Elements Process Knowledge is powerful due to its simplicity. Process models constructed with the simple set of objects are more easily understood and engaged with by the broadest possible audience. The learning curve is shorter than with diagrams with flowcharting shapes or the palette of BPMN symbols and the associated rules.
An analogy would be that process knowledge is plain language, whereas flowcharting is a process professional’s way of turning plain language into a diagram where you have to understand a set of symbols, both to draw the diagrams and interpret them.
BPMN is essentially a structured graphical programming language, understood by far fewer people. All are powerful. What are you trying to achieve?
So, dealing with each in turn below:
Flowcharting ‘primary example’ from Wikipedia section on Business Process Mapping.
We are showing this as a random, typical example of a flowchart. Scroll down to see where we have turned the information on the flowchart into a process map in Elements, showing the simpler format in Elements and the knowledge missing from the flowchart.
Note : There are ‘decision box’ diamonds in the flowchart. There are none in the Elements process knowledge diagram. Look carefully at the flowchart. The diamonds represent a flow (a Y/N answer to a binary question) – not a decision. As such, they are replaced by the two flows in the Elements diagram. Even if you are trying to represent a decision, how often is it really a binary (Y/N) decision? In real life you have to “decide what do when X happens” – which might have three, four, or "n" number of outcomes. So, describe the decision and show the "n" flow lines that might result. We have 20+ years of experience of showing that you really don’t need decision boxes to explain how things work. Take a good look (or see this short video example).
So, taking the information in this (Wikipedia) flowchart example and mapping it in Elements:
The Elements Process knowledge diagram below has been created only by using the above flowchart – applying the simple notation “Who needs to do What, When, Why and How?”. It is interesting to note that in taking the information from the flowchart to put into Elements, there are many times when it is not clear from the above flowchart information who does these activities, or when, or why. The two red lines are what we guess is going on (based on common sense) – but is not explicit in the flowchart.
This notation is called "Universal Process Notation" (UPN). It's an open standard - you can see more on UPN here.
So what about BPMN 2.0?
BPMN is an industry standard Business Process Mapping Notation - from OMG.org, to repeat the above analogy: process knowledge is plain language whereas BPMN is essentially a structured graphical programming language, understood by far fewer people.
Another way to make the difference clear would be to have a look at the half page specification for mapping in Elements process knowledge (or the simple process map above), and then take a look at the 508 page (current) Specification of BPMN 2.0.
So, for example, this is a "simple" email voting process using a fraction of the many symbols, graphical variants and rules, taken from the Wikipedia entry for BPMN.