For modeling business processes, there are two standards popular today – UML 2.0 Activity Diagrams and BPMN.
There are semantic differences in notation between the two standards. For e.g. the way OR-splits, AND-splits/joins are shown.
A detailed whitepaper showcasing the differences between the two notations can be found here.
A discussion thread at http://www.bpm-research.com/forum/index.php?showtopic=501 makes an interesting read.