Per the UML 2.5.1 specification:

DeployedTargets are shown as a perspective view of cube labeled with the name of the DeployedTarget shown prepended by a colon. System elements deployed on a DeployedTarget, and Deployments that connect them, may be drawn inside the perspective cube. Alternately, deployed system elements can be shown as a textual list of element names.

Two example figures from the UML 2.5.1 specification:

Example UML Specification 2017

I figured that without the colon or underline, the Deployment is an instance, but how should we differentiate between them? For example, in a Google Chrome box, should the deployment diagram be underlined?

  • link to the thing you are taking the diagrams from?
    – Ewan
    Commented Mar 26 at 16:52
  • @Ewan I checked - it's the UML specification. See my edits. They appear in the 2.5.1 version, which is the current version. I didn't check older versions.
    – Thomas Owens
    Commented Mar 26 at 16:58

2 Answers 2


Jeeze they make this complicated.

I think the first example (19.14) is underlined because it's an "InstanceSpecification" of an AppServer.

An InstanceSpecification is depicted using similar notation to its classifiers, but in place of the Classifier name appears an underlined concatenation of the instance name (if any), a colon (‘:’) and the Classifier name or names

The Second (19.15) is just a diagram of the communication, which doesn't relate to a specific instance. So its not underlined.

I'm not sure this makes a whole load of sense, if we look at fig 19.3 for example. Here we have a "Deployment" or "DeploymentTarget"? which seems to show an almost identical thing, but with an underline and colon.

fig 19.3

I think the intended use of the underline is to represent a specific instance of a thing rather than the specification of a thing. If we look at the class and other examples we have :Person and D̲o̲n̲ ̲:̲ ̲P̲e̲r̲s̲o̲n̲

When it comes to InstanceSpecifications, it seems odd that they are underlined as they can represent non-existing instances. so I would expect diagrams to have :AppServer or a̲p̲p̲S̲e̲r̲v̲e̲r̲1̲:̲A̲p̲p̲S̲e̲r̲v̲e̲r̲. But there seems to be confusion in the specification as to whether InstanceSpecifications are specifications, or instances


According to a tutorial on sparxsystems.com, the name of a Node is not underlined, whereas the name of a Node Instance is underlined.

Also, "The Unified Modeling Language User Guide" from 1999 mentions that "Nodes are also class-like in that you can specify attributes and operations for them." (p. 363). In the first example of a deployment diagram where they used underlined names they mention that "This diagram is a bit different from the previous one in that it is an object diagram, visualizing specific instances of each node." (p. 366).

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