Muenchian Grouping is an XSLT technique for optimizing the grouping of data in an XSL Transform.
Muenchian Grouping, named after it's founder, Steve Muench, is an XSLT grouping technique which improves the efficiency of traditional XSLT grouping (which typically uses preceding-sibling or following-sibling to determine the uniqueness of the node and hence its eligibility to form a new group).
Instead, Muenchian Grouping uses xsl:key to classify groups, in much the same way as a database index works.