A Constraint controls the input value of a property. Constraints can be used to validate the input values and to ensure certain predefined values for the properties. Constraints are defined separately from content types and aspects and referenced within a property type definition.
Alfresco provides four types of constraints out-of-the-box as follows. Apart from these, the custom constraints can be defined using Java Programming language.
REGEX: ensures that a property value matches a regular expression pattern
LIST: ensures that a property value is picked up from the list of predefined values
MINMAX: ensures that the given property value falls within a defined numeric range
LENGTH: ensures that the given property value falls within a defined character length range