An evaluation metric is used to evaluate the effectiveness of information retrieval systems and to justify theoretical and/or pragmatical developments of these systems. It consists of a set of measures that follow a common underlying evaluation methodology. There are many metrics that can be used to evaluate the effectiveness of semi-structured text (XML) retrieval systems. These metrics are based on different evaluation assumptions, incorporate different hypotheses of the expected user behaviour, and implement their own evaluation methodologies to handle the level of overlap among the XML information units.