In addition to the FAQ below, see also the EMF Model Query Developer Guide documentation included in the EMF Query SDK.
Newbie / General
Does EMF Query 1.x work with J2SE 1.4?
Yes and no. The core EMF Query framework works with EMF 2.2 or higher and J2SE 1.4.
However, if you need the OCL extensions in the org.eclipse.emf.query.ocl plug-in, the requirements are different.
See also EMF 2.3 JVM Requirements.