This document defines the Multidimensional Quality Metrics (MQM) framework. It contains a description of the issue types, scoring mechanism, and markup, as well as informative mappings to various quality systems. MQM provides a flexible framework for defining custom metrics for the assessment of translation quality. These metrics may be considered to be within the same “family” as they draw on a common inventory of values for data categories and a common structure.
Also check this page: http://www.qt21.eu/mqm-definition/issues-list-2015-12-30.html
http://www.qt21.eu/