tailieunhanh - A Visual Retrieval Environment for Hypermedia Information Systems

Addressing the options for domestic sustainable agriculture policies in developing countries, it is generally observed that the world’s agriculture trade system is progressively moving towards an open-market system, a process which is desirable from both a trade as well as a sustainable development point of view. Transforming domestic support regimes towards decoupled and only minimally trade distorting support schemes will have mostly positive effects as it limits distortions, but still provides countries with flexibilities to pursue legitimate agri-environmental and rural development objectives. Nevertheless, while liberalizing national farming sectors it is further imperative that appropriate mechanisms are set up that provide competitively disadvantaged farmers with income and secure food. | A Visual Retrieval Environment for Hypermedia Information Systems DARIO LUCARELLA and ANTONELLA ZANZI Centro Ricerca di Automatica ENEL We present a graph-based object model that may be used as a uniform framework for direct manipulation of multimedia information. After an introduction motivating the need for abstraction and structuring mechanisms in hypermedia systems we introduce the data model and the notion of perspective a form of data abstraction that acts as a user interface to the system providing control over the visibility of the objects and their properties. A perspective is defined to include an intension and an extension. The intension is defined in terms of a pattern a subgraph of the schema graph and the extension is the set of pattern-matching instances. Perspectives as well as database schema and instances are graph structures that can be manipulated in various ways. The resulting uniform approach is well suited to a visual interface. A visual interface for complex information systems provides high semantic power thus exploiting the semantic expressibility of the underlying data model while maintaining ease of interaction with the system. In this way we reach the goal of decreasing cognitive load on the user with the additional advantage of always maintaining the same interaction style. We present a visual retrieval environment that effectively combines filtering browsing and navigation to provide an integrated view of the retrieval problem. Design and implementation issues are outlined for MORE Multimedia Object Retrieval Environment a prototype system relying on the proposed model. The focus is on the main user interface functionalities and actual interaction sessions are presented including schema creation information loading and information retrieval. Categories and Subject Descriptors Database Management Logical Design data models Information storage and Retrieval Information Search and Retrieval query formulation selection process