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Constraints define limits on the topic map based on the schema types. There are two basic categories of constraint:
| • | Value constraints limit the values of properties such as names or occurrences based on the Name Type or Occurrence Type |
| • | Combination constraints limits the ways in which types can be combined such as the types of occurrences that can appear on a topic of a particular type, or the types of roles allowed in an association. Combination constraints also specify a minimum and maximum cardinality. The cardinality range allows you to limit exactly how many times the combination is of types are required to or allowed to occur in the topic map. |
The following list describe all of the constraints supported by Web3.
| • | Topic Name Constraint - A combination constraint that limits the type of names that can appear on a topic of a given type. |
| • | Topic Occurrence Constraint - A combination constraint that limits the type of occurrences that can appear on a topic of a given type. |
| • | Topic Role Constraint - A combination constraint that limits the roles that a topic of a given type can play |
| • | Association Role Constraint - A combination constraint that limits the types of roles that can appear in an association of a given type. |
| • | Occurrence Data Type Constraint - A value constraint that restricts the values of an occurrence of a given type to be of a specific datatype. |
| • | Incoming Arcs Constraint - A combination constraint that restricts the types of arcs that topic of a given type may appear at the end of. |
| • | Outgoing Arcs Constraint - A combination constraint that restricts the types of arcs that a topic of a given type may appear at the start of. |
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