STEM help / Model structure

9.2.1 Creating a Collection of elements

Collection elements are created in the usual way:

  • click on the Collection button on the toolbar, or
  • select Create from the Element menu on the Editor main window, or
  • press <Ctrl+Shift+C>.

If there was more than one icon selected previously, each of the corresponding elements will be automatically associated with the new collection element; otherwise the collection will be created with no elements.

Adding elements to a collection

If you have created an empty collection, or you wish to add further elements:

  1. Select the elements you want to add, hold down the <Ctrl> key, click on one of the icons with the left mouse button, and keep the button pressed.
  2. Drag the mouse cursor to one side. A copy of the icons moves off the original.
  3. Move the new icons over the collection icon. Notice that the mouse arrow cursor points down when it is over the collection icon.
  4. Release the mouse button to add the elements to the collection.

You can also drag from the collection to an element – see 4.4.8 Connecting elements.

Alternatively, you right click on the collection and select Details from the pop-up menu. Select Insert Element into List… from the dialog Edit menu and then select the element you want to add to the collection from the Insert Element dialog (or press <Ins> to access the Insert Element dialog directly).

Note: If you want to create a collection of collections, you need to hold down the <Ctrl> and <Shift> keys to effect this action instead of the usual copy and paste metaphor for dragging between elements of the same type.

Removing an element from a collection

In order to break the link between a collection and an element:

  1. Right-click on the link between the icons to display a pop-up menu for the link.
  2. Select Unlink to break the link and remove the element from the collection.

Alternatively, you can right click on the collection and select Details from the pop-up menu. Select the element you want to remove from the Elements box and then select Remove Element from List on the dialog Edit menu (or press <Del>).

How the appearance of a collection icon changes

If you create an empty collection, the icon has the appearance of an empty ring. Watch carefully what happens when you drag, for example, a resource into the collection: a miniature version of the resource icon appears within the ring, to indicate that this is now a collection of resources rather than an empty collection. (To be precise, the icon that appears is a miniature version of the default icon for resources in this view, as selected from the Display Options dialog – see 4.18 Formatting a view.)

Figure 1: Adding a resource to an empty collection

As we shall see, the icon menu for a collection element inherits data items for the elements in the collection. This graphic device gives you a clear indication of what kind of menu you can expect a particular collection to have. If you remove all elements from the collection, the icon reverts to its ‘empty’ state; whilst if you add elements of more than one type, e.g., a resource and a service, the ring shows a miniature plain-dialog icon, showing that this collection has no effective type. (It is not possible to create a tabular dialog for a heterogeneous collection of elements.)

Note: These miniature icons are not shown if you have explicitly chosen an alternative icon for the collection.

Examples of how collections can be used

The simplest application for a collection element is to provide an arbitrary grouping and aggregation mechanism. For example, it may be convenient to group a number of resources representing various local-loop costs from a number of functions.

Figure 2: Grouping resources in the local loop

Alternatively you could develop the market segment example described in 4.11.1 Creating Services for a Market Segment by cross-aggregating the POTS and ISDN Services.

Figure 3: Cross-aggregating POTS and ISDN services

The following section explains how these generic collection elements allow you to access tabular dialogs for the corresponding data – similar to service data for market segments.

 

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