what does SSO authentication touch point used for ?

[zengqingyi12]

I find there are following code in NTLMAuthenticationFilter.java which used for alfresco share SSO authenticate:

               Response remoteRes;
               if (cachedNtlm)
               {
                   Connector conn = connectorService.getConnector(this.endpoint, session);
                   ConnectorContext ctx = new ConnectorContext(null, getConnectionHeaders(conn));
                   remoteRes = conn.call("/touch", ctx, req, null);
               }
               else
               {
                   Connector conn = connectorService.getConnector(this.endpoint, AuthenticationUtil.getUserId(req),
                           session);
                   ConnectorContext ctx = new ConnectorContext();
                   remoteRes = conn.call("/touch", ctx);
               }‍‍‍‍‍‍‍‍‍‍‍‍‍‍

and I found the alfresco/service/touch 's description is:
SSO Authentication touch point, so what is touch point used for ?  And how it works with SSO ?  
Can someone point me the direction or the references ?
Thanks !

[kevinr]

The only way we had a concept of logout with SSO in Explorer was too have a "logout" button that cleared the session and cookies, the message on the logout screen was "press here to login again" which caused the user to reauthenticate via SSO. There's not much else you can do.

Kev