Grant: Discovery Development Grant

The nature of data on the web and the flexibility of XML have resulted in data encoded in XML to be semistructured. The availability of large amounts of heterogeneous distributed data necessitates integrating XML data from multiple XML sources. The XML data sources may be based either or no schema, DTD (Document Type Definition) schemas, XML Schema, or any other schema that has been proposed by different companies. Due to the nature of data available on the web that may include patient data in a healthcare system, employee data in a banking industry or any big organization or student data in a university system, all require securing the data. This further necessitates that authorized users with access rights and privileges are able to access the required data in in order to accomplish their jobs efficiently. In order to provide secure access of XML data to authorized users with given access privileges requires the development of a fine grained access control mechanism to provide access to either parts of a document tree or certain nodes in the tree. To enforce such access control models requires availability of XML Schema that specifies the structure of accessible XML data as the schemas provide the mechanism for data exchange, integration, query formulation and optimization. The objective of this research is to develop mechanisms to define security specifications using XML Schema and to effective enforce such constraints during query processing. Enforcing of these constraints will be based on security views. Security views represent a restricted view of the original document and the accompanying XML Schema that can be derived based on a security specification. Further, a security view would expose only the required schema structure and document content to authorized users with access privileges. Authorized users will be able to pose queries over the security view of the XML Schema to formulate their queries.