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The SmartLdapGroupStore is designed to discover groups of users maintained within an LDAP directory server. It queries an LDAP data source for a collection of group objects and uses their attributes to re-organize them into a hierarchy. As users log in and use the portal, it uses Person Attributes to determine which groups each user belongs to. This behavior is similar to PAGS
Several other implementations of GaP also leverage information from LDAP - PAGS, LDAPGroupStore, JitLDAPGroupStore - and each of these is useful in its own way. The role of SmartLdapGroupStore is to host in the portal groups that are defined and maintained entirely in LDAP. You don't have to state explicitly the groups you want to pull in; SmartLdap will automatically fetch all the groups that match the filter expression.
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