Hypermedia Fundamentals

1. HypermediaFundamentals Thanks to Carole Goble for slides What is hypermedia? Nodes and Links Hypermedia application characteristics Navigation and non-linear reading Hypermedia issues for the web CM322

2. What is Hypermedia? • Hypertext: “a combination of natural language text with the computer’s capacity for branching, or dynamic display • Ted Nelson, 1967 • Hypermedia: “multimedia hypertext. Hypermedia and hypertext tend to be used loosely in place of each other. Media other than text typically include graphics, sound and video.” • Hypertext: “Text which is not constrained to be linear” • World Wide Web consortium, ‘Hypertext Terms’, April 1995 • “An application which uses associative relationships among information contained within multiple media data for the purpose of facilitating access to, and manipulation of, the information encapsulated by the data.” • Hypermedia and the Web , Lowe and Hall, 1999 CM322

3. What is Hypermedia? • Non-linear writing • Interlinked texts • Multiple pathways, multiple reading sequences • Multiple media: video, audio, images, emails, databases, spreadsheets • Annotation and commentary • Association of ideas • Writing and reading not separated • Interactive CM322

4. Nodes, Links and Anchors • Noderepresents ‘chunk’ of information corresponding to a natural ‘semantic unit’ • e.g. screen, page, frame … • The act of chunking information is part of authoring process • Link represents an association between nodes • Machine-supported fast inter-node connections • Anchor represents a link on a node • e.g. buttons, bolded text, “hotspots”, images … • the whole node might be an anchor but should be able to designate a sub-region as a source or destination of a link CM322

5. Hypermedia Linking • Links are first class citizens • Mechanics • Single or multi- source / single or multi-destination • Uni- / bi- directional • Anchoring: generic links, dynamic links … • Versioning & Composites & Virtual structures • Computed Links (search and query on keywords or calculated from interests or ‘trail’ so far) • Annotationon Links • Dynamic Links to running applications • Link Context • Maintenance • Deletion Problem, dangling links, stranded nodes CM322

6. Untyped links give too much freedom? links as “GOTOs” GUIDE hypertext system had: Pop-up footnote links Replacement (“fold-out”) Hierarchic links Reference links for free associations Mouse cursor feedback on link type Semantic link types: Subclass/superclass hierarchies Supports/opposes source node Is an example of source node Use Filter on type to cut down complexity Automatically process link types as part of an intelligent hypermedia application Link types CM322

7. Normal Links Citation source, pioneer, credit, leads, eponym Background FutureWork Refutation Support Methodology Data Generalize Specialize Abstraction Example Formalization Application Commentary Links Comment critical, supportive RelatedWork misrepresents, vacuum, ignores, isSupersededBy, isRefutedBy, isSupportedBy, redundant ProblemPosing trivial, unimportant, impossible, ill-posed, solved, ambitious Thesis trivial, unimportant, irrelevant, redherring, contradict, dubious, counterexample, inelegant, simplistic, arbitrary, unmotivated Argumentation invalid, insufficient, immaterial, misleading, alternative, strawman Data inadequate, dubious, ignores, irrelevant, inapplicable, misinterpreted Style boring, unimaginative, incoherent, arrogant, rambling, awkward Taxonomy of semantic link types • Argument • deduction, induction, analogy, intuition solution • Summarization • Detail • AlternateView • Rewrite • Explanation • Simplification • Complication • Update • Correction • Continuation http://www.eastgate.com/HypertextNow/archives/Trigg.html CM322

8. Types of information • Provide a form for the information space • Allow user to develop an understanding of its scale and their location within the space • Do not imply any semantic relationships between linked information Structural links Organisational space • Provides a link between an item of information and an elaboration or explanation of that information. • The item at one end of a referential link exists because of the existence of the other item. • E.g. a link from a word to its definition. • Instantiation of a semantic relationship between information elements • Links based meaning • Cross referencing Associative & Referential links Information space CM322

9. Information Structures CM322

10. Info (Link) structures depend on • CONTENT • Material & structure underlying • Volatility of material • Access paths • CONTEXT • How is it to be used? • Who by? • Where have they been before? CM322

11. Web hypermedia model • Not developed in the context of a formal model of hypermedia • Simple node-link model • Links are simple • Point to point • Uni-directional • Non-contextual • Untyped • Nodes are complex media compositions • Browser frames – improve contextualisation of info • Java applets – improve integration of media • VRML, QT – broaden range of media • Plug ins – improve browser functionality • Link maintenance notoriously difficult – • dangling or obsolete links ==> Plugins to provide multi-destinations ==> Applications provide a map of interrelationships CM322

12. Difficult to add own personal links to a WWW document without making a copy (and losing updates) Difficult to offer different link sets for different purposes – eg Level I links, Level III links, my own links Difficult to provide computed links in a standard way – dependent on some automatic computation Difficult to adaptively present web documents in different ways for different readers No standard non-proprietary support for hyperlinking between different desktop applications Hypermedia issues for the Web CM322

13. Hypermedia Application Goals “To support (using the associative relationships between information sources) the carrying out of actions which: … result in the identification of … … facilitate the effective utilisation of … … result in control of … appropriate information (with appropriateness being based on a given set of contextually defined criteria)” • Lowe and Hall, 1999 • Hampered or aided by hypermedia and presentation systems • E.g. Web means you can’t use generic links, multiple destination links, overlapping link anchors etc… CM322

14. Hypermedia Application Characteristics • Functional and non functional characteristics • E.g. Follow a link from one page to another • Expectation of navigation by browser • FUNCTIONAL • Expectation of relevance and correctness once link navigated • NON FUNCTIONAL CM322

15. Functional Characteristics • Navigability • Orientation – • Information maps and overviews • Information trails • Information Contextualisation • Searching and Indexing • Document management • Information Security and cost • Presentation • Customisability • Effective use of resources • Handling of temporal data CM322

16. Non functional Characteristics • Link validity, correctness, relevance, completeness and integrity • Content validity, correctness, relevance, completeness and integrity • Content organisation • Consistency and seamlessness • Efficiency • Maintainability and evolvability • Reusability • Reliability and Robustness • Testability, validation and verification • Interoperability, flexibility, portability, genericity • Political and social aspects • Cost effectiveness CM322

17. "Rhetoric of arrival and departure” "The very existence of links in hypermedia conditions the reader to expect purposeful, important relations between linked materials ...... George Landow ... those documents that disappoint these expectations appear particularly incoherent and nonsignificant ..… ... Books permit the student reader to avoid apparently nonsignificant or insignificant materials - one simply glances at them and turns the page .… ... Hypermedia linking is a double-edged sword that offers readers information in new, more efficient ways but ... simple linking has capacity to confuse and leave readers ... Hypermedia Navigation CM322

18. Non-linear reading • How are hypertext information systems different from traditional “linear” paper-based presentations (eg books) ? • “The rhetoric of arrival and departure” - Landow • Where am I? • How do I get back to 5 screens ago? • How do I get to XXX? • What is the quickest way of getting to XXX? • How can I find out more about this topic? • What happens if I follow this link? • How much information follows this link? • Where have I come from? • How do I get back? • Who has been here before? • MORE CONTEXT AND INFO ON LINKS http://www.eastgate.com/ CM322

19. Lost in Hyperspace (Conklin87) • Problems of disorientation and navigation in large hyperspaces (Nielsen 1995: Multimedia and Hypertext) • More reader/user choice • Some control passed from author to reader • but with greater choice comes • more cognitive overhead • Lost in Hyperspace problem • Need for: • ==> System-generated ways of orienting the reader • Feedback of location (orientation cues) • Effective navigation tools CM322

20. Web has evolved some navigation tools: conventional back links feedback on previously selected links bookmarks (but difficult to organise) history trail portals/link indexes rollover annotation on links gives some context popup annotation or basic URL address at bottom some interactivity But navigation is hampered by the poor link model, poor navigation instruments and poor design Navigation on the Web? CM322

21. Navigation & Context (1) CM322

22. Navigation and Context (2) CM322

23. Issues in hypermedia • Location of information • Primitive manual authoring of static links • Users context • Developing an understanding and responding • Information contextualisation • Support for • intelligent browsing and navigation, • information structuring, • mechanisms for active annotation • restructuring of networks based on feedback. CM322

24. Difficult to add own personal links to a WWW document without making a copy (and losing updates) Difficult to offer different link sets for different purposes – eg Level I links, Level III links, my own links Difficult to provide computed links in a standard way – dependent on some automatic computation Difficult to adaptively present web documents in different ways for different readers No standard non-proprietary support for hyperlinking between different desktop applications Hypermedia issues for the Webreprise CM322

25. Links are embedded in the content No separate link database or link layer (hence XLink) Difficult to visualise all links separately or automatically process them Link maintenance notoriously difficult – dangling or obsolete links We were awarded an excellent in <a href= "http://www.qaa.ac.uk/revreps/subjrev/All/q235-94.htm"> HEFCE's Teaching Quality Assessment exercise in 1994</a>. <a href="/Visitor_subweb/location.php3">Practical information for those visiting our buildings</a> Links are not first classreprise CM322

26. Generations of Hypermedia Systems • Xanadu, Augment, Hypertext Editing System/FRESS, ZOG/KMS Mainframe-based • Intermedia, NoteCards, Hyperties • KMS, Neptune, Guide (OWL), HyperCard, Supercard, Microcosm, Microsoft windows help system etc.. Workstation based PC-based Standards and reference models Dexter Hypertext on the internet WWW & Hyper-G Open Hypermedia Systems Microcosm, Webcosm, DeVise CM322