The realisation links highlighted in sections above, create and allow traceability between model elements captured at System Analysis and Operational Analysis as captured in the figure below:

Realisation links types:

• A: System Actors realise Operational Entities and Actors.
• C: System Capabilities realise Operational Capabilities.
• F: System Functions realise Operational Activities.
• P: Functional Chain realises Operational Process.

Capture Context System Actors

To define a new Context System Actor diagram, select from the Project Explorer and under Structure “System”, then mouse click “New Diagram / Table…” > “Contextual System Actors”, as below:

For this example, the name remains as default: [CSA] System:

Define Missions and System Capabilities

To create a new Missions and System Capabilities diagram, select from Project Explorer “System”, then mouse right-click “New Diagram / Table…” > “Missions Capabilities Blank”, as below:

Let’s start to insert the transitioned Capability in the diagram. From Palette select “Capabilities”, then click on a blank area of the diagram and “Add selected element(s)”, as below:

To insert transitioned System Actor, select from the Palette “Actors”, then click on a blank area of the diagram, then select “Cabin Crew” and “Add selected element(s)”, as below:

To finish this diagram, create the “Provide Cabin Management Solutions Mission” and the Capability exploitation from the Mission to Perform Flight On-Board Announcements Capability, as below:

Define System Functions Breakdown Structure

To create a new System Function Breakdown Structure diagram, select from Project Explorer “Root System Function”, then mouse right click “New Diagram Table…” > “System Function Breakdown”, as below:

You can change the diagram name, but for this example we will keep the same diagram name as default.

We will now refine the Broadcast Movies function allocated to the Aircraft.

To create a new function, select from the Palette “System Function”, then click on the Broadcast Movies function. It creates a new function and containment link. Rename the new function to Play Audio in Cabin, as below:

Repeat the process above and create two new functions contained by Broadcast Movies, as below:

We can change the colour of the Broadcast Movies function to white. This is a proposed practise and visual reference, only, to help to identify transitioned functions and traceability.

Define Functional Exchanges

Next we will create a System Data Flow Blank diagram for the Perform Flight On-Board Announcements Capability. To create a new System Data Flow Blank diagram, select Perform Flight On-Board Announcements Capability, then mouse right-click “New Diagram / Table…” > “System Data Flow Blank”, as below:

You can keep the same default diagram name: [SDFB] Perform Flight On-Board Announcements. When diagram created select from the Palette “Functions”, then click on a blank area of the diagram. The below Transfer Dialog window will open. Select “Add all elements”:

Organise the functions and change the colour of the Broadcast Movies to white, as below:

Move the ports as below:

• From Broadcast Movies (in) to Store Digital Media.
• From Broadcast Movie (out) to Broadcast Audio Video Stream.

Create the Functional Exchange:

• Audio Stream.
• Audio Signal.
• Audio Video Media.

Rearrange the System Functions and ports. The finished System Data Flow Blank diagram, should be similar as below:

Allocate System Functions to System Components and Actors

Let’s create a System Architecture Blank diagram.

First, rename the model element System. Select “System” from Project Explorer and rename to In-flight Entertainment. To create a new System Architecture Blank diagram, select System, then mouse right-click “New Diagram / Table…” > “System Architecture Blank”, as below:

You can keep the same default name: [SAB] In-flight Entertainment.

To insert System Actors into System Architecture Blank diagram, select from the Palette “Actors” then “Add all elements”, as below:

When Actors inserted to the diagram, rearrange, and resize as below:

Let’s insert allocated System Functions to System and Actors. Start by allocating functions to System. Select from Palette “Allocated Functions” then click on In-flight Entertainment System model element. When you see the Transfer Dialog window, select the three functions and click “Add selected element(s)”, as below:

Repeat the process above for Passenger and Cabin Crew Actor. Rearrange and resize the functions as below:

Let’s reallocate system functions. Select Play Audio in Cabin function and drag from In-flight Entertainment to Aircraft, as below:

Aircraft System Actor allocates the Play Audio in Cabin function, hence, the System Data Flow Blank Diagram and System Functional Breakdown Blank diagram updates. You can visualise the function colour changes from green (functions allocated to the System) to blue (functions allocated to Actors):

We will now create the Components Exchanges between all Actors and the In-flight Entertainment. To create new Component Exchange, select from the Palette “Component Exchange”, then click on “Cabin Crew” and then “In-flight Entertainment”, as below:

Functional Exchanges allocate to Component Exchanges. Component Exchanges implement Functional Exchanges.

To create Port Allocation, select from the Palette “Port Allocation”, then click on Component Port owned by Cabin Crew, then click on Function Port owned by Cabin Crew, as below:

Repeat the process above to create the Component Exchanges and Port Allocations, and rename Component Exchanges as below:

Now that Component Exchanges and Port Allocation is complete, there is the need to make sure all Component Exchanges and Port Allocations directions are consistent. Let’s update both ports directions for Imposed Video Playing Status Component Exchange to IN OUT to reflect consistency with Functional Input and Output ports.

To change Component Port direction double click on one Component Port and when the Properties Window opens change the direction to INOUT, as below:

Repeat the process above for the other Component Port. When changed the Component Port directions the System Architecture Blank should be as below:

Use the diagram filters, as figure below to:

• Collapse Component Ports.
• Hide Component Exchanges.
• Hide Port Allocations.

When filters applied the diagram should look like above [SAB] In-flight Entertainment reallocated function figure.

Describe System Capability with Functional Chains

Functional Chains can be created in either System Architecture Blank or System Data Flow Blank diagram in a similar process to the described for the Operational Analysis is section above.

For this example, we will insert the Functional Chain transitioned from Operational Analysis. To insert the Play Imposed Video Function, select from the Palette “Functional Chain” then click on a blank area of the SDFB diagram. When the transfer dialog shows select the Functional Chain and click “Add selected element(s), as below:

Notice that when inserted the Functional Chain next to its name it is shown as invalid. The reason is the Broadcast Movies System Function was broken down and Function Ports delegated. Hence, new leaf functions are added, but not reflected on the Functional Chain.

To correct the Functional Chain there is the need to create a System Functional Chain Description diagram. To create a System Functional Chain Description diagram, select the Play Imposed Video Functional Chain, then mouse right-click “Functional Chain” > “Create a Functional Chain”, as below:

Keep the same default diagram name: [SFCD] Play Imposed Video.

When created the new Play Imposed Video System Functional Chain Description you can see there is a function with no interactions, as below.

The following updates to the System Functional Chain Description:

• Delete from diagram Broadcast Movies. As a reminder this function was initially defined at Operational Analysis, transitioned to System Analysis, and finally refined in two more functions as described in previous section. In addition, the Arcadia rule that only leaf functions should be allocated. In addition, Broadcast Movies is also part of the Operational Process. As the Operational Process was transitioned and Play Imposed Video Functional Chain was created. Hence, Broadcast video belongs to the Functional Chain, but needs to be deleted and only leaf functions should be reference in the Functional Chain
• Insert the new refined functions captured at System Analysis: Play Audio in Cabin.
• Broadcast Audio Video Stream and Store Digital Media are already part of the Functional Chain as the ports were delegated from Broadcast Movies to each function and as described previously.
• Create Exchange between:
  • Broadcast Audio Video Streams and Play Imposed Movie Functional Chain Involvement Function.
  • Play Audio in Cabin to Watch Movie Functional Chain Involvement Function.
• Create Exchange and Function:
  • From Broadcast Audio Video Streams to Play Audio in Cabin.
  • Store Digital Media and Broadcast Audio Video Streams Functional Chain Involvement Function. There is the need to add this new function as Capella prevents closed loops.

When completed the System Functional Chain Description the diagram should be similar to:

Use the Exchange and Exchange and Function from the Palette to add Functional Exchange involvement Functions and links. Functional Chains updated and inserted in System Data Flow Blank and System Architecture Blank diagrams:

Describe System Capability with Functional and Entity Scenarios

Functional and Entity Scenarios describe System Capabilities. You can create Scenarios in a similar way to Operational Scenarios described in Operational Analysis page.

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