Hi:
It sounds to me like you can use attached data from a routing strategy to attach what we call in Genesys Key-Value pairs.
For instance, when you used converse vector you could pass up to two items - for example ANI and DNIS - inband using DTMF. In SIP, the ANI and DNIS are already with the call when it arrives in the SIP messaging, but any additional information which may have been attached by an agent or a routing strategy would also be available in the Composer application if it was previously attached.
I hope this answers your questions.
Thanks,
Kevin