Please consult the following resources as needed. 

CME Cleared Trades (CT) API

FIXML Naming Conventions (PDF)

TREX to FIXML Trade Capture Report Mapping Table (PDF)

TREX to FIXML Trade Type Mapping Table (PDF)

Example of PCS via FIXML (PDF) is an annotated example of a file of PCS (Position Change Specification) data in FIXML format, showing how to create a file and identify the firm and product on each record.
XmlLine.exe utility program takes a text file containing XML as input and outputs a text file in which each XML tag is on a line by itself. Useful for inspecting XML files using NotePad or other simple text editor.

For all FIXML related questions, comments or concerns, e-mail info@cmegroup.com.