What condition must be met for a pin with a lower bound of 0?

A pin with a lower bound of 0 indicates that the pin is not required to have any tokens present at any time; in other words, it is allowed to be empty. This characteristic aligns with the definition of an optional component in a modeling context. Since there is no minimum requirement for the number of tokens, the presence of tokens is optional.

In contrast, a lower bound greater than 0 would signify that at least a specified number of tokens must always be present, making it mandatory. Therefore, for a pin set to a lower bound of 0, the interpretation is clearly that it may or may not contain tokens, thereby reinforcing its optional status in the model.

Understanding this concept is crucial in systems modeling, particularly when assessing the flow of information and the state of components within a system.