ELM is a machine-readable representation of an eCQM's logic and provides the information needed to automatically retrieve data from an electronic health record. The ELM file can be in XML (.xml) or JavaScript Object Notation (JSON) file (.json).
There are a lot of things that CQL supports. Higher-level constructs, such as timing phrases, are translated into a representation in ELM focused on implementation so you do not have to worry about those pieces within ELM. There is nothing that says you could not do all that yourself. But for implementation, using ELM takes those pieces off an implementer’s plate. Individually each are not terribly difficult, but when you put them all together and add them up, and the fact that we maintain ELM as a part of this whole infrastructure, it is a significant advantage to be able to use the ELM directly rather than have to start from a parser. Refer to the CQL Educational Resources page for additional guidance.