FIXML is the XML encoding used within FIX. FIXML is widely adopted for derivatives post trade clearing and settlement globally. FIXML is also used for reporting.
Client systems can request a snapshot of trades with /TrdCptRepReq/ReqTyp=1 (Matched trades) and /TrdCptRepReq/SubReqTyp=0 (Snapshot) limited by StartTm and optional EndTm attributes.
Client systems can request a snapshot and initiate a continued subscription for trades with/TrdCptRepReq/ReqTyp=1 (Matched trades) and /TrdCptRepReq/SubReqTyp=1 (Snapshot + Updates) with the optional StartTm Attribute.