In this paper we briefly describe a new conceptual model for XML called XSEM. It is a combination of several approaches in the area. It divides the conceptual modeling process to conceptual and structural level. At the conceptual level, we design an overall conceptual schema of a domain independently on the required hierarchical representations of the data in XML documents. At the structural level, we design required hierarchical representations of the modeled data in different types of XML documents. In this paper, we further extend XSEM for modeling IS-A hierarchies. We also show how conceptual XSEM schemes can be represented at the logical level in XML schemes specified in the XML Schema language.