XML Schema Definition (XSD) is the logical schemas of an XML model, but there is no standard format for the conceptual schema of an XML model. Therefore, we propose an XML Tree Model (XTM) as an XML conceptual schema for representing data semantics in a diagram, and also as an XML data model validator for confirming the data semantics required by users. An XTM consists of hierarchical nodes representing all the elements, and the data relationships among elements within the XSD. A rule-based algorithm and an information capacity with preand post-conditions are developed as the methodology for reverse engineering. The proposed algorithm consists of two rules: General Information Transformation and Data Semantic Recovering to construct an XTM.. Users can draw an XTM with data relationships among elements as a result of the reverse engineering.