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January 2012 [Cradle 6.5.1]

How to Create a Matrix for Three Sets of Items

In the demonstration database DEMO supplied with all Cradle systems, a set of user requirements are linked to a collection of system requirements and some of these system requirements are linked to a system breakdown structure (SBS). These items and cross references can be shown in a tree:

The cross references can also be shown in a matrix by displaying the user requirements as rows, the SBS items as columns and the system requirements that connect them together as the matrix cells.

Login to the demonstration project DEMO as the user REQMAN, password REQMAN and in the Working Area on the right side of the UI, right click and choose New Matrix… from the pop-up menu:

This will display the Matrix Details dialog:

in which matrices can be defined and modified. You can also open the Matrix Details dialog from the Windows pull-down menu in the Menu Bar, by pressing CTRL-F12 and by selecting the:

button from the controls in the top-right corner of the WorkBench UI:

To create the matrix, you must specify:

  • One or more queries for the columns, each with a view to control how the items found by the queries will be shown in the column headers
  • One or more queries for the rows, each with a view to control how the items found by the queries will be shown in the rows headers
  • That the cells are to contain linked items, and the view to be used to show the items
  • The cross references between the row items and the items in the cells
  • The cross references between the items in the cells and the items in the columns

The Axes tab is selected by default and the Show: drop-down list defaults to Column Queries. Select Add to choose a query to be shown in the matrix columns, select the Query: drop-down list and set this to be the Automatic scope query SBS – All:

Select the Title view: drop-down list and choose the Automatic scope view SBS – Xrefd which simply displays the items’ identities and names. This completes the definition of the matrix columns:

Select the Show: drop-down list and choose Row Queries and select the Automatic scope query Req – All and the Automatic scope view Req – Xrefd. This completes the definition of the matrix rows:

To complete the matrix definition, select the Contents tab to specify what will be shown in the matrix cells:

Select Linked Items from the Contents: drop-down list as we want the cells to show the system requirements that connect the user requirements and SBS items:

From the Type: drop-down list select SYSTEM REQ so that only system requirements will appear in the matrix cells and only cross references between SYSTEM REQ items and the user requirements and SBS items will be used to produce the matrix:

Hence the selection of a specific item type for the matrix cells implicitly performs a filtering of the cross references that are used to produce the matrix.

You can also allow all types of intermediate items to be shown in the cells of the matrix. If you do this, then you will need to specify a generic view for these items in the View: drop-down list.

From the View: drop-down list select the Automatic scope view SYSTEM REQ – Xrefd which will simply show the identity and name of the SYSTEM REQ items that connect the user requirements and SBS items:

Finally, you need to specify the navigations that will be used to select the cross references from the user requirements in the rows to the system requirements in the cells, and from the system requirements in the cells to the SBS items in the columns.

You can choose a navigation that will filter these sets of cross references based on their link type, direction or any of the user-defined attributes that may be stored in the cross references. You can also choose a navigation that will find transitively cross referenced items by following chains of multiple cross references between multiple items that connect the user requirements and the system requirements, or by following chains of multiple cross references between the system requirements and the SBS items.

That is, your choice of navigations not only controls how cross references will be filtered to create the matrix, but also controls whether the matrix will show:

  • Items in cells that are directly or transitively (indirectly) linked to items in the rows found by the query
  • Items in cells that are directly or transitively (indirectly) linked to items in the columns found by the query

When defining the navigations, it may be helpful to think of the default direction used in the matrix:

  • From the rows to the cells
  • From the columns to the cells

And so therefore:

  • From the rows to the cells is downwards
  • From the cells to the columns is upwards

You will set the navigation to be used between the rows and the cells in the Row navigation: drop-down list, and the the navigation to be used from the cells to the columns in the Col navigation: drop-down list.

The navigations that would normally be used are the System scope navigation Downwards and the System scope navigation Upwards. If you are not sure which is the correct direction to use for your matrix, use the System scope navigation Bidirectional in both places, since this navigation does not filter cross references at all.

For this matrix, set Row navigation: to the System scope navigation Downwards and Col navigation: to the System scope navigation Upwards:

This completes the definition of the matrix. Select New to display the matrix in a new tab in the current pane in the WorkBench UI. There are very few cross references between the first few user requirements and SBS items, so the first few rows and columns are empty. If you scroll the matrix, you will see the cross references that do exist between the user and system requirements and the SBS items.

In particular, if you scroll so that user requirement 1.7 and SBS item 1.3.1 are visible, you can see the relationship between Requirement item 1.7, SYSTEM REQ item 2.2.1 and SBS item 1.3.1 that was shown in the tree view at the start of this section:

To show column headings for the display of the system requirements, select the Show column headings checkbox in the Contents tab:

Select Apply to update the matrix in the same display pane:

If you want to save this matrix definition, select Save As:

then enter a name and scope for the new matrix definition and select OK.

You can remove all of the blank rows and columns from the matrix by choosing different queries for the rows and columns. If the query used for the rows only finds user requirements that are linked to a system requirement:

and if the query used for the columns only finds SBS items that are linked to a system requirement:

and the matrix is changed to use these new queries:

then the matrix will be more compact:

This matrix does not display a user requirement if it is not linked to any system requirements, and it does not display a SBS item if it is not linked to any system requirements. So, the matrix can never have any empty rows and it can never have any empty columns. By not showing unlinked user requirements and unlinked SBS items, you may believe that the matrix does not show valuable information; which items are unlinked. This is why the first matrix was configured to show all user requirements and all system requirements.

A compromise between these alternatives would be for the rows to contain bottom-level user requirements and for the columns to contain all SBS items. The rationale for such a matrix would be that it is only the bottom-level user requirements that would be linked to system requirements. Such a matrix could have empty rows and columns. If this rationale is consistent with the process used in your projects, then this approach is recommended by 3SL.

You can reference these matrix definitions in reports and the phase hierarchy. You can generate them from the c_table command line utility. You can also generate them in documents produced by the Document Publisher tool.