Concept maps and mind maps have long been used as teaching tools. Now, innovative Web-based technologies like http://www.SpicyNodes.org have made these tools available to on-line exhibit designers. On-line concept maps facilitate teaching complex and multifaceted topics while offering a visually rich and interactive interface that fuels visitors’ curiosity. These concept maps provide a novel way to convey information and integrate interactivity into on-line exhibits. This paper outlines the rationale and operation of concept maps, describes the author’s SpicyNodes system, and provides three examples of integrating SpicyNodes into on-line exhibits from the WebExhibits museum.
The Institute for Dynamic Educational Advancement (IDEA), a nonprofit organization, demonstrated SpicyNodes at the Museums and the Web 2010 conference (MW2010). SpicyNodes is a Web-based concept mapping tool that can enhance on-line exhibits and help to reach graphical and kinesthetic learners. It has free versions for the public, paid versions for organizations and enterprises at an affordable cost, and a multi-touch tablet version in development.
IDEA develops and curates http://www.WebExhibits.org, an interactive, on-line museum of science, humanities, and culture. Launched in 1999, WebExhibits was one of the first on-line museums, and currently hosts nine major exhibits on topics ranging from “Poetry through the Ages” to “Daylight Saving Time” to “Color Vision & Art” (Douma, 2000). Whether visitors are looking for a quick answer to a specific question or want to delve deeply into a topic, the exhibits’ information, virtual experiments, and hands-on activities prompt them to think, formulate questions, and explore topics from a variety of angles. We have found SpicyNodes to be an invaluable addition to these exhibits.
Concept maps have been briefly discussed several times at prior MW and ICHIM conferences.
At MW2003, Cameron reported on her interviews with curators, educators, and members of the public in Sydney and New Zealand about their motivations with respect to on-line collections. The curators expressed strong interest in providing information in forms that suited the conceptual understandings of a range of users, including timelines, information hierarchies, and concept maps. The curators noted the importance of repackaging information to suit the specific needs of different subsets of the audience, as well as providing options for users to tailor their experiences. Cameron also interviewed educators, who likewise felt that timelines and concept maps were good ways to visually connect objects, ideas, metaphors, and related themes, as well as to support a range of learning options. Moreover, they noted that graphically driven interfaces to search, browse, and contextualize collections were not only engaging and interactive experiences, but also served as a welcome departure from catalogued information. Many younger people she interviewed were also interested in spatial associative concepts such as concept maps with magazine style interfaces, visual prompts, and interactivity. Despite these findings, concept maps did not enjoy widespread use. The authors believe this failure to take hold was due to the technical complexity and cost of creating interactive, on-line concept maps from scratch.
The same year, at MW2003 and ICHIM03, Srinivasan examined representing material that museums collect, and its interactions with communities. He specifically looked at conceptual maps where the links between individual pieces of knowledge are delineated. These ontology representations organized and interrelated the stories of a community in a way that was responsive and faithful to the existing social fabric, and drew attention to the work of Joseph Novak and Albert Cañas in learner-created knowledge models. The style of concept maps promoted by Novak displays prepositions between nodes. Again, the limitation in 2003 was that there were concept map authoring systems for the desktop, but no adaptable displays for on-line use.
In 2007, at ICHIM07, Norio Togiya and Akira Baba presented a digital archive of historical photos by photographer Hikoma Ueno. They used “ontology maps” to allow users to select materials and understand the relationships between various items. These items are composed of the people, organizations, time, place, objects, and abstractions related to the materials. The relationship between these items is visualized as a chart, and the material can be selected. Their system was limited, however, because they had a very simple layout engine. While they advocate the use of ontologies, their evaluation found that, “It takes a long time to display the materials, and we often felt that the operation was heavy. As a result, the interface needs improvement” (Togiya & Baba 2007).
More recently, in a 2009 article, Cameron and Mengler wrote about hyper-complexity and transdisciplinarity in museums, and the inadequacy of collection documentation systems, which are overly limited in their cultural categorizations. The authors repeat the refrain about the value of concept maps, noting that, "Visual representations of Web information, like a wildly growing rhizome without a central root, offer a useful analogy for visually conceptualizing a complex documentation system, as an alternative cognitive map" (Cameron & Mengler 2009).
Our global team of engineers, designers, writers, and artists began working on SpicyNodes in 2005, as part of a research project into how the human mind naturally seeks information and how that could be translated to the on-line environment (Douma, et. al., 2009a, 2009b). We saw great promise in radial maps, which have been around for a century, and which were explored in earnest in the 1990s by several computer science researchers. When displayed on the computer, a key improvement is that layouts can be generated automatically, allowing a user to browse from node to node. Our team realized that radial maps could help users navigate many kinds of information, and that we could make an intuitive and natural tool that is easy to use and aesthetically pleasing, and fills current voids in how people find information (Douma, et. al., 2009c). We improved on the technology, developing the SpicyNodes engine that can present complex information in a way that invites exploration and triggers creative thought (Douma, et. al., 2008).
Other concept mapping and mind mapping tools include Comapping, Mindmeister, Mindmanager, bubbl.us, and CmapTools. A key difference is that these mind mapping tools have fixed layouts and orientations that do not automatically change as visitors move around. This puts a practical limit on the number of nodes. For example, CmapTools cannot display more than 30 nodes without becoming confusing and cumbersome (Briggs, 2004). For developers, the programming toolkit Prefuse Flare provides a flash-based layout engine for creating various types of tree layouts. Flare does not have specific multimedia or formatting features.
A useful ingredient in on-line exhibits
We advocate more Web-based exhibits, and describing the value of on-line concept maps is part of our broader interest in promoting more useful on-line exhibits. On-line exhibits can provide an authoritative, accessible, and fascinating resource that's also a cost-effective way of reaching large numbers of people around the world. With content selected, written, and guided by expert contributors and curators with a deep understanding of a subject, exhibits can tackle complex topics and make comprehensive efforts to cover the breadth of a topic while appealing to many audiences. As in a physical museum, exhibits present a perspective that's a step back from headline-driven news and fast-paced television shows. While there is widespread mistrust of the media, on-line exhibits leverage the trust and respect that the public has for museums. However, unlike a physical museum, an on-line exhibit is radically cost-effective. For example, over the course of ten years at WebExhibits, a single exhibit will likely reach 5 million visitors at an average cost of a few cents per visitor – a fraction of 1% of the cost associated with serving a visitor at a physical museum.
Concept maps are a useful component of on-line exhibits, as they help meet the needs of multiple learning styles and provide an innovative way to visualize information. We will include concept maps in all future exhibits we produce, and are retroactively adding them to older on-line exhibits. In addition, with emerging and future technologies, multi-touch concept maps can be used within an on-line exhibit, or as touch kiosks or mobile handhelds that can be carried within a physical museum.
3. Concept Maps Help (Some) Visitors Learn
By including concept maps like SpicyNodes, we help to meet the needs of multiple learning styles. For example, graphical learners can assimilate information by browsing images, maps, interactive timelines, appealing layouts, and concept maps. Auditory learners can be engaged by audio clips and audio guides. Read/write learners can respond to clear, lucid writing. Kinesthetic learners can be inspired by concrete examples, interactive figures, and descriptions of hands-on activities.
Matching how the mind stores ideas
Knowledge is stored in our brains as a network of interconnected concepts and propositions. When we learn something new, it’s crucial to integrate connections between new and existing concepts into our cognitive structure. Concept mapping has been studied extensively and has been shown to encourage meaningful learning, defined as representing a deeper understanding of materials (Novak, 1990). Educators consider concept hierarchy and cross-concept links the most important features of concept maps.
Established value of concept maps
From mapping the complex interdependencies of coastal ecosystems, to the web of love and betrayal in Shakespearian plays, concept maps are classroom workhorses that help students chart complex concepts. Through the process of creating and sharing these maps, students garner a depth and breadth of knowledge. As a result, maps provide students with a powerful and collective tool for taking notes in class, preparing for exams, and organizing and sharing complex research.
On-line mind mapping and concept mapping help the teaching and learning process. They can empower students to advance their own learning and to share their knowledge with their classmates and the public. Based on the constructivist model of learning, maps allow students to interrelate isolated concepts by visually representing and linking “nodes.” In addition, knowledge mapping helps students devise hypotheses more quickly in the learning process than do traditional text-based, threaded discussions (Suthers, et al, 2006).
There is extensive research demonstrating that concept mapping is a useful educational tool. The fields of medicine, nursing, science, and mathematics routinely utilize concept mapping as a constructivist approach in on-line learning environments (Concecao and Taylor, 2007). One study found that medical students learning physiology gained deeper meaningful knowledge and exhibited more critical thinking through the use of concept maps (Gonzalez et al., 2008). Concept maps have also been successful for public outreach about Mars exploration (Briggs, 2004).
Chiou (2008) found that concept mapping helped accounting students integrate and clarify complex materials in a much better way than did the use of textbook-style learning. Rueda et al. (2009) found that social science students could benefit and gain meaningful learning through the use of concept maps. These students were able to answer more questions correctly about the subject matter with concept maps than without. Similarly, Calderón-Steck (2006) engaged her social science students in an active exploration of race relations through the use of concept maps. She discovered that concept maps enhanced students’ critical thinking skills by visually connecting social, historical, and economic factors to ideas about race relations.
4. Information Visualization
SpicyNodes is a way to visualize on-line information that mimics the way people look for things in the real world. Bits of information – such as text, links, photos, and other media – are placed into "nodes," which are then linked together in an appealing interface that invites exploration. SpicyNodes turns complex information into a richly interactive content portal, and can help visitors explore on-line exhibits.
With an inviting interface, SpicyNodes nicely complements search engines or other methods of browsing. It can also grab data from collection management software via a simple XML interface. Exhibit visitors can adjust their focus, exposing more information (images, videos, text) in a node, or zoom out for a broader view. For example, visitors to a virtual art collection can drill down to Impressionists > Monet > Water Lilies with a few easy clicks. SpicyNodes has been successfully implemented in IDEA’s WebExhibits on-line museum.
SpicyNodes visualizes information typically organized in a hierarchical fashion. Starting from a broad topic defined in one node, progressively detailed information is nestled into descending generations of nodes. The top node of the hierarchy forms a nodemap root or home node. Its contents may describe the broadest perspective of a topic or may simply form a preface for different topics organized into a group of radially arranged descending branches. This kind of organization can map any type of menu-based or breadcrumbs-based navigation, but the applied layout introduces a better sense of relationships between pieces of information and allows easy forward or backward navigation. The radial layout also prevents visitors from losing their current perspective, a typical phenomenon in constantly reloading menu-based Web sites.
To escape hierarchy, SpicyNodes allows internal links between distant nodes. This creates connections between common content that occupies distant areas of a single, hierarchical nodemap. An example is a nodemap that organizes a painting exhibition and divides initial branches into separate eras and movements. At some point during navigation, after descending to the topic of Cubism, a visitor can encounter a well-known painting by Picasso with a clear reference to the 17th century art of Velázquez. With the inherent limitations of hierarchical organization, it would be hard to continue navigation toward this reference. A solution is an internal link node which, after being clicked, switches the context from Pablo Picasso to 17th century Spanish painting or directly to Velázquez.
Layout and optimization
In its implementation, SpicyNodes is based on existing standard approaches to the radial graph drawing introduced by Eades (1997), where a currently selected node forms the layout center and its descendants are radially arranged around it. Using a variety of techniques, our approach moves beyond previous research on smoothly animated radial graph layouts made by Pavlo, et al. (2006) and Yee, el al. (2001). Our extensions include support of invisible edges (internal links), rectangular text overlapping prevention, performance optimizations, and modification of nodes angular spreading. Text overlapping prevention is realized by staggering node distances, using an oval layout, and optimized force-directed algorithms (Quingley and Eades, 2000) applied to groups of nodes. Performance optimization is performed at various levels of application runtime. It consists primarily of geometry pre-calculations during idle time and of limiting the number of simultaneously visible nodes by using a subtree separation algorithm. The separation algorithm implements additional aesthetics that improve visual orientation in the scope of the currently visible context, such as using a constantly visible path to the home node and main topics. Angular spreading of child nodes favors equiangular distribution over the weight balance distribution that characterizes Yee's and Pavlo's layouts, which in our opinion deforms layouts for irregularly balanced trees.
SpicyNodes creates not only structurally solid but also graphically appealing layouts, so geometry calculations need to be complemented with a calculation of ornamental elements, including drawing various font styles, and using custom node and connector shapes, and other widgets. Therefore, extensions to previous research result in the creation of an application that draws and smoothly animates radial layouts consisting of a virtually unlimited number of nodes, while still being supported by modern personal computer processors.
SpicyNodes’ look and feel was developed with the input of 15 designers (see Acknowledgements for a list of designers) who created a number of skinning styles that could be applied over the visible geometry. Common to all styles are a visually distinguishable home node and all nodes forming paths between the current context and home. Distinctiveness is achieved with altered size, color, or fading, as compared to other groups of nodes. Aside from these rules, all styles vary in shapes, interaction effects, or content alignment, and range from minimalistic to visually complex. Additionally, styles may be mixed by applying a different style to nodes, their connectors, and the currently selected node, which creates a large number of possible combinations.
SpicyNodes’ draggable layout gives users a tangible feel for events by employing panning and rotation subsystems that simulate physical models of motion. Direction and speed of panning and rotation depend upon the direction of the cursor motion in relation to the center of mass of the layout.
To assist browsing and general navigation experience, various UI elements have been added, such as marking nodes that have been visited, marking parents, and an optional navigation panel that can include help, volume, zoom, focus, full screen, previous, next, home, and search bar.
A search engine supporting phonetic matching allows users to jump to a node if they know or suspect that it exists. SpicyNodes has a simple search engine with optional fuzzy matching that uses the “Double Metaphone” phonetic algorithm (Phillips, 2000) which supports non-English words like European and Asian names.
5. Three Real-Life Examples from WebExhibits
WebExhibits currently has three nodemap implementations, for the exhibits, “Daylight Saving Time,” “Calendars through the Ages,” and “Poetry through the Ages.” We will include concept maps in all future exhibits we produce, and are retroactively adding them to older on-line exhibits.
Statistics about visitor response
Like any feature of an on-line exhibit, concept maps like SpicyNodes are not intended to appeal to all visitors. The key value is to serve visitors (particularly visual and kinesthetic learners) who are currently ill served by other formats. We find that considerably more than half of our visitors like the on-line concept maps. For example, over the last year, in a brief, self-selected survey, in response to the question, “Do you like the nodes?”, 61% say “Yes,” 12% say “Maybe,” and 27% say “No” (2613 respondents). These ratios are relatively consistent among the three nodemaps in the exhibit. The authors anticipate that visitors who are ambivalent about the concept maps are under-reported.
6. Multi-Touch (Tablets, Handheld Devices, and Kiosks)
The on-line exhibit is moving towards single-purpose and handheld devices. Nodemaps spring to life when users can touch them. We plan to adapt SpicyNodes to work with emerging hardware and software accessories that support multi-touch and gestures. Written originally for the Adobe Flash platform, we are currently porting SpicyNodes to the Apple iPad (ObjectiveC) platform, which offers portability and advanced multi-touch and gestures support.
Multi-touch is a relatively young technology, but it is already supported by many types of hardware devices. These include mobile phones and other handheld devices, personal tablet computers, computer monitors, specially dedicated tools like Microsoft's Surface, and a vast number of experimental approaches that mix electronic and video-based motion detection to accomplish multi-touch and similar human interaction. The number of software platforms and frameworks supporting multi-touch devices has also grown. It includes new operating systems like Mac OS X, Windows 7, Ubuntu, Android, webOS, Xandros and development frameworks like Objective-C, Java (MT4j), Python (PyMT), and Air 2.0. Rapidly growing interest in multi-touch solutions indicates a new direction in applications interface design.
Among these devices, the Apple iPad offers extreme portability and a medium sized display (9.7”) with 1024x768 screen resolution, which is a good fit for full screen applications like SpicyNodes. Based on Objective-C, perhaps the most mature software platform in terms of supporting multi-touch technology, the iPad is equipped with a variety of wireless and cellular connectivity options. It is therefore a natural choice for implementing SpicyNodes’ radial layout interface, which provides natural and dynamic access to text and media content.
SpicyNodes is a good example of an application that could take tremendous advantage of multi-touch support. The SpicyNodes user interface provides controls such as scene zooming and focusing, dragging the whole layout, enlarging contents, and clicking displayed nodes to continue navigation. All these controls are good candidates for multi-touch gestures like touch pad clicking, pinching for scale change, and single or double touch rotation and panning.
7. How to Use SpicyNodes
Nodemaps can be integrated into any exhibit, providing a way to browse the exhibit contents, or to present many conceptual facets of a complex topic. Nodes can have any mixture of text, images, and videos. The nodes should be arranged from the visitor’s point of view, with appealing main branches. You can repeat nodes on different branches so that visitors have a few different routes to reach a node.
Notes about authoring
When authoring with nodemaps, principles of good communication apply. The following are a few general tips for authoring. More extensive guides, including tips for copywriters, are available on-line at http://www.spicynodes.org/cookbook-recipes.html.
- Synthesize the concepts. Meaningful learning goes deeper than definitions and rote memory work and into connections between ideas and knowledge (old and new).
- Keep in mind that you are working in two-dimensional space, and visitors don’t need to travel in a linear fashion from one nugget of information to the next. Provide a larger organization or hierarchy, within which your visitors follow their own paths.
- As part of mapping concepts, break down information into small bits of ideas.
- Keep it short and to the point. Optimally, the title length should be from one to six words; the text can range from a short phrase to several sentences, since visitors can read more information by expanding a node or by scrolling.
- Be interesting. Try to write node titles and descriptive text from your audience’s point of view. What would be familiar or interesting to your visitors?
- Make use of multimedia. You can add images and YouTube videos to your nodes. Plus, you can use HTML code, or color the node background and text color.
- Be user friendly. Add prompts as needed, such as “Check out this link for more information about the world’s largest geyser,” or “Click any node to get started.” Prompts are strongest when you start with a verb.
Be prepared for several weeks of work to author a large, useful nodemap. The magic of radial mapping systems like SpicyNodes is that the user is not overburdened with information. Rather, visitors focus on a center node, and see the context of the immediately connected nodes. If, for example, there are three levels of nodes, and each node is connected to five other nodes, there are 1 + 5 + 5^2 + 5^3 = 156, but the user only has to click 3 times to get to the end of a branch. This means that by design, it’s a lot of work to author a robust nodemap for an on-line exhibit. You might have well over 500 nodes, which can take several weeks to author. The technical step of loading the content into the nodemap takes only minutes.
SpicyNodes is an evolving application. We try to adapt its usability and development API to users’ expectations, based on their comments and case studies. The most recent version of SpicyNodes has three membership levels. One is completely free and used mainly by individuals, who can create an unlimited number of natural and aesthetic radial nodemaps consisting of virtually unlimited text and media content. Nodemaps can be created using a dedicated Flash based nodemap editor, or manually, by uploading an XML formatted file. The visual styles can be selected from a growing list of preset styles.
Organization and Enterprise members can use additional features, like a WYSIWIG style configurator, which allows detailed control over the visual style. In addition, they can create password-protected nodemaps and manage collaboration among of users. Enterprise users have access to SSL encryption.
IDEA offers limited scholarships to small nonprofits and research projects that wish to use the API but lack the financial resources. Interested developers can contact the authors to inquire about scholarships.
Extensive documentation for developers is available on-line from http://www.spicynodes.org/developers.html
One of the key advantages of on-line exhibits is the ability for visitors to access the exhibit “anywhere, anytime.” On-line concept maps like SpicyNodes help museums expand the range of methods used to convey knowledge to visitors, particularly those who are nonlinear, visual, or hands-on in their learning style. The authors are particularly excited about how the capabilities of interactive concept maps will further leap to life when delivered on the upcoming generation of multi-touch enabled devices.
The authors acknowledge the contributions of the whole SpicyNodes team, particularly including Sally Smith who edited the nodemaps, Sean Liu and Pavel Gritsai who have programmed the backend systems, and Ovidiu Ancuta, our lead user interface designer. We thank the following designers for their input on the user interface: Miguel Ángel Albadán, Tarek Atrissi, Simona Bucan, Patricia Carvalho, Michael Felix, Christophe Herbinet, Dusan Jelesijevic, Jonas Kühner, José López, Emanuel Mankert, Fabio Ernesto Mojica, Mikolaj Sadowski, Tristam Sparks, Steph Tekano, and Sait Yilmaz.
Briggs, G., D.A. Shamma, A.J.Cañas, R. Carff, J. Scargle and J. Novak. “Concept Maps Applied To Mars Exploration Public Outreach”. Concept Maps: Theory, Methodology, Technology. Proc. of the First Int. Conference on Concept Mapping . A. J. Cañas, J. D. Novak, F. M. González, Eds. Pamplona, Spain 2004.
Calderón-Steck, F.V. (2006). Concept mapping as a teaching/learning tool about race relations. Concept Maps: Theory, Methodology, Technology. Proc. of the Second Int. Conference on Concept Mapping. A. J. Cañas, J. D. Novak, Eds.
Cameron, Fiona, and Sarah Mengler (2009). "Complexity, Transdisciplinarity and Museum Collections Documentation: Emergent Metaphors for a Complex World". Journal of Material Culture 2009; 14; 189 DOI: 10.1177/1359183509103061
Cameron, Fiona (2003). "The Next Generation: 'Knowledge Environments' and Digital Collections". In J. Trant & D. Bearman (eds). Museums and the Web 2003: Proceedings. Archives & Museum Informatics, 2003. http://www.archimuse.com/mw2003/papers/cameron/cameron.html
Chiou, C-C. (2008). “The effect of concept mapping on students’ learning achievements and interest”s. Innovations in Education and Teaching International, 45, 375–387
Concecao, S. C. O., & L. Taylor (2007). “Using a constructivist approach with online concept maps: relationship between theory and nursing education”. Nursing education perspectives, 28, 268-275.
Douma, M. (2000). “Lessons learned from WebExhibits.org: Practical suggestions for good design”. In D. Bearman and J. Trant (eds.). Museums and the Web 2000: Proceedings. Archives & Museum Informatics, 2000. http://www.archimuse.com/mw2000/papers/douma/douma.html
Douma, M., I. Angelov & S. Menon. “Finding Information: Factors that Improve Online Experiences”. In Handbook of Research on Practices and Outcomes in E-Learning: Issues and Trends. Hershey PA: IGI Global. November 2009. (2009c) Also at: http://www.idea.org/find-information.html
Douma, M., G. Ligierko, O. Ancuta, P. Gritsai & S. Liu. “SpicyNodes: Radial Layout Authoring for the General Public”. InfoVis 2009, Atlantic City, New Jersey. (2009a)
Douma, M., & J. Romano. Creating online mind maps and concept maps .25th Annual Conference on Distance Teaching & Learning. August 4-7, 2009. Madison, Wisconsin. (2009b) http://www.uwex.edu/disted/conference/Resource_library/proceedings/09_20011.pdf
Douma, M., G. Ligierko & I. Angelov. “Promoting Creative Engagement with SpicyNodes.” Proceedings of the 34th Conference on Applications of Mathematics in Engineering and Economics (AMEE '08). AIP Conf. Proc., October 2008, Volume 1067, pp. 196-208.
Eades, P., R. F. Cohen & M. L. Huang. “Online Animated Graph Drawing for Web Navigation.” Graph Drawing 1997: 330-335
Gonzalez, H.L., A.P. Palencia, L.A. Umana, L. Galindo, & L.A.Villafrade (2008). “Mediated learning experience and concept maps: A pedagogical tool for achieving meaningful learning in medical physiology students”. Advanced Physiology Education, 32, 312-316.
Novak, J. D. (1990). “Concept maps and Vee diagrams: Two metacognitive tools for science and mathematics education”. Instructional Science, 19, 29-52.
Pavlo A, C. Homan & J. Schull. A parent-centered radial layout algorithm for interactive graph visualization and animation. 2006
Phillips, Lawrence. “The Double Metaphone Search Algorithm.” C/C++ User’s Journal, 18(6), June 2000
Quigley A, and P. Eades. “FADE: Graph Drawing, Clustering, and Visual Abstraction”. Proceedings of Graph Drawing 2000, Lecture Notes in Computer Science, Vol. 1984, pp. 183–196, Springer Verlag, 2000.
Rueda, U., A.Arruarte, J.A. Elorriaga, & E. Herran (2009). “Learning the attachment theory with the CM-ED Concept Map Editor”. Computers & Education, 52, 460-469.
Srinivasan, Ramesh (2003). "Village Voice: A methodology, interface, and evaluation of the collection of cultural heritage material.” ICHIM03.
Srinivasan, Ramesh. "Village Voice: An Information-Based Architecture for Community-Centered Exhibits". In D. Bearman and J. Trant (eds). Museums and the Web 2003: Proceedings. Archives & Museum Informatics, 2003.
Suthers, D.D., R. Vatrapu, R. Medina, S.Joseph, & N. Dwyer (2006). “Beyond threaded discussion: Representational guidance in asynchronous collaborative learning environments”. Computers & Education, 50, 1103–1127.
Togiya, N., and A. Baba. “Constructing an Integrated Digital Archive Using Ontology and the User Community”. In International Cultural Heritage Informatics Meeting (ICHIM07): Proceedings J. Trant and D. Bearman (eds). Toronto: Archives & Museum Informatics. 2007. Published October 24, 2007 at http://www.archimuse.com/ichim07/papers/togiya/togiya.html
Yee, K.-P, D. Fisher, R. Dhamija, & M. Hearst. “Animated Exploration of Dynamic Graphs with Radial Layout”. Proc. Information Visualization, 43-50, 2001.