Hypermedia is an interactive, nonlinear medium where data are represented by
nodes and links. It is an elaborated form of hypertext. The terms hypertext
and hypermedia were coined by Ted Nelson in the early 1970s. He envisioned
a system called Xanadu (Nelson, 1974), where all the literature
of the world would be linked together in a gigantic world-wide distributed database.
Annotations and cross-references would make it possible to browse through the
literature quickly and easily. The difference between hypertext and hypermedia
is that hypermedia in addition to text makes use of other forms of representations,
like pictures, animations and sound. Hypermedia provides a mechanism that allows
users to store, manipulate and communicate information as interactive documents
and has become an essential element in a wide variety of computer applications,
such as the World Wide Web (WWW), electronic commerce systems, computer-based
learning systems and so forth (Lin, 2003a).
The characteristics of the non-linear form of hypermedia are indeed different
from printed media. Hypermedia allows users to access the material in many different
ways and to jump to different information items, since the user has been provided
with the necessary links. Although, hypermedia allows rapid nonlinear access
to large amounts of information and extends the users control by giving
them the freedom to explore documents according to their information needs (Conklin,
1987), there is little evidence to suggest that users can in practice, benefit
from the degree of freedom that hypermedia provides in searching for information.
Indeed, researchers have indicated that the major limiting factor of hypermedia
has been that users often get lost or disoriented due to the topological complexity
(McDonald and Stevenson, 1998; Kim, 1999).
The disorientation problem in the use of hypermedia can be characterized as
the Art Museum Phenomena (Foss, 1989). The Art Museum
Phenomena refers to the problems associated with hypermedia browsing, an open
information-seeking activity in a nondirective manner. During this activity,
users may be unable to recognize which nodes have been visited or which parts
remain to be seen, as a result of nonspecific wandering in the hyperlink-based
Kim (1999) stated that in order to solve the disorientation
problem in hypermedia systems, the structure of hypermedia topology should be
considered. Two common structures of topology in the use of hypermedia are hierarchical
and network topologies (Shin et al., 1994). As
the names suggest, hierarchical structures allow the nodes to be connected to
form a strict hierarchy, where a node at one level can only access nodes directly
above or below.
These structures contain organizational links (Locatis
et al., 1989). Nonetheless, network structures allow a node to be
connected to any other node in the hypertext to form a complex structure with
many links, often referred to as referential links (Locatis
et al., 1989). McDonald and Stevenson (1998)
examined the effects of hierarchical and network topologies on users navigation
performance compared to a linear version of the same document. The results of
the study showed that there was no significant difference between the hierarchical
and network topologies. However, a nonlinear topology, which took the form of
multiple data linkage was more likely to result in disorientation than its organizational
counterparts data connection built on linear topology. In two other studies
(Lin, 2003a, b) researchers
examined the effects of hierarchical and network topologies on older users
navigation performance. The results showed that for older adults, hypertext
with a hierarchical topology was superior to its referential counterpart in
terms of browsing and navigation efficiency.
According the results generated from the previous studies mentioned above (McDonald
and Stevenson, 1998; Lin, 2003a, b),
the position is unclear as to which structure is more likely to be easy to use
and to enhance navigation. Furthermore, while scrutinizing the nonlinear topology
of their studies, it was found that different forms of network topology were
used in their studies. In the study of McDonald and Stevenson
(1998), the nodes in the document were linked to form a network based on
a number of cross-referential links in which any node could be connected to
any other node.
A link was established, via keywords or text buttons in the text of each node
to other related nodes; the positions and arrangements of the links within each
node were placed according to the content of the text itself. Therefore, the
different text contents produced different positions and arrangements of the
links. In contrast, the studies of Lin (2003a,
b) integrated all the links in the same position and order for each node.
However, the links of a node can only connect to some nodes instead of to any
Combining the above mentioned points, a hypothesis was generated: If a network topology could be constructed with links that connect to all the other nodes and all the links were arranged in the same position and order for each node, the users navigation performance be better. Consequently, a different form of network topology, which was inspired by past research was examined to discover its effect on users navigation performance in comparison to both traditional linear and hierarchical topologies in the present study.
MATERIALS AND METHODS
Participants: Eighteen undergraduates at a local university, who had >1 year of constant web browsing experience, participated in the experiment. Their ages ranged from 18-36 years old (M = 21.6, SD = 3.7), respectively.
Materials: The experimental materials were three sets of car-show web
pages. The three web pages were programmed by Hypertext Markup Language (HTML)
based on three different hypermedia topologies: linear, hierarchical and network.
Each of the three sets of documents provided 15 different car-show web pages.
Each web page represented one node in the hypermedia systems and the contents
for every node comprised two car pictures, one animation between the two pictures
and a 100 words description on average of 14-point traditional Chinese Ming
characters. The linear document had a sequential structure of the 15 nodes with
14 links (Fig. 1); each node appeared in a fixed linear sequence.
Movement through the document was achieved by means of clicking on Next and
Previous buttons on the bottom of the web pages, which caused the next or previous
web page to be displayed.
The links of the web pages in the hierarchical document were based on one parent
node for two child nodes, resulting in the 15 nodes with 14 links (Fig.
2). Participants moved through the document by clicking on the text buttons
on the bottom of the web pages. Clicking on the text button caused a web page
bearing the same name as the button to be displayed. The document included a
backtrack facility. The web pages in the network document were based on 210
cross-referential links in which each web page could be connected to every other
web page. The links were established via text buttons shown on the bottom of
the web pages (Fig. 3). The document also included a backtrack
facility. All of the three sets of documents were run on the Microsofts
IE browser 6.0 and were displayed with a 17-in. LCD color monitor. Participants
activities were monitored throughout the experiment.
Experimental design: A between subjects single factor experimental design
was adopted in this study. The independent variable was hypermedia topology,
i.e., hierarchical, network and linear. The dependent variables were the mean
time of locating specific nodes and the mean number of nodes opened during browsing
(Shin et al., 1994). Participants were randomly
assigned to one of the three experimental conditions.
Procedure: At the beginning of the experiment, each participant was
asked to complete a questionnaire regarding his or her computer experience.
To ensure an equivalent level of interaction, each participant was then provided
with an explanation on how to use the hypermedia document. Any questions the
participant had were answered before the experiment. Participants were also
asked to browse through the web pages as much as possible during a period of
10 min. After 2 min rest, participants were then required to use the hypermedia
document to answer seven questions. Each participant received the same seven
|| The linear type of hypermedia topology
|| The hierarchical type of hypermedia topology
|| The network type of hypermedia topology
|| The self-assessment manikin
The answers to the questions could be found in specific nodes in the document.
Participants were instructed to navigate through the hypermedia document to
locate the answers. Once they had located the answer to a question, they reported
their response to the experimenter. They were then given the next question.
The presentation order for the seven questions was randomly assigned to each
participant. Each question was printed on a card and was handed to the participant
by the experimenter. The time taken to find the answers and the number of opened
nodes were recorded. After answering the seven questions in order to elicit
information about the quality of the participants interaction, each participant
was asked to rate their preferences according to their perceptions concerning
their navigation experience in using a Self-Assessment Manikin (SAM) (Fig.
4). The SAM is a nonverbal method for quickly assessing preference associated
with an individuals emotional reaction to an event (Mehrabian
and Rusell, 1977). The preference scale ranges from 1-9; 1 indicates an
unpleasant mood-mostly dislike, 9 indicates a very pleasant mood-mostly like
and 5 indicates a neutral mood. This scale corresponds to pictures of the SAM
figure that range from smiling and happy to frowning and unhappy.
RESULTS AND DISCUSSION
The descriptive statistics of the topological effects on the navigation performance measures pertinent to the mean time of locating specific nodes and the mean number of nodes opened are shown in Table 1.
Mean time of locating specific nodes: The total time taken to answer the seven questions using the hypermedia document was calculated for each participant. The mean time per condition is shown in the top row of Table 1.
||Mean time per condition (in sec) and the mean number of nodes
opened for the question answering task
|| Mean preference rating for the three different hypermedia
The results generated from the one-way ANOVA revealed a significant effect
of subject group (F2,33 = 15.22, p<0.01). Tukey HSD tests also
indicated that participants in the network condition answered the questions
significantly faster than did the participants both in the hierarchical and
linear conditions. There was no significant difference between the hierarchical
condition and the linear one.
Number of nodes opened: The number of nodes opened by each participant to locate the answers for the seven questions was calculated. The mean number of nodes opened for each of the three conditions is shown on the bottom row of Table 1. The results from the one-way ANOVA indicated a significant effect of subject group (F2,33 = 22.40, p<0.01). Tukey HSD tests indicated that participants in the network condition opened significantly fewer nodes than did those in either in the hierarchical and linear conditions. There was no significant difference between the hierarchical and linear conditions.
Preference rating: The descriptive statistics of the topological effects on the SAM questionnaire are shown in Table 2. The SAM data were analyzed using a Kruskall-Wallis test. The test indicated significant differences among the three groups (X2 = 9.28, p = 0.01).
Further analysis, using Mann-Whitney tests indicated that more participants using the network document rated themselves as having a significantly positive experience than did those in the hierarchical condition (Z = -3.03, p = 0.002). There was no significant difference between the hierarchical and linear conditions or between the network and linear conditions.
The purpose of this study is to explore the effects of different hypermedia
topologies on users navigation performance. According to the outcomes
of this study, the results supported the proposition by Conklin
(1987) that network topology of hypermedia distinguishes itself from traditional
linear information processing in aspects of rapid nonlinear information access
and higher level of control in document exploration.
||The comparison of two different network topologies, (a) incomplete
network topology and (b) complete network topology
However, most previous studies argued that this same benefit of nonlinear information
seeking led to difficulty in user orientation (McDonald
and Stevenson, 1998; Lin, 2003a, b,
2004). In the present study, three different topologies
were examined and the results showed that the form of the network topology used
in this study was not reported as associated with participant disorientation.
Moreover, participants navigation performance in the network topology
was significantly better than in both the linear and hierarchical topologies.
Some explanations as follow, may account for the differences among this study
and the past research studies (McDonald and Stevenson, 1998;
Lin, 2003a, b, 2004).
The study conducted by McDonald and Stevenson (1998)
examined the effects of hierarchy and nonlinear topologies on navigation performance
and compared them to a linear version of the same document.
The results showed that participants performed better with the linear text
than with the nonlinear text, while performance on the hierarchical document
fell between these two extremes. Regarding the nonlinear topology of their study,
the nodes in the document were linked to form a network based on a number of
cross-referential links, whereby any node could be connected to any number of
other nodes. A link was established via keywords or text buttons in the text
of each node to other related nodes, so that the positions and arrangements
of the links on each hypertext were placed according to the content of the text
Therefore, the different text contents produced different positions and arrangements of the links. Consequently, users had to search for their needed links within the text contents. Thus, users had to simultaneously focus on reading the text information to find the answers for the questions and searching for the target links within the text in order to orient themselves within the hyper-textual space. Regarding the network topology used in this study, the links were arranged at the bottom of each web page in the same position and in the same order. Users did not have to search for the desired links, while simultaneous reading the information.
In studies by Lin (2003a, b,
2004), user performance in the hierarchical topology was also significantly
superior to that in the network topology. The structure of network topologies
used in their studies were incompletely constructed (Fig. 5).
For instance, the network topology which was used in the study by Lin
(2003a), mimicked the real world gigantic WWW database structure. The links
of each web page could not connect to all other nodes. Within this incomplete
network structure, users could not foresee the relationships among different
In the present study, users knew that any node could be connected to any number of other nodes. Therefore, users did not need to use extra mental resources to memorize the relationships between links and nodes.
These two arguments regarding the different forms of network topologies used in the present study and past research studies mentioned before, would clarify the different results for the effects of the network topology on users navigation performance. Regarding the subjective preference rating, the analysis of the SAM questionnaire data indicated a similar trend in user performance. More participants who had used the network document reported having experienced significantly positive mood and preference than did participants who had used the linear and hierarchical documents.
The difference in performance among the linear, hierarchical and non-linear conditions may be accounted for by the disparate amount of choice offered to the user in terms of the number of links and directions whereby they had freedom to browse.
The network structure places no constraints on user movements. That is, users have unlimited freedom to explore a richly connected network of ideas. Again, this result was different from the results of previous studies. The reasons for the differences are similar to the reasons mentioned above. The complete network structure placed the freedom to travel on the web pages and without the resulting disorientation.
Past research studies indicated that the network topology of hypermedia allows
rapid access to large amounts of information and extend users control,
giving them the freedom to explore the documents according to their information
needs. However, researchers commented that hypermedia users often got lost or
became disorientation within this nonlinear topology. However, the result of
this study indicates that there might be a specific circumstance for traveling
efficiently and freely within the hypermedia network topology without disorientation
or a higher cognitive burden placed on the user in terms of the availability
of memory resources. According to the results generated from this study and
comparing the different forms of network topologies used in this and previous
research studies, the implications for designing an efficiently network topology
should be as follows: each node within a network topology of hypermedia should
have links completely connecting it to any other node and all the links of each
web page should be arranged in the same order and position. Following these
two suggestions, users may gain the freedom to explore the network topological
documents according to their information needs, without experiencing any disorientation.