Contextual Navigation Aids for Two World Wide Web ... - CiteSeerX

INTERNATIONAL JOURNAL OF HUMAN–COMPUTER INTERACTION, 12(2), 193–217 Copyright © 2000, Lawrence Erlbaum Associates, Inc.

Contextual Navigation Aids for Two World Wide Web Systems Joonah Park Jinwoo Kim Human Computer Interaction Lab Department of Cognitive Science Yonsei University

In spite of the radical enhancement of Web technologies, many users still continue to experience severe difficulties in navigating Web systems. One way to reduce the navigation difficulties is to provide context information that explains the current situation of Web users. In this study, we empirically examined the effects of 2 types of context information, structural and temporal context. In the experiment, we evaluated the effectiveness of the contextual navigation aids in 2 different types of Web systems, an electronic commerce system that has a well-defined structure and a content dissemination system that has an ill-defined structure. In our experiment, participants answered a set of postquestionnaires after performing several searching and browsing tasks. The results of the experiment reveal that the 2 types of contextual navigation aids significantly improved the performance of the given tasks regardless of different Web systems and different task types. Moreover, context information changed the users’ navigation patterns and increased their subjective convenience of navigation. This study concludes with implications for understanding the users’ searching and browsing patterns and for developing effective navigation systems.

1. INTRODUCTION The rapid growth of the Internet has created new lifestyles, such as searching for valuable information and browsing through various products by using the World Wide Web (WWW) as a universal tool. However, users have been found to experience severe difficulties in using the WWW for various kinds of tasks within numerous Web sites (Carmel, Crawford, & Chen, 1992; Kim & Hirtle, 1995). For example, users cannot identify where they are, cannot return to previously visited locations, This research was supported by the Korean Institute of Information Technology Assessment grant No. 99–10. Requests for reprints should be sent to Joonah Park or Jinwoo Kim, Human–Computer Interaction Lab, Department of Business Administration, College of Economics and Management, Yonsei University, 120–749, Korea. E-mail: [email protected] or [email protected]

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and cannot remember the key points they have learned during their navigation (Theng, Thimbleby, & Jones, 1996). These difficulties have been summarized as “lost in hyperspace” phenomenon, which is classified as either disorientation or cognitive overhead (Conklin, 1987). Disorientation is defined as “the tendency to lose one’s sense of location and direction in a nonlinear document” (Conklin, 1987, p. 40). There are four kinds of disorientation that are particularly relevant to hypertext systems: not knowing where to go next, not knowing how one arrived at a particular node, not knowing where the information is, and finally not knowing how to get there (Edward & Hardman, 1989). On the other hand, cognitive overhead is defined as “the additional effort and concentration necessary to maintain several tasks or trails at one time” (Conklin, 1987, p. 40). Users have to perform many tasks simultaneously, such as remembering tasks and sequences, searching target items, browsing general topics and related items, surfing items of interest, comparing between items, moving from one item to others, and so on. Performing all these tasks simultaneously causes users to experience cognitive overload, which may lead them to get lost in hyperspace (Kim & Hirtle, 1995). A plausible reason for these problems is the lack of context information in Web systems. Context information is defined as the explanation of users’ current situation in the Web environment. The context information is important for effective navigation because each navigation process takes place in a particular information environment and is inextricably tied to the specificity of the environment (Jul & Furnas, 1997). If users do not have appropriate context information, they could experience disorientation, because context information provides the temporal and structural cues of locations. At the same time, users without context information tend to experience cognitive overload induced by cognitive overhead, because context information also provides valuable cues for users’ actions and task flows. Users frequently experience cognitive overload and disorientation in Web systems because the WWW is based on hypertext, the nonlinearity of which hinders users from maintaining the context information. Hypertext systems have the ability to produce complex, richly interconnected, and cross-referenced bodies of various information (Fillion & Boyle, 1991). However, at the same time, hypertext can also produce complicated and disorganized tangles of haphazardly connected Web sites, which do not provide users with appropriate context information (Utting & Yankelovich, 1989). Although several previous studies have been conducted to design effective hypertext systems (Furnas, 1997; Glenn & Chignell, 1992; Jul & Furnas, 1997), there has been little research on the relation between Web systems and context information, in spite of the importance of context in hypertext systems. In this study, we devised a simple method to provide two types of contextual navigation aids by changing the link properties of Web systems. We then evaluated their effectiveness empirically on two different task types in two different Web systems. The objective of this study was to investigate empirically the impact of context information on various tasks in diverse Web sites, and thereby to provide a basis for the design of an effective navigation aid that could be applied to a wide variety of situations.

Contextual Navigation Aids

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2. CONTEXT Context refers to the information surrounding stimuli being recognized, categorized, or searched for. Therefore, the context can provide feedback that tells the user where he or she is in the process, what the past choices and outcomes were, and possibly how much further it is to the terminal node (Norman, 1991). As explained in Section 1, context information is more important on the Web than in other applications, because the WWW has various open structures and various types of goal. In particular, context information is extremely important in the navigation process, where the user experiences disorientation and cognitive overload because each navigation process on the Web takes place in a particular information environment of temporal-spatial context (Utting & Yankelovich, 1989). First, disorientation can occur when users fail to compute the temporal-spatial contextual coordinates of the current information. Therefore, disoriented users need context information to reestablish a sense of location. Context information that provides the structure of the document, size of the document, and the way the document responds to given functions may help users reestablish their sense of location (Fillion & Boyle, 1991). Especially when information is scattered across wide areas of Web sites, context information may help users to orient their locations more effectively. Second, cognitive overhead can occur when users fail to remember their actions and task flows. Therefore, users under cognitive overhead need context information to identify the location and to understand current task flows at any time in any place within hyperspace. Context information is especially important for Web systems, because delays inherent in Web navigation add to the user’s cognitive load, because the user has to keep contextual information in mind while waiting (Shubin & Meehan, 1997). In particular, two types of context information are needed: spatial context and temporal context. First, spatial context is related to the question “Where can I go from here?” (Utting & Yankelovich, 1989). Several alternative ways can be used to answer this question. In this study, the structural context is provided to give a preview extended from the current position to all other positions that can be reached within two clicks. The structural context is expected to facilitate forward navigation, that is, making predictions of what will come next (Perrig & Kintsch, 1982; Pohl, 1982). By showing the structural context information, we expected users to reestablish orientation and identify the location of the target item more easily. Second, temporal context is related to the question “How did I get here?” (Utting & Yankelovich, 1989). To answer this question, we provide the temporal context that contains all the distinctive locations that users have visited until the current time. Therefore, the temporal context can facilitate backward navigation by facilitating the search for previously encountered information. By showing the temporal context, we expected users to remember less about their past trails and perceive the task flow at the current time and location more easily.

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3. TYPES OF TASKS Nowadays, Web systems play important roles in performing various types of tasks. For example, users can use the WWW to search for a specific item or to acquire general information about interesting topics (Chen, Wang, Proctor, & Salvendy, 1997). These different types of tasks have been found to make Web users employ different navigation strategies (Carmel et al., 1992), which may consequently affect the effectiveness of the contextual navigation aids proposed in this study. The various tasks performed in Web systems can be classified into two major types (Chen et al., 1997). First, users conduct a search task to acquire specific items. In searching tasks, users have a particular, known, specific objective for which a specific answer can be sought directly (Cove & Walsh, 1988; Marchionini, 1989). Second, users explore Web systems to get information about a broad range of interesting topics. In browsing tasks, users have a general objective, led by curiosity and desire, and they try to obtain open-ended and exploratory information about the objective (Neilsen, 1990). This study included both the searching and browsing tasks to investigate the impact of task types on the effectiveness of contextual navigation aids. We expected the contextual aids to be helpful for both the search and browsing tasks, because both tasks require users to have accurate information about their current location, as well as prior and future locations, which can be effectively provided by the contextual navigation aids.

4. CONTEXTUAL NAVIGATION AIDS Various contextual navigation aids have been developed to solve the severe problems in using hypertext systems (Utting & Yankelovich, 1989). The navigation aids can be classified into two categories: one with a global scope and the other with a local scope. The first category of navigation aids includes overviews of the node structure of an entire Web system. A comprehensive overview can help users understand the entire system structure. However, as the size of Web systems increases radically, providing the entire structure of Web systems in a single page becomes extremely difficult, if not impossible. Therefore, we need the second category of navigation aids that provide only the local navigation for Web systems. In this study, we provide the local navigation aids by developing two types of add-on links in the navigation design. The navigation design is to develop a link structure through which users can move from one page to another with minimal effort. Links are generally categorized as either basic or add-on links. Basic links are a set of minimal connections that enable users to visit any node in a Web system. Basic links are mostly predetermined by the system’s node structure. On the other hand, add-on links are additionally provided to improve the navigation behavior. These add-on links are particularly useful when the basic links do not facilitate effective navigation by themselves (Furnas, 1997). However, too many add-on links will not only confuse users’ logical understanding of information (Morris & Hinrichs, 1996) but also will lead the users to unexpected destinations in the site (Edward & Hardman,


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1989). Moreover, if add-on links are not properly presented within the site, users may experience disorientation and cognitive overload (Lynch & Horton, 1997). In this study, we provide two types of contextual navigation aids (structural and temporal) by using two sets of add-on links on top of the basic links within a hierarchical structure. The hierarchical structure is assumed in this study because it has been used widely by most large-scale Web sites (Morris & Hinrichs, 1996). Two basic links are provided in all conditions: up-to-parent links (UTP) and down-to-child links (DTC). These links allow participants to move one level up or down along the hierarchy from the current position (CP). The basic and add-on links provided in this study are shown in Figure 1. To provide structural context, we developed three kinds of add-on links: next-to-peer links (NTP), up-to-grandparent links (UTG), and down-to-grandchild links (DTG). We expected that all the links for the structural context would have two functions: to jump between distant locations and to preview the local context information. First, NTP links support horizontal navigation among peer levels in the hierarchical structure. When a participant is viewing one page, he or she can move directly to an adjacent page within the same level using NTP links. UTG links help participants at a certain level to move two levels directly upward, and DTG links help participants to move two levels directly downward. Therefore, these links enable users to jump to distant locations directly without stopping at the intermediate level. Second, the set of all these links (NTP, UTG, and DTG) provides structural context by previewing all the nodes that are two levels upward, two levels downward, and at the same level as the current location. Consequently, the combination of the three additional links and two basic links can provide contextual information about the local structure around the current location.

FIGURE 1

Display layout of context information.

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At the same time, to provide temporal context, we implemented a historical information mechanism, which we call the PATH links. The PATH link used in this study is a type of recency-based history that saves the Uniform Resource Locator (URL) only in its latest position (Tauscher & Greenberg, 1997). Recency is a simple yet effective temporal navigation aid, especially when duplicates are saved only in their latest position (Greenberg, 1993). Similar to the links for the structural context, PATH links providing for the temporal context would have two functions: to jump to the distant nodes visited before and to review the local context information. First, the PATH links enable users to move to distant nodes that they have visited in the past without stopping at the intermediate locations. Second, the PATH links maintain the local context, because URLs that have been visited recently will stay at the top of the list (Greenberg, 1993).

5. OVERVIEW OF STUDY The aim of this study was to empirically examine the effects of two types of context information, structural and temporal context. We evaluated the effectiveness of contextual navigation aids for two types of tasks (searching and browsing) within two different domains. First, two domains were selected that were radically different from each other along a dimension that is supposed to influence the effectiveness of contextual navigation aids. We decided that the degree of structuredness is an important dimension, because different degrees of structuredness can affect navigation patterns (Smith, Newman, & Parks, 1997). Two extreme cases were selected along the degree of structuredness. One extreme is a well-defined structure, and the other extreme is an ill-defined structure. The well-defined structure has a simple and balanced category structure that has the same number of levels across all branches. The advantage of well-structured hierarchies is that users can expect the category of alternatives at each level and predict the local category of the system in any node (Norman, 1991). On the other hand, an ill-defined structure has a complex, unbalanced category structure owing to the asymmetric nature of categories and subcategories. The number of alternatives varies throughout the structure, and the length of paths to terminal nodes is not necessarily constant (Norman, 1991). Therefore, the ill-defined structure gives users more difficulty in predicting subcategories and terminal nodes compared to the well-defined structure. Second, a good representative domain was chosen for each type of the two structures: an electronic commerce (e-commerce) system and a content dissemination system. In general, an e-commerce system has a well-defined structure because of its well-categorized physical products and relatively stable category sizes. On the other hand, a content dissemination site usually has an ill-defined structure because relevant information for subcategories is expanding almost randomly as time goes by. Therefore, even if a content dissemination site starts with a good balanced structure, the entire structure tends to become unbalanced in a short time. Third, searching and browsing tasks were designed that may be typical of each domain. For example, in an e-commerce system, a searching task asked partici-


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pants to buy a specific brand of traditional wines, and a browsing task required participants to look for birthday presents for their significant others. On the other hand, in a content dissemination system, a searching task required participants to identify specific information about specific government agencies, and a browsing task asked participants to investigate the pros and cons of studying abroad. A set of two experiments was conducted to test the effects of context information in two types of tasks, searching and browsing, at each domain. First, the effects of the context information on searching and browsing were examined in the e-commerce system. Second, the effects of the context information were examined in the content dissemination system. We hypothesized that context information would be useful in both the e-commerce system and the content dissemination system. The two types of context information were also expected to be useful both for the searching and browsing tasks.

6. EXPERIMENT 1: E-COMMERCE SYSTEM 6.1. Method Participants. Forty undergraduate students at Yonsei University participated in the experiment. The participants were randomly divided into four groups: control group, structural context only group, temporal context only group, and both structural and temporal context group. Ten participants were assigned to each group, and they were tested individually in the experiment.

Design. A mixed design was used. The structural context (provided, not provided) and temporal context (provided, not provided) were manipulated between participants, and task type (searching task, browsing task) was manipulated within participants. The dependent variables were the total number of nodes visited, the number of nodes visited repeatedly, and the subjective ratings for navigation convenience.

Materials. A prototype of the well-structured e-commerce system used in the experiment was called “Cyber Shopping Mall.” This prototype was a hypertext document with a well-balanced hierarchical structure consisting of five levels similar to common Internet shopping malls. With the owner’s consent, this prototype was constructed based on a cyber shopping mall that had actually been conducting business for several months. This entire mall consisted of seven departments, 18 stores, 66 corners, and 674 products in total. The experimental mall was constructed in four versions, as shown in Figure 2. All were identical in terms of the content and graphical layout, differing only in terms of contextual navigation aids. Normal history mechanisms in the browser were disabled to investigate the exact effects of each context information. Participants with both context information aids actually saw links on the content pages as

FIGURE 2 200

(Continued)

FIGURE 2 Actual user interface in the electronic commerce system: actual interface with both structural context and temporal context (p. 202 top), actual interface with the structural context only (p. 202 bottom), actual interface with the temporal context only (p. 203 top), and actual interface without the context information (p. 203 bottom). 201

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shown in Figure 1. In the control group, participants saw only two basic links (UTC, DTC). In the temporal context only group, participants saw the PATH links in addition to the two basic links. Finally, in the structural context only group, participants saw five links in total: UTG, DTG, and NTP links in addition to the two basic links. Microsoft Internet Explorer 4.0 was used in the experiment, and experimental sites were on a local server; therefore, the waiting times for pages to load were usually very short and consistent.

Procedure. The experimental sessions were divided into three sections. First, participants were given instructions about the general nature of the experiment and were allowed to practice using all links that would be provided in the experiment. Next, participants were required to fill out a prequestionnaire that asked them if they had any prior experience using computers as well as the WWW. Participants then used 7-point scales to rate the self-perception of their ability to navigate the WWW, which ranged from 1 (strongly disagree) to 7 (strongly agree). The questions from the prequestionnaire are presented in Table 1. After the prequestionnaire, four searching tasks and three browsing tasks were provided in a random order. Participants were asked to perform the given tasks one by one within 10 min per task. Examples of each task type are as follows: • Searching task: You are getting a gift for your teacher. Order a traditional wine, either Moonbae-wine or Leegang-wine. • Browsing task: Order a birthday gift for your girlfriend or boyfriend. The navigation behaviors of each participant were recorded in system log files. After performing each task, participants were asked to answer a postquestionnaire. The postquestionnaire consisted of three questions to measure the ease of navigaTable 1: Questions of Prequestionnaire Prequestionnaire

Question

General questions of previous experience

How long have you used computers for work? How often have you used computers for work? How long have you used the WWW? How often have you used the WWW? Have you ever visited cyber shopping malls (or studying abroad sites) on the Internet? I am skilled at using the WWW. I usually find target information easily. I have experienced disorientation in navigating the WWW frequently. I know many methods to navigate the WWW. I am skilled at using search engines and downloading programs.

Degree of skill for using the WWW Ease of information retrieval Past experience of disorientation Prior knowledge of navigation methods Use of navigation tools Note.

WWW = World Wide Web.


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tion, the ease of locating the items, and the ease of comparing multiple items. Under each item a 7-point scale was presented, ranging from 1 (strongly disagree) to 7 (strongly agree). Questions of the postquestionnaire are presented in Table 2. The analysis was performed for each of the three experimental sections. First, the prequestionnaires were analyzed to investigate the differences among the experimental groups in terms of their ability to navigate the WWW. Second, three kinds of data were analyzed using the system log files: usage of the context information, number of nodes visited, and number of nodes repeatedly visited. The number of times participants used the contextual aids was first analyzed for the manipulation check. Next, we measured the total number of nodes visited and the number of nodes repeatedly visited, because disorientation and cognitive overhead can make participants miss out sections of the site and open specific nodes repeatedly. This leads to an increased number of visits to navigational pages, which in turn increases the total number of nodes visited. Finally, the postquestionnaires were analyzed to investigate the perceived navigation convenience.

6.2. Results Prequestionnaire result. To investigate the participants’ background in navigating the WWW, five questions in the prequestionnaire asked the degree of skill for using the WWW, the ease of information retrieval, the past experience of disorientation, prior knowledge of the navigation method, and the use of the navigation tool. An analysis of variance (ANOVA) was conducted with the participants’ responses to the prequestionnaire. As shown in Table 3, there was no difference among the four participant groups: the degree of skill for using the Internet, F(3, 36) = 0.65, ns; the ease of information retrieval, F(3, 36) = 0.21, ns; the past experience of disorientation, F(3, 36) = 0.60, ns; the prior knowledge of navigation method, F(3, 36) = 0.33, ns; and the use of navigation tool, F(3, 36) = 0.63, ns. These results indicate that the previous individual experience of the Web did not affect the difference among the four groups induced by providing context information.

Use of the context aids. Table 4 presents the mean use rate of the context aids. We measured the frequency of each link usage in the log data. The mean rate of use has been computed as: (the number of each link to move ÷ the total number of links to move) × 100. The mean rate of using structural context links (UTG, DTG, and NTP links) is 77%, and the mean rate of using temporal context links (PATH links) is 16%. The results indicate that most participants were aware of the given contextual aids and used them throughout the experimental sessions.

Total number of nodes visited. Figure 3 shows the mean number of nodes visited per task during experimental sessions for all four groups. ANOVA results revealed main effects of structural context, F(1, 36) = 34.82, p < .001, and temporal

Table 2: Questions of Postquestionnaire Question No.

Questions of Navigation Convenience

1 2 3

Was it easy to locate the target item that you wanted to get in this site? Was it easy to navigate around this site? Was it easy to compare multiple products (information) in this site?

Table 3: Mean of Prequestionnaire in the Electronic Commerce System Temporal Contexta

a

Control

Structural Contexta

Botha

Category

M

SD

M

SD

M

SD

M

SD

Skill for using the Internet Ease of information retrieval Past experience of disorientation Prior knowledge of navigation methods Use of navigation tools

3.2 3.1

1.8 1.7

2.4 2.7

1.4 1.6

2.1 2.5

1.5 1.5

2.6 2.7

2.3 2.0

5.2

1.6

4.1

2.1

5.2

2.2

4.9

2.3

3.1 3.3

1.3 1.7

2.5 3.1

1.9 1.9

2.5 2.5

1.0 2.1

2.5 2.1

2.0 2.7

a

n = 10. Table 4: Mean Use Rate of the Context Aids in the Electronic Commerce System

Link Type UTP DTC UTG DTG NTP PATH

Control

a

Temporal Contexta

Structural Contexta

Botha

36 64 — — — —

16 67 — — — 17

10 10 13 40 27 —

2 11 8 40 25 14

Note. Mean use rate is expressed as percentage. UTP = up-to-parent; DTC = down-to-child; UTG = up-to-grandparent; DTG = down-to-grandchild; NTP = next-to-peer; PATH = historical information mechanism. a n = 10.

FIGURE 3 Number of nodes visited in the electronic commerce system during the searching task (left) and browsing task (right). 204


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context, F(1, 36) = 10.93, p < .005. However, there was no significant difference between the two task types, F(1, 36) = 0.12, ns. Thus, regardless of task type, participants visited significantly fewer nodes with the structural context than with the nonstructural context (8.1 pages vs. 14.9 pages). Also, when participants were searching or browsing with the temporal context, they visited fewer nodes than did the nontemporal context group (9.4 pages vs. 13.3 pages). There was also a significant interaction between the structural context and the temporal context, F(1, 36) = 5.93, p < .05. When the structural context was provided, there was little difference between participants with the temporal context and those without the temporal context (7.6 pages vs. 8.6 pages). However, when the structural context was not provided, there was a considerable difference between participants with the temporal context and those without the temporal context (11.5 pages vs. 18 pages). In other words, the temporal context was found to influence the navigation patterns only when the structural context was not provided.

Number of nodes repeatedly visited. Figure 4 presents the mean number of nodes repeatedly visited per task for all four groups. A between-subject and within-subjects ANOVA revealed main effects of structural context, F(1, 36) = 47.24, p < .001, and temporal context, F(1, 36) = 14.1, p < .005, showing that participants visited fewer repeated nodes with context information than those without context information regardless of task type, F(1, 36) = 1.31, ns. The structural and temporal context significantly reduced the number of repeatedly visited pages per task (3.9 pages by the structural context, 2.1 pages by the temporal context). There was also a significant interaction effect between the structural context and temporal context, F(1, 36) = 9.82, p < .005. When the structural context was provided, there was no difference between participants with the temporal context and those without the temporal context. However, if the structural context was not provided, there was a significant difference between participants with the temporal context and those without the temporal context. Therefore, the temporal context was found to play its roles only when the structural context was not provided.

FIGURE 4 Number of nodes repeatedly visited in the electronic commerce system during the searching task (left) and browsing task (right).

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Postquestionnaire result. Figure 5 shows the mean scores of three questions per condition for navigation convenience. The higher scores resulted in more convenient perceived navigation. ANOVA results revealed significant main effects of structural context, F(1, 36) = 5.03, p < .05, and temporal context, F(1, 36) = 9.30, p < .005. These results indicate that participants perceived the e-commerce system with the structural context as being more convenient for navigation than those without the structural context (5.2 vs. 4.6). Participants with the temporal context also reported finding it more convenient for navigation than did those without the temporal context (5.3 vs. 4.5). There was a significant interaction effect between task type and structural context, F(1, 36) = 8.91, p < .01, showing that the structural context had more influence on the convenience of navigation in the searching tasks as compared to the browsing tasks. When participants performed the browsing tasks, there was no significant difference between the structural context group and the nonstructural context group (5.1 vs. 4.8), as shown in Figure 6. However, in searching tasks, there was a significant difference between the structural context group

FIGURE 5 Subjective ratings for navigation convenience of the electronic commerce system during the searching task (left) and browsing task (right).

FIGURE 6 Interaction effect between the structural context and task type in navigation convenience of the electronic commerce system.


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and the nonstructural context group (5.2 vs. 4.5). Thus, the structural context was found to influence the convenience of navigation only in searching tasks.

7. EXPERIMENT 2: CONTENT DISSEMINATION SYSTEM 7.1. Method Participants. Sixty-four undergraduate students at Yonsei University participated in the experiment. The participants were randomly divided into four groups: control group, structural context only group, temporal context only group, and both structural and temporal context group. Sixteen participants were assigned to each group; participants were tested individually, as in the e-commerce system.

Design.

The experimental design was identical to that of Experiment 1.

Materials. A prototype of the unstructured content dissemination system used in the experiment was called “Studying Abroad Site.” We chose a specific domain for studying abroad among various domains, because participants participating in the experiment were undergraduate students who are familiar with studying abroad. This prototype was an unstructured hypertext document with an unbalanced hierarchical structure similar to common content dissemination systems. This prototype was constructed based on actual sites about studying abroad. This site consisted of nine levels of depth with 733 related nodes in total. The experimental site was constructed in four versions, as shown in Figure 7.

Procedure. All the experimental procedures, except specific tasks, were identical to those of the structured e-commerce system experiment. Participants were asked to perform two searching tasks and four browsing tasks. Examples of each task type are as follows: • Searching task: Find information on the difference between Kibbutz and Woof. • Browsing task: Select a foreign language course for language study. All the analysis procedures were identical to those of the structured e-commerce system experiment.

7.2. Results Prequestionnaire result. An ANOVA was conducted with the participants’ responses to the prequestionnaire.

FIGURE 7 208

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FIGURE 7 Actual user interface in the content dissemination system: actual interface with both structural context and temporal context (p. 210 top), actual interface with the structural context only (p. 210 bottom), actual interface with the temporal context only (p. 211 top), and actual interface without the context information (p. 211 bottom). 209

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As shown in Table 5, there was no significant difference among the four participant groups: the degree of skill for using the Internet, F(3, 60) = 0.21, ns; the ease of information retrieval, F(3, 60) = 0.38, ns; the past experience of disorientation, F(3, 60) = 0.87, ns; the prior knowledge of navigation method, F(3, 60) = 0.27, ns; and the use of navigation tools, F(3, 60) = 0.07, ns. These results indicate that the previous individual experience of the Web does not affect the difference among the four groups induced by providing context information.

Use of the context aids. Table 6 shows the mean use rate of the context aids. The mean rate of using structural context links (UTG, DTG, and NTP links) is 63%, and the mean rate of using temporal context links (PATH links) is 18%. Similar to the e-commerce case, the results indicate that most participants knew the given contextual aids and used them frequently during the experimental sessions.

Total number of nodes visited. Figure 8 presents the mean number of nodes visited while conducting tasks for all four groups. An ANOVA revealed main efTable 5: Mean of Prequestionnaire in the Content Dissemination System a

Control

Temporal Contexta

Structural Contexta

Botha

Category

M

SD

M

SD

M

SD

M

SD

Skill for using the Internet Ease of information retrieval Past experience of disorientation Prior knowledge of navigation methods Use of navigation tool

4.7

1.6

4.4

2.2

4.6

1.7

4.3

1.7

4.7

1.8

4.4

2.3

4.5

1.7

4.0

1.6

7.2

0.9

6.9

1.5

6.5

1.5

7.0

0.9

4.4 4.8

1.7 2.1

3.9 4.7

1.9 2.5

4.3 4.5

1.7 2.4

4.3 4.9

1.6 2.3

a

n = 16. Table 6: Mean Use Rate of the Context Aids in the Content Dissemination System

Link Type UTP DTC UTG DTG NTP PATH

Control

a

Temporal Contexta

Structural Contexta

Botha

29 71 — — — —

10 70 — — — 20

18 17 16 21 28 —

6 18 8 28 24 16

Note. Mean use rate is expressed as percentage. UTP = up-to-parent; DTC = down-to-child; UTG = up-to-grandparent; DTG = down-to-grandchild; NTP = next-to-peer; PATH = historical information mechanism. a n = 16.


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FIGURE 8 Number of nodes visited in the content dissemination system during the searching task (left) and browsing task (right).

fects of structural context, F(1, 60) = 60.65, p < .001; temporal context, F(1, 60) = 5.61, p < .05; and task type, F(1, 60) = 11.69, p < .005. Participants visited significantly fewer nodes with the structural context than with the nonstructural context (22.7 pages vs. 36.5 pages). Also, when participants were searching or browsing with the temporal context, they visited fewer nodes than the nontemporal context group (27.5 pages vs. 31.7 pages). Participants visited significantly more nodes in the searching tasks as compared to the browsing tasks (31 pages by searching vs. 28.2 pages by browsing). Moreover, there was a significant interaction effect between structural context and task type, F(1, 60) = 23.31, p < .001, as shown in Figure 9. The structural context played a more significant role when participants were performing search tasks (structural, 22.1 pages; nonstructural, 40 pages) than when performing browsing tasks (structural, 23.3 pages; nonstructural, 33.1 pages). There was no interaction effect between the structural context and temporal context, F(1, 60) = 1.21, ns.

Number of nodes repeatedly visited. Figure 10 presents the number of nodes repeatedly visited for all four conditions. An ANOVA showed main effects of structural context, F(1, 60) = 31.03, p < .001; temporal context, F(1, 60) = 8.55, p < .01; and task type, F(1, 60) = 13.57, p < .001. The main effect of the context information revealed that participants with the context information visited fewer repeated nodes than did those without the context information. These results indicate that the structural and temporal context significantly decreased the number of repeatedly visited pages (27 pages by the structural context, 15 pages by the temporal context). Also, the main effect of the task type showed that participants revisited more nodes in searching tasks than in browsing tasks (11.8 pages vs. 9.9 pages). Moreover, there was a significant interaction effect between the structural context and task type, F(1, 60) = 4.95, p < .05, showing that the structural context played a more important role in the searching tasks (structural, 8.7 pages; nonstructural, 14.8 pages) as compared to the browsing tasks (structural, 8 pages; nonstructural, 11.9 pages), as shown in

FIGURE 9 Interaction effect between the structural context and task type for the number of nodes visited in the content dissemination system.

FIGURE 10 Number of nodes repeatedly visited in the content dissemination system during the searching task (left) and browsing task (right).

FIGURE 11 Interaction effect between the structural context and task type for the number of nodes repeatedly visited in the content dissemination system. 212


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Figure 11. There was no significant interaction effect between the structural context and temporal context, F(1, 60) = 0.02, ns.

Postquestionnaire result. Figure 12 shows the mean scores of three questions per condition for the navigation convenience. An ANOVA revealed significant main effects of structural context, F(1, 60) = 12.68, p < .005; temporal context, F(1, 60) = 15.46, p < .001; and task type, F(1, 60) = 13.94, p < .001. The content dissemination system with the structural context was easier to use in navigating than that without the structural context (4.2 vs. 3.5). Also, participants with the temporal context reported that it was more convenient for navigation than participants without the temporal context reported (4.2 vs. 3.4). Moreover, there was a significant interaction effect between the structural context and task type, F(1, 60) = 13.94, p < .001. The structural context played a more important role in searching tasks (structural, 4.2; nonstructural, 3) as compared to the browsing tasks (structural, 4.2; nonstructural, 3.8), as shown in Figure 13. There was no significant interaction effect between the structural context and temporal context, F(1, 60) = 0.83, ns.

FIGURE 12 Subjective ratings for navigation convenience of the content dissemination system during the searching task (left) and browsing task (right).

FIGURE 13 Interaction effect between the structural context and task type for navigation convenience of the content dissemination system.

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8. CONCLUSION AND DISCUSSION In summary, participants perceived the Web system with the context information as being more convenient for navigation than those without the context information. Participants with the context information visited fewer nodes repeatedly, and they therefore visited fewer pages in total. Moreover, these benefits were observed across two different types of Web systems and two different types of tasks. These results indicate that the contextual navigation aids play a powerful role regardless of domain and task characteristics. Therefore, even though different Web systems or different tasks may induce various navigation patterns, the context information turned out to be equally useful. The structural context could help participants to reduce navigation problems by previewing information, and the temporal context may contribute to reducing the navigation problems by reviewing information. Even though the two systems were similar in terms of the effects of contextual aids on navigation behaviors, a couple of differences were observed between the e-commerce and the content dissemination systems. For example, a strong interaction effect between the structural and the temporal context was observed based on the results of the total number of nodes visited and repeatedly visited in the e-commerce system but not in the content dissemination system. In other words, the temporal context affected the participants’ navigation patterns in the content dissemination system even though the structural context was provided simultaneously. On the contrary, in the e-commerce system, the temporal context played a role in reducing the intermediate pages only when the structural context was not provided. This difference can be explained in terms of the category structure in the two domains. According to the data from the observed users’ behavior during the experiment session in the e-commerce system, on the whole, participants had a tendency to move through the temporal context links (PATH links) to jump to the main menu directly and to compare products previously visited. However, participants who had been provided with both temporal and structural context together tended to move by UTG links to the main menu and tended to move by NTP links for comparing several products visited instead of PATH links. In the case of the e-commerce system, most items were easily classifiable into the appropriate categories because of the simple category structure, which usually made it possible to locate relevant information within two clicks from the target. Therefore, most of the related information could be provided by the structural context alone in the e-commerce system. On the other hand, in the case of the content dissemination system, participants provided with both the temporal and structural context together had a tendency to move by UTG links to the main menu in place of PATH links. However, contrary to the e-commerce system, participants tended to move by PATH links to compare information previously visited. In other words, most tasks and relevant information in the content dissemination system were dispersed across wide areas further than two clicks away. Therefore, the structural context could not provide most of the needed information alone, and the temporal context could still play a role even with the structural context. Likewise, even though the contextual aids turned out to be effective for both the searching and browsing tasks, a couple of differences were identified in terms of


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different types of tasks. For example, there was a strong interaction effect only between the task type and the structural context, not between the task type and the temporal context. In other words, the temporal context information helps participants to the same degree both in terms of searching for specific items and browsing for general ideas. On the other hand, even though the structural navigation aids facilitate both the searching and browsing tasks, they play a more powerful role for the searching task than for the browsing task. This may happen because the target items for the searching task are specific enough that they can usually be located within two clicks from the source. On the other hand, the target items for the browsing tasks are usually dispersed across wide-open areas, and therefore the structural aids may not be able to help participants for the browsing tasks as much as for the searching tasks. The browsing task may need more review than the searching task, because participants already know the specific item to find in searching tasks. Therefore, their search scope is narrower than in the browsing tasks. There are several limitations to this study. First, even though this study conducted experiments with two different systems, it could not compare the two systems directly because the two domains are different both in terms of the level of structuredness and in the domain characteristics of tasks. These different domains make us unable to discern whether the node structuredness or the task domain characteristics influenced the differences between the two groups. Therefore, to investigate the effects of structuredness and task domain characteristics on the contextual information, further studies should conduct more controlled experiments using homogeneous domains and similar tasks. Second, we tested only one type of structure, the hierarchical structure. We selected the hierarchical structure because it is one of the most widely used structures in the current Web systems. However, other types of structures may result in different effects of context information. Future studies should include other types of structures, such as linear, grid, and network structures. Third, the tasks in this study include searching specific items and browsing general topics. However, other types of tasks, such as informational tasks and navigational tasks, may be influenced differently by the contextual navigation aids. Future studies should be extended to include other types of tasks and should analyze the effects of context information in terms of various features of tasks. Fourth, in our experiments, participants were asked to perform given tasks one by one within a given time limit of 10 min per item. This time limit was determined according to the results of the pretest, in which users had been tired from navigating after 10 min per item. Because of the complexity of task and system, users usually worked on one task for the full 10 min, and therefore we did not need to measure task performance time in our experiment. However, future studies should address the time issue to acquire navigation patterns in a more natural situation. Fifth, the presentation of additional navigation material (i.e., contextual navigation aids) may take resources away from the users. In this study, in spite of these costs, users with additional links reduced their repeated pages and total visited pages. Therefore, there seem to be some trade-offs between the additional costs and

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the benefit of contextual links. The context information could make users see many items to move at one time. This benefit seems to be high enough to outweigh the additional costs, such as time spent and screen space. The accurate trade- off between the costs and the benefits cannot be measured and cannot be predicted in this study. Sixth, the selection of domain and task were based on our intuition. There were no accurate metrics for various Web systems and for the tasks of each domain that we have used in our study. In future studies, the selection of domain and task should be based on accurate and objective criteria reflecting natural environments. Seventh, the participant population consisted of mostly undergraduates in Korea, and therefore the results may bring about different consequences in other participant populations. Future studies should be extended to include various populations to increase external validity. In conclusion, the impact of contextual navigation aids is substantial in enhancing the navigation patterns and consequently decreasing the problems of disorientation and cognitive overhead. This effect is meaningful because it can be observed across two radically different domains and two different types of tasks. Moreover, the study results can be more substantial because our method of providing the contextual aids is by simply changing the add-on links. Therefore, wide use of the contextual navigation aids suggested in this study is expected to solve recurrent navigation problems and increase the overall usability of most Web systems.

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