The Validation Plug-In Interface is supported by only the LDAP and Membership authentication module types. An administrator can write username or password validation logic appropriate for a particular realm, and then the plug logic into the Authentication Service. Before authenticating a user or changing the user password, Access Manager will invokes this plug-in. If the validation is successful, authentication continues. If validation fails, an authentication failed page will be thrown. The plug-in extends the com.iplanet.am.sdk.AMUserPasswordValidation class which is part of the Service Configuration SPI.