Because XML has become a new standard for data representation, there is a need for a simple conceptual model that works well with XML-based development. In this research we present a conceptual model for XML, called C-XML, which meets this new need of systems analysts who store their data using XML. We describe our implementation of an automatic conversion from XML Schema to C-XML that preserves information and constraints. With this conversion, we can view an XML Schema instance graphically at a higher level of abstraction. We also describe our implementation of an automatic conversion from C-XML to XML Schema. Our con- version preserves information and constraints as long as we count the special C-XML comments that we insert in an XML-Schema instance to capture the constraints in C-XML that are not representable in XML Schema. In connection with defining C- XML and implementing conversions between C-XML and XML Schema, we are also able to make several insightful observations. We point out ways in which C-XML is more expressive than XML Schema, and we make recommendations for extending XML Schema. We also point out ways in which XML Schema is more expressive than conceptual models, and we make recommendations for augmenting traditional con- ceptual models to better accommodate XML. The work accomplished in connection with this research establishes the basis for several fundamental activities in system analysis, design, development, and evolution.