Papers in PDF format

W3DT and other Approaches to Hypermedia Application Design
Hypermedia design has to consider many different aspects as for example information structuring, navigational
design and interface design. Database design is a field very closely related to hypermedia design. Many formal
hypermedia design methodologies are based on well defined database design methods like the Entity-
Relationship model. In database design, models play a crucial role to express the intrinsic application oriented
data semantics. Some of the most popular hypertext design methodologies at present, like RMM, HDM or it's
successors HDM2 or OOHDM adopt modeling constructs of database design and add hypermedia related features
like navigational constructs see [Isakowitz et al. 1995], [Garzotto et al. 1993].This approach has been
chosen because it is familiar to system analysts. This is the main reason, why these methodologies are useful
for applications with highly structured information and high volatility (DBMS interface, product catalog).
On the other hand, practitioners tend to draw the nodes and links of their hypermedia applications in a relatively
straightforward manner in order to convert linear text into hypertext structures. The Web supports unstructured
information like multimedia news services as well as interfaces to databases or other kinds of structured
information. Thus a design method for WWW-based information systems requires representation of both.
W3DT provides the necessary modeling constructs to fill this gap. The notation is intentionally kept as simple
as possible to make W3DT easily comprehensible for the novice user.
Information Structuring and Navigation Design with W3DT
Since W3DT is designed for modeling WWW-sites, a Site is the broadest concept in W3DT. Each Site consists
of at least one Page and optional Links. Figure 1 shows the graphical representation of the elements in the
W3DT modeling technique and gives a short definition of each element.
Page
Menu
Index
Form
TPage
TMenu
TIndex
TPage
Link Dynamic Link
Diagram
Figure 1: Elements of the W3DT design methodology
Page, Index, Form and Menu are the basic means for structuring the information domain of a hypermedia
application. Note the difference between an Index and a Menu - the former is used to model a complete enumeration
of links, like a complete list of links to the members of a faculty. The latter is a navigational aid consisting
of links to other pages. An example is the homepage of a site. Its main purpose is not to give a complete
list of all its pages, but to give the user navigational aid and direct access to the main topics of the site.
Each of these design primitives can also be used as a Template (TPage, TForm, TIndex and TMenu). The
Template-notation is very similar to the concept of an Entity-Type in the Entity-Relationship model. The pages
created by a gateway-script querying a database are modeled by this construct. For example a TPage named
Faculty-Member can be used to denote similar descriptions of all the faculty-members. Usually, pages generated
by one gateway-script on the fly have the same layout, but the information displayed differs according to
the script's input arguments.
Links and Dynamic Links are used to model the Navigational Design of an application. Hardcoded links are
the standard way to navigate between WWW-pages. The Dynamic Link is slightly different - it represents the
execution of a gateway-script. All this leads to a rather simple rule: Links refer to static objects, Dynamic