Analytics Software

We are working on the strategy to integrate the company portal with OBIEE.
The portal is used for internal and external users (both logs on using Active Directory accounts)

Ideally we'd like to seamlessly integrate OBIEE reports in the portal using SSO so after user logs on once
- to the network/workstation PC (internal)
- to the portal (external)
he doesn't need to pass his credentials again.

We did POC using IIS and the Single Sign On configuration there was easy and working.
However since WebLogic is the strategic Oracle Application Server we'd like to host OBIEE on it, especially to be OBIEE 11g ready.

It seems that OBIEE SSO integration with WebLogic is possible but only with the additional components.
Is that true?
or
Does anyone know how to configure Active Directory SSO there on it's own?
If impossible, what products should we focus on: OSSO (Oracle Single-Sign-On),Oracle Internet Directory (OID),Oracle Access Manager (OAM)?

We're a bit confused as the IIS variant of integration apparently doesn't require any extra software.
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