Muenchian grouping

Muenchian grouping (or Muenchian method, named after Steve Muench) is an algorithm for grouping of data used in XSL Transformations v1 that identifies keys in the results and then queries all nodes with that key. This improves the traditional alternative for grouping, whereby each node is checked against previous (or following) nodes to determine if the key is unique (if it is, this would indicate a new group). In both cases the key can take the form of an attribute, element, or computed value.