The SAML2 SP-initiated describes SSO exchange between a Novell Access Manager 3.1 SAML2 Service Provider (SP) and a Shibboleth SAML2 Identity Provider (IDP). Within this exchange, the user attempts to access a resource on the Service Provider.
Since the user has no active session on this Service Provider, the user is asked to login and selects to do so through the Identity Provider server which is references in the SAML trust relationship. As a result, the user is sent to the Identity Provider server to login and the Identity Provider server, once the users credentials are validated, provides a SAML web SSO assertion for the user's federated identity back to the Service Provider..
For more information on Integrating Novell's Access Manager with Shibboleth's Identity Provider Server, refer to http://www.novell.com/communities/node/6943/integrating-novells-access-manager-shibboleths-idp-server#Accessing the Service Provider.