x4GL technology (where x stands for various vendors implementations of I-4GL
product) evolved significantly from the days when I-4GL was the proprietary and
legacy technology, as well as the only implementation of the I-4GL compatible
language available. Significant number of x4GL vendors emerged in last 10 years,
including vendors making compatible products, extending functionality, providing
services including migration and conversion, and even the OpenSource project
with purpose of promoting and enhancing x4GL technology was established.

This document was created to enhance the visibility of all this activity, and
make it easier for a vendor to evaluate its future involvement with x4GL
technology. Primary purpose is to collect in one place sufficient information about various
available x4GL compatible products, vendors and services, for the reader to
learn what is available and what functionality to expect.