Flowchart diagrams vs. UML activity diagrams

Question

What is the practical difference between using flowchart diagrams and UML activity diagrams? I have some thoughts, but maybe I'm missing an elephant in the room?

Flowchart diagram:

1. Widely used;
2. Easily understood by non-programmers;
3. Old?

UML Activity diagram:

1. Standardized;
2. Supports concurrency;
3. Less known syntax, but still simple enough.

For my case of ad-hoc documenting a particular block of application logic, I decided to go with the flowchart diagrams. More people in the company will be able to understand them.

Answer 1

It might seem as a preference, but if we have a standardized language for describing software systems, Why do we use something else? This can lead to bad habit of overusing flowcharts. Activity diagrams are really simple. But if you decide to describe a more complicated aspect of the system or try to change the part you are describing, you might have to switch anyway. So just use UML and prevent confusion in the future.

Answer 2

As you note, Activity diagrams inherently can include concurrency and timing. If you look at this example cribbed from Wikipedia, shown below, you can observe the section with two heavy horizontal bars, and two parallel activities of "present idea" and "record idea". That is read as "start these activities in parallel, and continue only when both are complete." Flowcharts can't express this within the notation.

Practically, using activity diagrams lets you think clearly about concurrent processes. I think you'll find that anyone who can read a flowchart will quickly adapt.

Activity diagram by ​spanish Wikipedia user Gwaur CC BY-SA 3.0, via Wikimedia Commons: