Design Non-recursive and Redundant-Free XML Conceptual Schema with Hypergraph

Data Type Definition(DTD) and XML Schema Definition(XSD) arethe logical schema of an XML model, but there is no standard format for theconceptual schema of an XML model. Conceptual modeling is a very importantfirst step for constructing a database application. A conceptual model describesa system that is being built. Abstract ideas are made concrete as the ideas arerepresented in a formal notation. A formal conceptual model has a number ofadvantages. First, it helps designers understand and document the applicationunder construction. Second, it facilitates development of algorithms that derivethe underlying database schemas. In this paper, a real world of interest isdescribed in a conceptual-model Hypergraph, which is a generic conceptualmodel. It is a Hypergraph because its hyperedges, or simply edges, are notnecessarily binary. Its vertices represent sets of objects and its edges representrelationships among the vertices. Edges in a Hypergraph can be directed orundirected, depending on whether the underlying relationships are functional ornon-functional. As opposed to relational databases, in this paper we areinterested in constructing XML database applications with “good” properties.Two properties are particularly outstanding. First, the database should not haveredundant data because redundant data lead to multiple-update problem once asingle copy is modified. Second, since joins are expensive, the number ofgenerated scheme trees, which are a generic hierarchical storage structure,should be as few as possible in order to reduce the number of joins required toanswer a query. Users can draw a Hypergraph as XML conceptual schema withdata relationships among elements as a result of specified functionaldependency and multivalued dependency.