Hypertext Model

1
Hypertext Model

• Hypertext is high-level interactive navigational
  structure
• allows us to browse text non-sequentially on
  computer screen
• consists of nodes which are correlated by
  directed links in graph structure
• each node may be text region like a chapter (in
  book), a section (in article), or a Web page

2
Hypertext Model (Cont.)

• two nodes A and B connected by directed link lAB
  which correlates texts associated with these two
  nodes
• reader might move to node B while reading text
  associated with node A
• hypertext link lAB attached to specific string
  inside text for node A
• such string marked (different color or
  underlined) to indicate presence of underlying
  link
• if such string clicked, the underlying directed
  link is followed and new text region (for node at
  destination) is displayed on screen

3
Hypertext Model (Cont.)

• Process of navigating hypertext is traversal of
  directed graph
• linked nodes of graph represent text nodes that
  are semantically related
• when hypertext large, user might lose track of
  structure of hypertext
• lost in hyperspace problem
• include hypertext map to solve problem
• directed graph which displays current node
  visited
• include information on paths traveled so far

4
About the Web

• Hypertexts provide basis for design of hypertext
  markup language (HTML) and hypertext transfer
  protocol (HTTP) which originated the Web
• Web not proper hypertext since it lacks
  underlying data model, navigational plan and
  consistently designed user interface
• Web is pool of (partially) interconnected webs
• some webs are hypertext others are collection of
  pages designed separately

5
Trends and Research

• User of Web (frequently) does not know what he
  wants
• difficulty in formulating request
• research in advanced user interface highly
  desirable
• indexes maintained by various Web search engines
  almost disjoint
• e.g. ten most popular search engines have indexes
  whose intersection is lt 2 of total no. of pages
  indexed
• research on meta-search engine (fusing rankings
  generated by other search engines) promising