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

Hypermedia
Fundamentals
Thanks to
Carole Goble
for slides
CM322
What is hypermedia?
Nodes and Links
Hypermedia application
characteristics
Navigation and non-linear reading
Hypermedia issues for the web
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.”
CM322
– Hypermedia and the Web , Lowe and Hall, 1999
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
Nodes, Links and Anchors

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

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
CM322 a source or destination of a link
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)
– Annotation on Links
– Dynamic Links to running applications
– Link Context
–
–
–
–
–

Maintenance
– Deletion Problem, dangling links, stranded nodes
CM322
Link types


Untyped links give too
much freedom? links as
“GOTOs”

– 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
CM322
Semantic link types:

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













Citation
– source,

pioneer, credit,
leads, eponym
Background
FutureWork
Refutation

Support

Methodology

Data

Generalize

Specialize

Abstraction

Example

Formalization

Application

CM322
Commentary Links

Argument
–
deduction,
induction,
analogy,
intuition
solution
Summarization
Detail
AlternateView
Rewrite
Explanation
Simplification
Complication
Update
Correction
Continuation
http://www.eastgate.com/HypertextNow/
archives/Trigg.html






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
Types of 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.
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

CM322
Instantiation of a semantic relationship
between information elements
 Links based meaning
 Cross referencing

Associative &
Referential links
Information space
Information Structures
CM322
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
Web hypermedia model



Not developed in the context of a formal model of
hypermedia
Simple node-link model
Links are simple
– Point to point
==> Plugins to provide multi-destinations
– Uni-directional
– Non-contextual
– Untyped

==> Applications provide a map of
interrelationships
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 –
CM322 –
dangling or obsolete links
Hypermedia issues for the Web
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

CM322
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
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
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












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
Hypermedia Navigation
"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 ...

CM322
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
CM322
http://www.eastgate.com/
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
Navigation on the Web?

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
CM322
Navigation & Context (1)
CM322
Navigation and Context (2)
CM322
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
Hypermedia issues for the Web
reprise
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

CM322
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
Link maintenance
notoriously difficult –
– dangling or obsolete
links
CM322

We were awarded an
excellent in <a href=
"http://www.qaa.ac.uk/re
vreps/subjrev/All/q23594.htm"> HEFCE's
Teaching Quality
Assessment exercise in
1994</a>.

<a
href="/Visitor_subweb/lo
cation.php3">Practical
information for those
visiting our buildings</a>
Generations of Hypermedia Systems
Xanadu, Augment,
Hypertext Editing
System/FRESS,
ZOG/KMS
Mainframe-based
Intermedia, NoteCards,
Hyperties
Workstation based KMS, Neptune, Guide (OWL),
HyperCard, Supercard,
PC-based
Microcosm, Microsoft
windows help system etc..
Standards and
Hypertext on the
reference models
internet
Dexter
WWW & Hyper-G
CM322
Open Hypermedia
Systems
Microcosm,
Webcosm, DeVise