Tokens
A token is an actant that can be passed on between social or technological actors, for instance in a work systems, or among application components.
In a Petri net, also called place/transition net [1], the distribution of tokens over the places represents a configuration of the net and is called a marking. Processes in the net, including choice, iteration and concurrent execution, proceed via the transition of tokens between places. A transition of a Petri net may fire if it is enabled, i.e. there are sufficient tokens in all of its input places; when the transition fires, it consumes the required input tokens, and creates tokens in its output places. A firing is atomic, i.e. a single non-interruptible step.
In coloured Petri nets [2] the values of tokens are typed, can be tested and manipulated with a functional programming language, as illustrated at the conceptual level in [3].
In the "token in a coloured Petri net" interpretation, the type of the token maps to the kind of information that the actant may contain.
Example of token types are message types of UN/EDIFACT or the common document codes and names, as listed in codelist for element 1001 Document name code (UN/EDIFACT).
When modelling systems in accordance with the ArchiMate architectural framework, tokens could be modeled at the various layers as follows:
| Layer | Tokens |
|---|---|
| business | business object or representation |
| application | data object |
| technology | artifact |
The arrival of a token can be linked to an event, for instance an "order" for a spare part.
