Abstract
Information overload, arising from di erent types of heterogeneous digital data readily accessible from millions of repositories, is a critical problem on the Global Information Infrastructure (GII). We present an information brokering approach, architecture and techniques that address issues related to information overload on the GII. The approach spans three levels: representation (structure/format/type) of digital data, information content captured in the data; and the vocabulary underlying the data. Metadata (data/information about data) is used to abstract from heterogeneous representational details and capture information content. Domain speci c ontologies are used to represent and interoperate across di erent vocabularies used to characterize information content. The approach thus suggested induces a metadata-based architecture that enables information brokering at the di erent levels. The feasibility of the approach is demonstrated by using a wide variety of metadata to capture information content for textual, image and structured data. These metadata belong to a wide spectrum and may range from metadata independent of the data content to those capturing information content in a application and domain speci c manner. This thesis demonstrates how metadata characterizing information in a domain speci c manner may enable: (a) media-independent correlation of information across ii heterogeneous media; and (b) vocabulary-based interoperation of information across di erent domains. Example information brokering prototypes based on metadata capturing information content to varying degrees are presented as instantiations to validate the proposed architecture. We also identify the desired (SEA") properties of an architecture in the presence of information overload, namely, scalability, extensibility and adaptability; and discuss in what measure the prototypes display these properties. The intrinsic trade-o between scalability and extensibility is identi ed and discussed. Adaptability, a new proposed property, is the ability of an information brokering system to adapt to di erent vocabularies used to describe similar information content. We show how maximizing scalability leads to issues of adaptability and how terminological relationships across domain speci c ontologies characterizing vocabularies may be used to achieve interoperation and increase adaptability.