Is the Information Flow diagram part of the UML v2.5.1 taxonomy?

Question

According to multiple sources, the Information Flow diagram is not part of the UML v2.5.1 taxonomy.

See examples here:

• https://www.uml-diagrams.org/uml-25-diagrams.html
• https://stackoverflow.com/a/44715082/4216654

According to the UML v2.5.1 (and v2.5.0) specification, it seems that the Information Flow diagram is part of the UML v2.5.1 taxonomy, when in v2.4.1 it was an auxiliary package. Clause 20 of v2.5.1 describes everything about Information Flows. It's still described as a package but it doesn't talk about anything being auxiliary anymore.

It looks like this is something people missed in the transition from v2.4.1 to v2.5.0, but maybe I'm the one who missed something here.

If the Information Flow diagram is indeed part of the UML v2.5.1 taxonomy, it means that many comments, websites, books and software are wrong about it, so I would like to be extra sure about this point. It's likely that I'm wrong about this, so I would be glad to understand why.

I would appreciate any help about this.

Answer 1

In short

Information flows are specified in section 20 of the UML specifications. But apparently, they were not fit enough to survive in the UML diagram taxonomy as own diagram type.

However, you can create a class diagram and populate it only with information items and flows linking source items to target items. This ambiguity leads to contradictory claims: it'll be a real information flow diagram, but in the UML taxonomy it would still be a class diagram (see blue specialisation in your link).

Some more thoughts

What are information flows good for?

According to the UML specs:

The principal goal of InformationFlows is to convey that information moves from one area of a model to another. Consequently, the metamodel is intentionally very permissive about the realization of information channels and the types of information that can flow along them.

So it is to enrich other diagrams to explain how they relate to high level information, or to highlight some hidden «flow» relations (similar to dependencies).

Why didn't the own diagram make it?

In UML, there are better ways to model flows of "information" as soon as you're ready to use classes instead of information items:

• Activity diagrams, which provide object flows,
• Sequence diagrams, which provide flows of messages,
• Communication diagrams, which is semantically equivalent to sequence diagrams, but with a different focus.

Moreover, UML specs explain:

An important use of InformationItems is to represent information during early design stages, possibly before the detailed modeling decisions that will ultimately define them have been made.

But in practice, unless you work in an organisation with extremely strong configuration management rules, there is no need for such information flows in a pragmatic use of UML with initial high-level sketching and iterative refinements.

Answer 2

No, Information Flow Diagrams don't exist in the UML specification. These are the diagram types defined in UML v2.5.1, found on page 685

Information Flows however are part of the UML metamodel and are described in detail in §20 starting page 669.

There is simply no dedicated diagram type defined to show Information Flows. You can show them on other diagrams however such as Class Diagram, Component Diagram, etc..