Attribute syntaxes are essentially data type definitions. The syntax for an attribute type indicates the type of data meant to be held by the corresponding values. This can be used to determine whether a particular value is acceptable for a given attribute, as well as to provide information about how the directory server should interact with existing values.
Sun Java System Directory Server 5 releases do not support the ability to reject values that violates the constraints of the associated attribute syntax. This capability has been added in Sun Java System Directory Server Version 6, although it is off by default for compatibility reasons (in order to support existing deployments where there are attribute values that violate the associated syntax). The directory server also supports the ability to reject values that violate the associated attribute syntax, and this is the default behavior for the purposes of standards compliance. For compatibility reasons, it is possible to completely disable this attribute syntax checking if necessary, but it is also possible to accept values that violate the associated syntax but log a warning message to the directory server's error log every time this occurs. Note, however, that because the directory server is much more standards compliant in its use of schema elements than the Sun Java System directory server, if attributes are allowed to have values that violate their associated syntax, then matching operations might not behave as expected with such values.