XML is becoming a standard for representing and exchanging data on the Web. As a result, the quantity of XML documents being processed by web-based information systems has been rapidly increasing. It is generally accepted that there is a need to apply existing database technology for storing and retrieving XML data. However, due to the fact that XML is inherently hierarchical in structure, which is characterized by complex nested tags in an XML document, XML data does not easily fit into the underlying data model of common DBMSs. We propose an XML data model, the Nested Relational Sequence Model (NRSM), which is an extension of the Nested Relational Data Model in order to handle XML data. Within the NRSM, the methods for mapping valid and well-formed XML documents into Nested Relational...[ Read more ]

XML is becoming a standard for representing and exchanging data on the Web. As a result, the quantity of XML documents being processed by web-based information systems has been rapidly increasing. It is generally accepted that there is a need to apply existing database technology for storing and retrieving XML data. However, due to the fact that XML is inherently hierarchical in structure, which is characterized by complex nested tags in an XML document, XML data does not easily fit into the underlying data model of common DBMSs. We propose an XML data model, the Nested Relational Sequence Model (NRSM), which is an extension of the Nested Relational Data Model in order to handle XML data. Within the NRSM, the methods for mapping valid and well-formed XML documents into Nested Relational Sequence relations (NRS relations)are discussed. This thesis demonstrates that the processes of retrieving XML documents and extracting their corresponding DTD from NRS relations are natural and straightforward, since these processes are reversible and information preserving. A set of algebraic operations pertaining to the NRSM, called NRS operations, which allows the manipulation of XML documents through queries imposed on NRS relations is formally defined. We demonstrate the NRS operations and show through examples how XML queries can be formulated in a straightforward manner. Finally, we implemtmt the NRSD System that is built with NRSM as the underlying data model. The NRSD System is a middleware system between users and the relational DBMS, it allows users to manipulate the XML data and perform queries.