You wear Cisco Emplyee badge. You should provide answers related to products rather than ask ...
Well. It's not so clear what's you are askin' about.
SPA50x class of phones can integrate with LDAP server to provide directory informations. But SPA501 have no display, so there's no way to display those information.
Se even if SPA501 will integrate with a LDAP server, you will have no benefit from it.