Section 10.3.7, Device (from Nodes), in the UML 2.2 specification contains the following deployment diagram (see page 206).
Figure 1 – Notation for a Device
Clearly, all the nodes in this diagram are instances. With this in mind, let’s try and recreate a similar diagram using Rational Software Architect 7.5.
Creating the AppServer and J2EEServer elements is pretty straightforward. A graphical representation of the model looks something like the following. In the example below I’ve added some attributes to the AppServer device to highlight the fact it’s an element specification, not an instance.
Figure 2 – Deployment Model
If you selected the "Blank Deployment Package" template and default model capabilities in the model creation wizard, the ability to add node instances will be disabled. To remedy this you need to select the capabilities tab in the model properties panel and select the "UML Specific Instance Type 1" and "UML Specific Instance Type 2" options.
Figure 3 – Enabling Node Instances
Once this is done you can starting adding node instances to your deployment diagram. For example.
Figure 4 – Deployment Diagram
The problems arise when you try and add nested nodes to the diagram because, basically, you can’t. As the following figure shows, the properties panel appearance tab options for showing textual and/or graphical nested node compartments are absent for node instances.
Figure 5 – Node Instance Properties
Unfortunately, the help documentation is totally unhelpful as it contains the following section
Nesting nodes inside other nodes
In UML modelling, you can nest nodes within nodes to represent the hardware and software components in a system that contains other components.
A diagram must be open in the diagram editor, and the diagram must contain at least two nodes. The Nested Nodes compartment of the container node must be visible.
To nest a node in another node, in the diagram editor, click one node and drag it into the Nested Node compartment of another node.
As the following figure illustrates, a node named Node2 is displayed in the Nested Nodes Textual and Nested Nodes Graphical compartments of another node, named Node1.
Figure 6 – Rational Software Architect Help
What they fail to mention is that none of this applies to node instances. I raised this with Rational Support and after a month’s deliberation they finally confirmed that nested node instances are not currently supported.