210 likes | 228 Views
This lecture discusses the issues in hypertext systems and how they are addressed in the World Wide Web (WWW) and the Semantic Web. Topics covered include search and query, composites, virtual structures, computation, versioning, support for collaborative work, and extensibility. The lecture explores the implementation of the WWW and its relevance as a hypertext system. The concept of the Semantic Web as the next generation web is also introduced.
E N D
CSA3080:Adaptive Hypertext Systems I Lecture 8:Hypertext Issues and the WWW Dr. Christopher Staff Department of Computer Science & AI University of Malta 1 of 21 cstaff@cs.um.edu.mt
Aims and Objectives • DHRM has very few implementation examples • The WWW, while not DHRM-conformant, is the single largest and most popular example of a distributed hypertext system • There are general hypertext issues, which DHRM attempted to address • The implementation of the WWW has led to other issues, which AHS attempt to address 2 of 21 cstaff@cs.um.edu.mt
Issues in Hypertext • Halasz (again :-)) wrote “Reflections…” in 1987 • It re-surfaces frequently at conferences on Hypertext • Provoking much discussion and updating • Halasz believed that “hypertext” would “disappear”, becoming an underlying mechanism for storing and linking information • Hypertext is still very much “in our face”… 3 of 21 cstaff@cs.um.edu.mt
Issues in Hypertext • “Seven Issues” References: • Reflections on NoteCards: seven issues for the next generation of hypermedia systems Frank,G. Halasz July 1988 Communications of the ACM, Volume 31, Issue 7 • ACM Journal of Computer Documentation (JCD), Volume 25, Issue 3 (http://portal.acm.org/toc.cfm?id=507317&type=issue&coll=ACM&dl=ACM&CFID=14254782&CFTOKEN=22435962). Entire issue devoted to “Seven Issues” • Seven Issues, Revisited. Panel Session, Hypertext ‘02. 4 of 21 cstaff@cs.um.edu.mt
The Seven Issues • Search and Query • Composites • Virtual Structures and dynamic information • Computation • Versioning • Support for collaborative work • Extensibility and Tailorability 5 of 21 cstaff@cs.um.edu.mt
Issues in Hypertext • Search and Query • as part of the hypertext model! • Current generation web has 3rd party search engines • Semantic Web *may* be able to refer to objects via their content, rather than URL (or at least, do it seamlessly!) 6 of 21 cstaff@cs.um.edu.mt
Issues in Hypertext • Composites • Web still doesn’t really support composites, though it can be achieved through dynamic HTML • But watch out for the Dark Web! 7 of 21 cstaff@cs.um.edu.mt
Issues in Hypertext • Virtual structures and dynamic information • So that the network can reconfigure itself according to the information it contains • Self-repairing links, links which bind to the best destination when it becomes available • Web approximates by redirecting to relocated information… 8 of 21 cstaff@cs.um.edu.mt
Issues in Hypertext • Computation • The end of a link can be a computation • The computation can decide what destination to visit, etc. • Web can do… e.g.., search engines! 9 of 21 cstaff@cs.um.edu.mt
Issues in Hypertext • Versioning • Shudder!!!! • Some systems/editors provide versioning (e.g., SCCS for source code development) • Web absolutely does not! 10 of 21 cstaff@cs.um.edu.mt
Issues in Hypertext • Support for collaborative work • Web/internet is a collaborative place. We are sometimes aware of other people in this space • Yet collaboration on, say, development of a web site is not possible within the Web (i.e., there is no explicit support for it). • Web site updating is merely replace currently live page in Document directory • No locking, etc., of files supported 11 of 21 cstaff@cs.um.edu.mt
Issues in Hypertext • Extensibility and tailorability • The “programmable” Web • Servers can be independently configured/extended • Plug-ins increase support for doc types • Web browsers can be configured for individual user, etc 12 of 21 cstaff@cs.um.edu.mt
WWW • The WWW is the single largest example of a distributed hypertext system • But is it a good example of a hypertext system? • And does it really matter if it’s a good example? 13 of 21 cstaff@cs.um.edu.mt
WWW • The WWW was not developed with a formal model in mind • Based on the concept of a Uniform Document Identifier, HTTP, and a standard markup language (HTML) • TCP/IP used as the transport protocol • Link source is marked by <A HREF> tag, with an embedded destination • Reference: • Berners-Lee, T., et. al., 1994, “The World-Wide Web” in Communications of the ACM, Vol. 37, No. 8. August 1994. 14 of 21 cstaff@cs.um.edu.mt
WWW • Simple model, yet powerful • Can share documents across the globe • Anyone can author a Web page • With extensions to original model, can create pages dynamically • Can manipulate multimedia data • HTML still presentation markup language 15 of 21 cstaff@cs.um.edu.mt
WWW and DHRM 16 of 21 cstaff@cs.um.edu.mt
WWW and DHRM 17 of 21 cstaff@cs.um.edu.mt
Semantic Web • Next generation web attempts to overcome some of these problems • Thing is, “fixes” are built on top of existing structure, rather than bottom-up re-modelling 18 of 21 cstaff@cs.um.edu.mt
Semantic Web 19 of 21 cstaff@cs.um.edu.mt
Semantic Web 20 of 21 cstaff@cs.um.edu.mt
So… does it matter? • The (Semantic) Web will address some of the concerns in Seven Issues (but don’t forget about the other issues addressed by AHS!) • SemWeb promises to become a knowledge base that may eventually remove the need for user navigation all together 21 of 21 cstaff@cs.um.edu.mt