Hypermedia Fundamentals Thanks to Carole Goble for slides

Hypermedia Fundamentals Thanks to Carole Goble for slides CM 322 What is hypermedia? Nodes and Links Hypermedia application characteristics Navigation and non-linear reading Hypermedia issues for the web

What is Hypermedia? l 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. ” l Hypertext: “Text which is not constrained to be linear” l – World Wide Web consortium, ‘Hypertext Terms’, April 1995 l “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. ” CM 322 – Hypermedia and the Web , Lowe and Hall, 1999

What is Hypermedia? l Non-linear writing – Interlinked texts – Multiple pathways, multiple reading sequences – Multiple media: video, audio, images, emails, databases, spreadsheets Annotation and commentary l Association of ideas l Writing and reading not separated l Interactive l CM 322

Nodes, Links and Anchors l Node represents ‘chunk’ of information corresponding to a natural ‘semantic unit’ – e. g. screen, page, frame … – The act of chunking information is part of authoring process l Link represents an association between nodes – Machine-supported fast inter-node connections l 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 CM 322 a source or destination of a link

Hypermedia Linking Links are first class citizens l Mechanics l 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) – Annotation on Links – Dynamic Links to running applications – Link Context – – – l Maintenance – Deletion Problem, dangling links, stranded nodes CM 322

Link types l l Untyped links give too much freedom? links as “GOTOs” l – Subclass/superclass hierarchies – Supports/opposes source node – Is an example of source node GUIDE hypertext system had: – Pop-up footnote links – Replacement (“fold-out”) Hierarchic links – Reference links for free associations – Mouse cursor feedback on link type CM 322 Semantic link types: l Use – Filter on type to cut down complexity – Automatically process link types as part of an intelligent hypermedia application

Taxonomy of semantic link types Normal Links l l l l Citation – source, l pioneer, credit, leads, eponym Background Future. Work Refutation l Support l Methodology l Data l Generalize l Specialize l Abstraction l Example l Formalization l Application l CM 322 Commentary Links l Argument – deduction, induction, analogy, intuition solution Summarization Detail Alternate. View Rewrite Explanation Simplification Complication Update Correction Continuation http: //www. eastgate. com/Hypertext. Now/ archives/Trigg. html l l l Comment – critical, supportive Related. Work – misrepresents, vacuum, ignores, is. Superseded. By, is. Refuted. By, is. Supported. By, redundant Problem. Posing – 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

Types of information Structural links Organisational space Provides a link between an item of information and an elaboration or explanation of that information. l The item at one end of a referential link exists because of the existence of the other item. l E. g. a link from a word to its definition. Provide a form for the information space l Allow user to develop an understanding of its scale and their location within the space l Do not imply any semantic relationships between linked information l l CM 322 Instantiation of a semantic relationship between information elements l Links based meaning l Cross referencing l Associative & Referential links Information space

Information Structures CM 322

Info (Link) structures depend on l CONTENT – Material & structure underlying – Volatility of material – Access paths l CONTEXT – How is it to be used? – Who by? – Where have they been before? CM 322

Web hypermedia model Not developed in the context of a formal model of hypermedia l Simple node-link model l Links are simple – Point to point ==> Plugins to provide multi-destinations l – Uni-directional – Non-contextual – Untyped ==> Applications provide a map of interrelationships l Nodes are complex media compositions – – l 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 – CM 322 – dangling or obsolete links

Hypermedia issues for the Web l l l 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 CM 322

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 l 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… CM 322

Hypermedia Application Characteristics Functional and non functional characteristics l E. g. Follow a link from one page to another l – Expectation of navigation by browser FUNCTIONAL – Expectation of relevance and correctness once link navigated l NON FUNCTIONAL l CM 322

Functional Characteristics l l l l l 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 CM 322

l l l Non functional Characteristics Link 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 CM 322

Hypermedia Navigation l l l "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. . . CM 322

Non-linear reading How are hypertext information systems different from traditional “linear” paper-based presentations (eg books) ? l “The rhetoric of arrival and departure” - Landow l – 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? l MORE CONTEXT AND INFO ON LINKS CM 322 http: //www. eastgate. com/

Lost in Hyperspace (Conklin 87) Problems of disorientation and navigation in large hyperspaces (Nielsen 1995: Multimedia and Hypertext) l More reader/user choice l Some control passed from author to reader l but with greater choice comes l – more cognitive overhead – Lost in Hyperspace problem l Need for: – ==> System-generated ways of orienting the reader – Feedback of location (orientation cues) – Effective navigation tools CM 322

Navigation on the Web? l Web has evolved some navigation tools: – – – l 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 l popup annotation or basic URL address at bottom l some interactivity But navigation is hampered by the poor link model, poor navigation instruments and poor design CM 322

Navigation & Context (1) CM 322

Navigation and Context (2) CM 322

Issues in hypermedia l Location of information – Primitive manual authoring of static links l Users context – Developing an understanding and responding Information contextualisation l Support for l – intelligent browsing and navigation, – information structuring, – mechanisms for active annotation – restructuring of networks based on feedback. CM 322

Hypermedia issues for the Web reprise l l l 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 CM 322

Links are not first class reprise 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 l Link maintenance notoriously difficult – – dangling or obsolete links l CM 322 l We were awarded an excellent in <a href= "http: //www. qaa. ac. uk/re vreps/subjrev/All/q 23594. htm"> HEFCE's Teaching Quality Assessment exercise in 1994</a>. l <a href="/Visitor_subweb/lo cation. php 3">Practical information for those visiting our buildings</a>

Generations of Hypermedia Systems Xanadu, Augment, Hypertext Editing System/FRESS, ZOG/KMS Mainframe-based Intermedia, Note. Cards, Hyperties Workstation based KMS, Neptune, Guide (OWL), Hyper. Card, Supercard, PC-based Microcosm, Microsoft windows help system etc. . Standards and Hypertext on the reference models internet Dexter WWW & Hyper-G CM 322 Open Hypermedia Systems Microcosm, Webcosm, De. Vise