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Both original Sirtfi (v1) and Sirtfi v2 will remain supported for the indefinite future. There is no plan to deprecate v1 with the introduction of v2. See Coexistence of Sirtfi v1 and v2 for details. Best practice is to encourage adoption of Sirtfi v2 by your members but to support those members who wish to remain at v1. For reference: Sirtfi v1 specification and Sirtfi v2 specification
Sample Outreach Letter for Federation Participants
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