Allows the cardinality of a given entity to be changed.
The options provided show only the commonly used values, if you have more specific requirements, then you will have to set them in the properties window.

0..1

The entity can appear in the XML document 0 or 1 times, it is in effect optional.

0..unbounded

The entity can appear in the XML document 0 or more times, it is in effect an unbounded collection.

1..1

The entity must appear in the XML document once, it is in effect mandatory.

1..unbounded

The entity can appear in the XML document 1 or more times, it is in effect an unbounded collection, which can not be empty.