Complex sentence: JScript 5.7 includes an implementation of the ECMAScript Compact Profile (ECMA-327) which turns off features not required by the ES-CP when using the "JScript.Compact" ProgID.
Split into simpler sentences: JScript 5.7 includes an implementation of the ECMAScript Compact Profile (ECMA-327). Which turns off features not required by the ES-CP when using the "JScript.Compact" ProgID.