The main theorem of the paper states that the empty marking ∅ is reproducible in a p/t-net N if and only if there are reproducing T-invariants whose net representations have neither traps nor co-traps (deadlocks). This result is to be seen in connection to modeling processes, since all processes which have a start and a goal event usually reproduce the empty marking.

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Free worded exercise solutions involve the advantage that students entirely have to resort to their own knowledge. However, their disadvantage is that they cannot be corrected automatically – in contrast to exercises with preset solution possibilities, e.g. multiple choices. This paper outlines these two types of exercise solutions, the methods and some results of a pragmalinguistic analysis of...

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