Distributed link service in the Aquarelle project

Abstract

The aim of this paper is to describe briefly the Aquarelle project and the type of distributed link service we are implementing to meet its requirements.KEYWORDS: Link service, Open Hypermedia Systems.1 LINK SERVICE The need for a link service has been indirectly expressed since 1987 by Meyrowitz [1], Brown [2] and Malcolm [3]. Since the first implementation of a link service [4], the concept of separating hypertext facilities from data storage and presentation applications is well established and has been proposed and implemented on local area networks by many [5,6,7,8,9,10,11]. The first design of a distributed link service for wide area networks was presented in [12]. The WWW has further increased the need for such services which now exist in various forms [13,15] and a hypermedia protocol for such services has been proposed [17].In its simplest form, a link server manages links only, i.e. it keeps a simple table of source/destination couples. In its more elaborate form it keeps a representation of the hypermedia objects, i.e nodes, groups, links, anchors, and provides a scripting language as well. The server in this case keeps and manages an entire hypergraph and composites and is said to provide full hypermedia services. THE AQUARELLE PROJECTThe European Aquarelle project aims at providing access services to information describing the European cultural heritage, including paintings, sculptures, historical sites and monuments, musical instruments and furniture. There are two common types of such information: 1) primury &ta which is produced by museums, art galleries, and other cultural organisations that record details of their collections and 2) secondmy duta which is further information which could be specialist knowledge related to the collections. Primary data is stored and managed on what are called archive servers, and secondary data is stored and managed in structured folders, so called because they were originally physical folders maintained by a curator over the years, on folder servers. The information in the folders naturally contains references to items on the archive servers and to other folders on related subjects.Aquarelle is a resource discovery system for cultural heritage information, available in archive (or primary data) and folder (or secondary data) databases on servers Permissionto make di@Ward copies of all or part of this material for personalor classroom use is granted without fee provided that the copies arc uot made nr distributed for profit or commercial advantage, the uJpyright nodce, tbe title of the publication and ita date appear, and notice is given drat copyright is by penrdasion of the ACM, Inc. To copy otherwise, to republish, to post on savers or to redisrnbute to lists, requires specific permissionand/Orfee Hypertext 97, Southampton UK 01997 ACM 0-89791 -866-5,..S3,50Dale Sutcliffe RAL (UK), daiet?inf.rl.ac.uk throughout Europe. It provides information access both through information retrieval by querying and through hypertext navigation. The services offered by Aquarel...

Link services or link agents?

“…This corresponds to the so-called heavyweight client model in which part of the server processing is devolved to the client. Another link service (also known as the Distributed Link Service) has been produced for the Aquarelle project [22]. The advantage of this service is that it is built on top of a robust database managing of millions of links in a way that avoids the dangling links problem.…”