Open Hypermedia Examples

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Open Hypermedia Examples

• Microcosm
• The Distributed Link Service (DLS)

Thanks to
Les Carr
Hugh Davis
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Microcosm

• Developed in 1987
• Used for educational applications
• Pioneered resource-based authoring paradigm
• Commercialised http//www.multicosm.com

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Microcosm

• Documents handled by document management system
• Viewers were handled by a presentation control
  system
• Hypermedia services layer mediated the two and
  allowed linking between documents

Authoring Tools
Database
Spread sheet
Word Processor
Presentation Systems
Hypermedia Link Services
Document Management System
Text Files
Video Files
Image Files
Audio Files
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Microcosm Links

• Microcosm links are stored in databases and refer
  to the anchors as a triple
• DMS document id (not filename)
• position in document (byte offset)
• Document contents at that position (selection)
• Most links are invisible
• Select a word, choose follow link from a menu
• Link following is like a query
• Can you tell me more about this part of the
  document?

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Finding invisible links on a single word.
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TheMicrocosm Model
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Opening a Document

• A viewer sends a message asking for a document to
  be opened
• The document management system (DMS) responds by
  sending a message for a viewer to be dispatched
  with a particular file
• The viewer displays the contents and send a
  message asking for all the visible links
  (buttons) associated with this document
• Many linkbases (aka filters) respond with
  messages describing links that they discovered.
• As each message returns, the viewer redisplays
  the relevant portion of text appropriately
  highlighted.

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Filters

• In the hypermedia services layer, filters receive
  and send Microcosm messages.
• Linkbases are an example of a filter
• All filters are arranged in a chain
• All messages are seen by all filters downstream
  
• On receiving a message, a filter might
• return it without taking any further actions
• change it
• block it
• return further new messages.

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Filters

• A filter might
• receive a Follow Link request and generate a
  number of Despatch Document messages
• Receive a Follow Link message and use a
  thesaurus to also generate a number of extra
  Follow Link
• e.g. a request on right-wing might also trigger
  links on fascist and conservative
• Suppress all but the most important dispatch
  document requests

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Link Types

• Specific Links
• link from a particular piece of text at a
  particular position in a particular document
• Local Links
• link from a particular piece of text anywhere in
  a particular document
• Generic Links
• link from a particular piece of text anywhere in
  any document (the Docuverse)

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Link Types
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Multimedia Linking

• MAVIS project

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Remarks on Microcosm Model

• Advantages
• Generic Link turns out to be a simple idea but
  very powerful
• Greatly eases the problems of information reuse
  and maintenance
• Disadvantages
• Heavyweight system architecture
• Many processes required
• Many messages passed
• Early versions of Windows found it difficult to
  cope!
• Original software core was 16 bit
• commercialisation pressures made it difficult to
  advance facilities and re-implement core

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Resource Based Authoring

• Microcosm, and its generic link mechanism,
  pioneered Resource Based Authoring.
• RBA is the natural authoring paradigm of an open
  hypermedia system
• create a set of independent resources
• use different systems for each resource (as
  appropriate)
• integrate them using sets of link databases

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Resource-based Authoring
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Resource-based Authoring

• Note that the creation of the content (web pages,
  videos, simulations etc) is
• INDEPENDENT
• of the creation and deployment of the links
• THANKS TO
• the use of a separate linking process

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Resource-based Authoring

• Adapt the integrated information resource for
  different audiences by
• Using different linkbases
• Chosen according to user profile
• E.g.
• simple explanatory links for first year
  undergraduates
• vs links to in depth reading and further
  challenges for PhD students

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STOMP

• Software Teaching of Modular Physics
• project funded by TLTP program in 1994
• used for teaching in a number of UK universities
• successfully integrated diverse teaching
  resources
• textbooks, lectures, audio, video simulations
• Excellent example of resource-based authoring
• Microcosms generic links linked from materials
  after they were written

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STOMP is a library
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STOMP is a hypertext
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STOMP is an interactive textbook
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Distributed Link Service

• Distributed Link Service is an implementation of
  Microcosms generic links for the Web
• Can add links to the users view of other
  peoples Web pages
• On the fly (using a proxy or intermediary)
• In batch as a Web site construction tool
• Commercialised as
• WebCosm
• Portal Maximiser
• http//www.multicosm.com/
• http//www.bib.ecs.soton.ac.uk/records/1440

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Distributed Linking Service (DLS)

• Use proxy server to add links on the fly while
  the user browses
• Application, presentation and behaviour of links
  is under user control
• Automatically link on phrases or other standard
  document features e.g. citations

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DLS Architecture
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DLS Controller
Collections of links to include while browsing
Options for presenting links.
What should a link look like?
What should a link do when you click it?
Only display important links, or use colour to
highlight them.
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DLS In Action (1)

• Original document, unlinked in pristine condition

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DLS In Action (2)

• Document linked in plain style

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DLS In Action (3)

• Document linked in bibliographic style

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DLS In Action (4)

• Link priorities distinguished by colour scheme

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Link Behaviours

• More than just click and go semantics

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Citation Linking (1)

• Pristine extract of an academic paper

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Citation Linking (2)

• DLS adds links to citations on the fly by using a
  sophisticated pattern recogniser.

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Citation Linking (3)

• The citations are internally linked to the
  articles own bibliography

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Citation Linking (4)

• which is linked to an independent bibliographic
  database (or the cited article itself, if it is
  available).

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Open Hypermedia and the Web

• The web consists fundamentally of
•         The server
•         http
•         html (now xml)
•         The browser
• The server is open it has an interface by which
  applications may access its services.
• Http is open in that you can always hang new bits
  off the end (http NG will be more open)
• Html was not open, but XML allows you to invent
  your own style sheets, embed RDF etc.
• Browsers allow plugins, and are anyway made of
  COM objects.

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Open Hypermedia and the Web

• But what are the services?
• There is no hypertext on the server. All
  hypertext is dependant on one (closed) data
  format (html)  
• The server is an internet file server.
• The Web is sufficiently open that it could be
  made into a hypertext system. (DLS/WebCosm)
• It is difficult to make and maintain links in
  HTML documents
• It is difficult to create complex and flexible
  navigation structures

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XLink Web Open Linking

• XLink defines an Open Hypermedia-style for Web
  links
• links can have multiple anchors
• links can be stored in databases
• a few kinds of implicit behaviour semantics are
  defined
• not yet used!
• Based on XML and XPointer

http//www.sun.com/software/xml/enterprise/xlink.h
tml http//www.cs.brown.edu/memex/ACM_HypertextTes
tbed/papers/47.html