Ontology visualization methods—a survey
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paper_title: Integrating Ontologies and Thesauri to Build RDF Schemas

paper_content:

In this paper we present a new approach for building RDF schemas by integrating existing ontologies and structured vocabularies (thesauri). We will present a simple mechanism based on the specification of inclusion relationships between thesaurus terms and ontology concepts and show how these relationships can be exploited to create application-specific RDF schemas incorporating the structural views of ontologies and deep classification schemes provided by thesauri.
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paper_title: Information Visualization Techniques in Bioinformatics during the Postgenomic Era.

paper_content:

Information visualization techniques, which take advantage of the bandwidth of human vision, are powerful tools for organizing and analyzing a large amount of data. In the postgenomic era, information visualization tools are indispensable for biomedical research. This paper aims to present an overview of current applications of information visualization techniques in bioinformatics for visualizing different types of biological data, such as from genomics, proteomics, expression profiling and structural studies. Finally, we discuss the challenges of information visualization in bioinformatics related to dealing with more complex biological information in the emerging fields of systems biology and systems medicine.
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paper_title: User Experiments with Tree Visualization Systems

paper_content:

This paper describes a comparative experiment with five well-known tree visualization systems, and Windows Explorer as a baseline system. Subjects performed tasks relating to the structure of a directory hierarchy, and to attributes of files and directories. Task completion times, correctness and user satisfaction were measured, and video recordings of subjects' interaction with the systems were made. Significant system and task type effects and an interaction between system and task type were found. Qualitative analyses of the video recordings were thereupon conducted to determine reasons for the observed differences, resulting in several findings and design recommendations as well as implications for future experiments with tree visualization systems
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paper_title: Graph Visualization and Navigation in Information Visualization: A Survey

paper_content:

This is a survey on graph visualization and navigation techniques, as used in information visualization. Graphs appear in numerous applications such as Web browsing, state-transition diagrams, and data structures. The ability to visualize and to navigate in these potentially large, abstract graphs is often a crucial part of an application. Information visualization has specific requirements, which means that this survey approaches the results of traditional graph drawing from a different perspective.
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paper_title: A Comparative Study of Four Ontology Visualization Techniques in Protege: Experiment Setup and Preliminary Results

paper_content:

The continuing need for more effective information retrieval has lead to the creation of the notions of the semantic web and personalized information management, areas of study that very often employ ontologies to represent the semantic context of a domain. Consequently, the need for effective ontology visualization for design, management and browsing has arisen. There are several ontology visualizations available through the existing ontology management tools, but not as many evaluations to determine their advantages and disadvantages and their suitability for various ontologies and user groups. This work presents the preliminary results of an evaluation of four visualization methods in Protege.
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paper_title: The eyes have it: a task by data type taxonomy for information visualizations

paper_content:

A useful starting point for designing advanced graphical user interfaces is the visual information seeking Mantra: overview first, zoom and filter, then details on demand. But this is only a starting point in trying to understand the rich and varied set of information visualizations that have been proposed in recent years. The paper offers a task by data type taxonomy with seven data types (one, two, three dimensional data, temporal and multi dimensional data, and tree and network data) and seven tasks (overview, zoom, filter, details-on-demand, relate, history, and extracts).
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paper_title: The eyes have it: a task by data type taxonomy for information visualizations

paper_content:

A useful starting point for designing advanced graphical user interfaces is the visual information seeking Mantra: overview first, zoom and filter, then details on demand. But this is only a starting point in trying to understand the rich and varied set of information visualizations that have been proposed in recent years. The paper offers a task by data type taxonomy with seven data types (one, two, three dimensional data, temporal and multi dimensional data, and tree and network data) and seven tasks (overview, zoom, filter, details-on-demand, relate, history, and extracts).
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paper_title: The knowledge model of Protege-2000: combining interoperability and flexibility

paper_content:

Knowledge-based systems have become ubiquitous in recent years. Knowledge-base developers need to be able to share and reuse knowledge bases that they build. Therefore, interoperability among different knowledge-representation systems is essential. The Open Knowledge-Base Connectivity protocol (OKBC) is a common query and construction interface for frame-based systems that facilitates this interoperability. ProtEgE-2000 is an OKBC-compatible knowledge-base-editing environment developed in our laboratory. We describe ProtEgE-2000 knowledge model that makes the import and export of knowledge bases from and to other knowledge-base servers easy. We discuss how the requirements of being a usable and configurable knowledge-acquisition tool affected our decisions in the knowledge-model design. ProtEgE-2000 also has a flexible metaclass architecture which provides configurable templates for new classes in the knowledge base. The use of metaclasses makes ProtEgE-2000 easily extensible and enables its use with other knowledge models. We demonstrate that we can resolve many of the differences between the knowledge models of ProtEgE-2000 and Resource Description Framework (RDF)--a system for annotating Web pages with knowledge elements--by defining a new metaclass set. Resolving the differences between the knowledge models in declarative way enables easy adaptation of ProtEgE-2000 as an editor for other knowledge-representation systems.
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paper_title: OntoEdit: Guiding Ontology Development by Methodology and Inferencing

paper_content:

Ontologies now play an important role for many knowledge-intensive applications for which they provide a source of precisely defined terms. The terms are used for concise communication across people and applications. OntoEdit is an ontology editor that has been developed keeping five main objectives in mind: 1. Ease of use. 2. Methodology-guided development of ontologies. 3. Ontology development with help of inferencing. 4. Development of ontology axioms. 5. Extensibility through plug-in structure. This paper is about the first four of these items.
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paper_title: MoireGraphs: radial focus+context visualization and interaction for graphs with visual nodes

paper_content:

Graph and tree visualization techniques enable interactive exploration of complex relations while communicating topology. However, most existing techniques have not been designed for situations where visual information such as images is also present at each node and must be displayed. This paper presents MoireGraphs to address this need. MoireGraphs combine a new focus+context radial graph layout with a suite of interaction techniques (focus strength changing, radial rotation, level highlighting, secondary foci, animated transitions and node information) to assist in the exploration of graphs with visual nodes. The method is scalable to hundreds of displayed visual nodes.
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paper_title: A multi-perspective software visualization environment

paper_content:

This paper describes a multi-perspective software visualization environment, SHriMP, which combines single view and multi-view techniques to support software exploration at both the architectural and source code levels. SHriMP provides three different views: a primary nested view and two subsidiary views. The primary nested view employs fisheye views of nested graphs, provides contextual cues, and supports general exploration activities. In SHriMP, subsidiary views exist as a searching tool and a relation tracer. These views complement each other and allow programmers to examine a software system from multiple perspectives.
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paper_title: The knowledge model of Protege-2000: combining interoperability and flexibility

paper_content:

Knowledge-based systems have become ubiquitous in recent years. Knowledge-base developers need to be able to share and reuse knowledge bases that they build. Therefore, interoperability among different knowledge-representation systems is essential. The Open Knowledge-Base Connectivity protocol (OKBC) is a common query and construction interface for frame-based systems that facilitates this interoperability. ProtEgE-2000 is an OKBC-compatible knowledge-base-editing environment developed in our laboratory. We describe ProtEgE-2000 knowledge model that makes the import and export of knowledge bases from and to other knowledge-base servers easy. We discuss how the requirements of being a usable and configurable knowledge-acquisition tool affected our decisions in the knowledge-model design. ProtEgE-2000 also has a flexible metaclass architecture which provides configurable templates for new classes in the knowledge base. The use of metaclasses makes ProtEgE-2000 easily extensible and enables its use with other knowledge models. We demonstrate that we can resolve many of the differences between the knowledge models of ProtEgE-2000 and Resource Description Framework (RDF)--a system for annotating Web pages with knowledge elements--by defining a new metaclass set. Resolving the differences between the knowledge models in declarative way enables easy adaptation of ProtEgE-2000 as an editor for other knowledge-representation systems.
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paper_title: Visualization and analysis of microarray and gene ontology data with treemaps

paper_content:

BackgroundThe increasing complexity of genomic data presents several challenges for biologists. Limited computer monitor views of data complexity and the dynamic nature of data in the midst of discovery increase the challenge of integrating experimental results with information resources. The use of Gene Ontology enables researchers to summarize results of quantitative analyses in this framework, but the limitations of typical browser presentation restrict data access.ResultsHere we describe extensions to the treemap design to visualize and query genome data. Treemaps are a space-filling visualization technique for hierarchical structures that show attributes of leaf nodes by size and color-coding. Treemaps enable users to rapidly compare sizes of nodes and sub-trees, and we use Gene Ontology categories, levels of RNA, and other quantitative attributes of DNA microarray experiments as examples. Our implementation of treemaps, Treemap 4.0, allows user-defined filtering to focus on the data of greatest interest, and these queried files can be exported for secondary analyses. Links to model system web pages from Treemap 4.0 enable users access to details about specific genes without leaving the query platform.ConclusionsTreemaps allow users to view and query the data from an experiment on a single computer monitor screen. Treemap 4.0 can be used to visualize various genome data, and is particularly useful for revealing patterns and details within complex data sets.
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paper_title: GoSurfer: a graphical interactive tool for comparative analysis of large gene sets in Gene Ontology space.

paper_content:

The analysis of complex patterns of gene regulation is central to understanding the biology of cells, tissues, and organisms. Patterns of gene regulation pertaining to specific biological processes can be revealed by a variety of experimental strategies, particularly by microarrays and other highly parallel methods, which generate large datasets linking many genes. While methods for detecting gene expression have improved substantially in recent years, understanding the physiological implications of complex patterns in gene expression data is a major challenge. Here we present GoSurfer, an easy-to-use, graphical exploration tool with built-in statistical features that allows a rapid assessment of biological functions represented in large gene sets. GoSurfer takes one or two list(s) of gene identifiers (Affymetrix probe set ID, LocusLink ID or Unigene ID) as input, and retrieves all the Gene Ontology (GO) terms that are associated with the input genes. GoSurfer visualizes these GO terms in a hierarchical tree format. With GoSurfer, users can perform statistical tests to search for the GO terms that are enriched in the annotations of the input genes. These GO terms can be highlighted on the GO tree. Users can manipulate the GO tree in various ways and interactively query the genes that are associated with any GO terms. The user generated graphics can be saved as graphic files, and all the GO information related to the input genes can be exported as test files. GoSurfer is freely available at http://www.gosurfer.org
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paper_title: Tree visualization with tree-maps: 2-d space-filling approach

paper_content:

The traditional approach to representing tree structures is as a rooted, directed graph with the root node at the top of the page and children nodes below the parent node with lines connecting them (Figure 1). Knuth (1968, p. 305-313) has a long discussion about this standard representation, especially why the root is at the top and he offers several alternatives including brief mention of a space-filling approach. However, the remainder of his presentation and most other discussions of trees focus on various node and edge representations. By contrast, this paper deals with a two-dimensional (2-d) space-filling approach in which each node is a rectangle whose area is proportional to some attribute such as node size.
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paper_title: Comparative analysis of gene sets in the gene ontology space under the multiple hypothesis testing framework

paper_content:

The gene ontology (GO) resource can be used as a powerful tool to uncover the properties shared among, and specific to, a list of genes produced by high-throughput functional genomics studies, such as microarray studies. In the comparative analysis of several gene lists, researchers maybe interested in knowing which GO terms are enriched in one list of genes but relatively depleted in another. Statistical tests such as Fisher's exact test or Chi-square test can be performed to search for such GO terms. However, because multiple GO terms are tested simultaneously, individual p-values from individual tests do not serve as good indicators for picking GO terms. Furthermore, these multiple tests are highly correlated, usual multiple testing procedures that work under an independence assumption are not applicable. In this paper we introduce a procedure, based on false discovery rate (FDR), to treat this correlated multiple testing problem. This procedure calculates a moderately conserved estimator of q-value for every GO term. We identify the GO terms with q-values that satisfy a desired level as the significant GO terms. This procedure has been implemented into the GoSurfer software. GoSurfer is a windows based graphical data mining tool. It is freely available at http://www.gosurfer.org.
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paper_title: OntoTrack: Combining browsing and editing with reasoning and explaining for OWL Lite ontologies

paper_content:

OntoTrack is a new browsing and editing "in-one-view" ontology authoring tool that combines a hierarchical graphical layout and instant reasoning feedback for (the most rational fraction of) OWL Lite. OntoTrack provides an animated and zoomable view with context sensitive features like click-able miniature branches or selective detail views together with drag-and-drop editing. Each editing step is instantly synchronized with an external reasoner in order to provide appropriate graphical feedback about relevant modeling consequences. The most recent feature of OntoTrack is an on demand textual explanation for subsumption and equivalence between or unsatisfiability of classes. This paper describes the key features of the current implementation and discusses future work as well as some development issues.
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paper_title: Jambalaya : Interactive visualization to enhance ontology authoring and knowledge acquisition in Protégé

paper_content:

This paper describes the integration of an interactive visualization user interface with a knowledge management tool called Protege. Protege is a general-purpose tool that allows domain experts to build knowledge-based systems by creating and modifying reusable ontologies and problem-solving methods, and by instantiating ontologies to construct knowledge bases. The SHriMP (Simple Hierarchical Multi-Perspective) visualization technique was designed to enhance how people browse, explore and interact with complex information spaces. Although SHriMP is information independent, its primary use to date has been for visualizing and documenting software programs. The paper describes how we have applied software visualization techniques to more general knowledge domains. It is hoped that the integrated environment (called Jambalaya) will result in an easier to use and more powerful environment to support ontology evolution and knowledge acquisition. An example scenario of how Jambalaya can be applied to knowledge acquisition is provided.
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paper_title: OZONE: a zoomable interface for navigating ontology information

paper_content:

We present OZONE (Zoomable Ontology Navigator), for searching and browsing ontological information. OZONE visualizes query conditions and provides interactive, guided browsing for DAML (DARPA Agent Markup Language) ontologies on the Web. To visually represent objects in DAML, we define a visual model for its classes, properties and relationships between them. Properties can be expanded into classes for query refinement. The visual query can be formulated incrementally as users explore class and property structures interactively. Zoomable interface techniques are employed for effective navigation and usability.
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paper_title: Visual Displays for Browsing RDF Documents

paper_content:

Hyperbolic browsers are motivated by the “Circle Limit IV” woodcut of M.C. Escher. The hyperbolic tree view was introduced in graph drawing by Lamping and Rao [2] who observed that large structures could be compactly displayed by projecting a tree onto a hyperbolic plane. The effect of the projection is that components appear diminishing in size and radius exponentially the further they move from the centre of the diagram. The arguments for the hyperbolic display are twofold: an order of magnitude more nodes of a tree can be rendered in the same display space and the focus is maintained on the central vertex of the display and its immediate neighbourhood. The hyperbolic view is particularly useful for hierarchical diagrams with large numbers of leaves and branches and where neighbourhood relationships are meaningful. Examples of the hyperbolic view are INXIGHT’s Star Tree1 and HYPERPROF2. Given that the pure hyperbolic geometric projection is patented, projection onto a sphere, and diminishing radial layout views are the drawing approaches we have experimented with. Recent interest in the Semantic Web has invigorated interest in programs that render ontological data sources (structured metadata) in the style of semantic networks well known in AI. The ONTOBROKER [1] project used a hyperbolic browser to view semantic relationships between frames in F-Logic. ONTORAMA traces its lineage to the ONTOBROKER3 Java source code, but the code has been substantially re-written since 1999. The ONTORAMA effort involved refactoring the Java for the WEBKB-2 project [3, 4] which uses its own internal formats (conceptual graphs).
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paper_title: CropCircles: Topology Sensitive Visualization of OWL Class Hierarchies

paper_content:

OWL ontologies present many interesting visualization challenges. Here we present CropCircles, a technique designed to view the class hierarchies in ontologies as trees. We place special emphasis on topology understanding when designing the tool. We drew inspiration from treemaps, but made substantial changes in the representation and layout. Most notably, the spacefillingness of treemap is relaxed in exchange for visual clarity. We outline the problem scape of visualizing ontology hierarchies, note the requirements that go into the design of the tool, and discuss the interface and implementation. Finally, through a controlled experiment involving tasks common to understanding ontologies, we show the benefits of our design.
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paper_title: TreePlus: Interactive Exploration of Networks with Enhanced Tree Layouts

paper_content:

Despite extensive research, it is still difficult to produce effective interactive layouts for large graphs. Dense layout and occlusion make food Webs, ontologies and social networks difficult to understand and interact with. We propose a new interactive visual analytics component called TreePlus that is based on a tree-style layout. TreePlus reveals the missing graph structure with visualization and interaction while maintaining good readability. To support exploration of the local structure of the graph and gathering of information from the extensive reading of labels, we use a guiding metaphor of "plant a seed and watch it grow." It allows users to start with a node and expand the graph as needed, which complements the classic overview techniques that can be effective at (but often limited to) revealing clusters. We describe our design goals, describe the interface and report on a controlled user study with 28 participants comparing TreePlus with a traditional graph interface for six tasks. In general, the advantage of TreePlus over the traditional interface increased as the density of the displayed data increased. Participants also reported higher levels of confidence in their answers with TreePlus and most of them preferred TreePlus
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paper_title: The Hyperbolic Browser: A Focus � Context Technique for Visualizing Large Hierarchies

paper_content:

We present a new focus 1 context technique based on hyperbolic geometry for visualizing and manipulating large hierarchies . Our technique assigns more display space to a portion of the hierarchy while still embedding it in the context of the entire hierarchy . We lay out the hierarchy in a uniform way on a hyperbolic plane and map this plane onto a display region . The chosen mapping provides a fisheye distortion that supports a smooth blending of focus and context . We have deveoped ef fective procedures for manipulating the focus using pointer clicks as well as interactive dragging and for smoothly animating transitions across such manipulation . Enhancements to the core mechanisms provide support for multiple foci , control of the tradeof f between node density and node display space , and for visualizing graphs by transforming them into trees .
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paper_title: H3: laying out large directed graphs in 3D hyperbolic space

paper_content:

We present the H3 layout technique for drawing large directed graphs as node-link diagrams in 3D hyperbolic space. We can lay out much larger structures than can be handled using traditional techniques for drawing general graphs because we assume a hierarchical nature of the data. We impose a hierarchy on the graph by using domain-specific knowledge to find an appropriate spanning tree. Links which are not part of the spanning tree do not influence the layout but can be selectively drawn by user request. The volume of hyperbolic 3-space increases exponentially, as opposed to the familiar geometric increase of euclidean 3-space. We exploit this exponential amount of room by computing the layout according to the hyperbolic metric. We optimize the cone tree layout algorithm for 3D hyperbolic space by placing children on a hemisphere around the cone mouth instead of on its perimeter. Hyperbolic navigation affords a Focus+Context view of the structure with minimal visual clutter. We have successfully laid out hierarchies of over 20,000 nodes. Our implementation accommodates navigation through graphs too large to be rendered interactively by allowing the user to explicitly prune or expand subtrees.
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paper_title: Botanical visualization of huge hierarchies

paper_content:

A new method for the visualization of huge hierarchical data structures is presented. The method is based on the observation that we can easily see the branches, leaves and their arrangement in a botanical tree, despite of the large number of elements. The strand model of Holton is used to convert an abstract tree into a geometric model. Non-leaf nodes are mapped to branches and child nodes to sub-branches. A naive application of this model leads to unsatisfactory results, hence it is tailored to suit our purposes better. Continuing branches are emphasized, long branches are contracted, and sets of leaves are shown as fruit. The method is applied to the visualization of directory structures. The elements, directories and files, as well as their relations can easily be extracted, thereby showing that the use of methods from botanical modeling can be effective for information visualization.
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paper_title: Cone Trees: animated 3D visualizations of hierarchical information

paper_content:

The task of managing and accessing large information spaces is a problem in large scale cognition. Enwrging technologies for 3D visualization and interactive aninlaiion offer potential solutions to this problenl, especially when the structure of the information can be visualized. We describe one of these Information Visualtzaiion techniques, called the Cone Tree, which is used for visualizing hierarchical information structures. The hierarchy is presented in 3D to nlaxilnize effective use of available screen space and enable visualization of the whole structure. Interactive aninlation is used (,o shift sonle of the user’s cognitive load to the human perceptual system,
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paper_title: Reconfigurable disc trees for visualizing large hierarchical information space

paper_content:

We present a new visualization technique, called RDT (Reconfigurable Disc Tree) which can alleviate the disadvantages of cone trees significantly for large hierarchies while maintaining its context of using 3D depth. In RDT, each node is associated with a disc, around which its children are placed. Using discs instead of cones as the basic shape in RDT has several advantages: significant reduction of occluded region, sharp increase in number of displayed nodes, and easy projection onto plane without visual overlapping. We show that RDT can greatly enhance user perception by transforming its shapes dynamically in several ways: (1) disc tree which can significantly reduce the occluded region by the foreground objects; (2) compact disc tree which can increase the number of nodes displayed on the screen; and (3) plane disc tree which can be mapped onto the plane without visual overlapping. We describe an implementation of our visualization system called VISIT (Visual Information System for reconfigurable dIsc tree). It provides 2D and 3D layouts for RDT and various user interface features such as tree reconfiguration, tree transformation, tree shading, viewing transformation, animation, selection and browsing which can enhance the user perception and navigation capabilities. We also evaluate our system using the following three metrics: percentage of occlusion, density of displayed nodes on a screen, and number of identifiable nodes.
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paper_title: Visual exploration of large hierarchies with information pyramids

paper_content:

Information pyramids compactly visualise large hierarchical structures in three dimensions using pyramid-like structures, which grow upwards as the hierarchy deepens. A plateau represents the root of the tree; other, smaller plateaus arranged on top of it represent its subtrees. Separate glyphs are used to represent leaf nodes such as files or documents and navigational facilities are provided for interactive exploration. Two generations of information pyramids prototype are described and discussed.
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paper_title: OntoSphere: more than a 3D ontology visualization tool

paper_content:

In this paper a new approach to ontology visualization is introduced, using a more than 3-dimensional space. The ontology information is represented on a 3D view-port enriched by visual cues. A preliminary application based on the presented principles is described, and results show that the approach is feasible and can actually lead to a more effective modeling process and to an easy detection of “conceptual inconsistencies”. The opinions of domain experts are also quite positive and seem to indicate that the approach is promising and can be extended for creating “user friendly” ontology editors for people with low ICT skills.
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paper_title: Interacting with Huge Hierarchies: Beyond Cone Trees

paper_content:

Abstract This paper describes an implementation of a toolfor visualizing and interacting with huge information hier-archies, and some preliminary empirical evaluation of thetool’s efficacy. Existing systems for visualizing huge hier-archies using cone trees ‘‘break down” once the hierarchyto be displayed exceeds roughly 1000 nodes, due to in-creasing visual clutter. This paper describes a systemcalledfsviz which visualizes arbitrarily large hierarchieswhile retaining user control. This is accomplished by aug-menting cone trees with several graphical and interactiontechniques: usage-based filtering, animated zooming,hand-coupled rotation, fish-eye zooming, coalescing of dis-tant nodes, texturing, effective use of colour for depth cue-ing, and the applications of dynamic queries. Thefsvizsystem also improves upon earlier cone tree visualizationsystems through a more elaborate node layout algorithm.This algorithm enhances the usefulness of cone tree visual-ization for large hierarchies by all but eliminating clutter.
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paper_title: Polyarchy visualization: visualizing multiple intersecting hierarchies

paper_content:

We describe a new information structure composed of multiple intersecting hierarchies, which we call Polyarchies. Visualizing polyarchies enables use of novel views for discovery of relationships which are very difficult using existing hierarchy visualization tools. This paper will describe the visualization design and system architecture challenges as well as our current solutions. A Mid-Tier Cache architecture is used as a "polyarchy server" which supports a novel web-based polyarchy visualization technique, called Visual Pivot. A series of five user studies guided iterative design of Visual Pivot
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paper_title: Tracking changes during ontology evolution

paper_content:

As ontology development becomes a collaborative process, developers face the problem of maintaining versions of ontologies akin to maintaining versions of software code or versions of documents in large projects. Traditional versioning systems enable users to compare versions, examine changes, and accept or reject changes. However, while versioning systems usually treat software code and text documents as text files, a versioning system for ontologies must compare and present structural changes rather than changes in text representation of ontologies. In this paper, we present the PromptDiff ontology-versioning environment, which address these challenges. PromptDiff includes an efficient version-comparison algorithm that produces a structural diff between ontologies. The results are presented to the users through an intuitive user interface for analyzing the changes that enables users to view concepts and groups of concepts that were added, deleted, and moved, distinguished by their appearance and with direct access to additional information characterizing the change. The users can then act on the changes, accepting or rejecting them. We present results of a pilot user study that demonstrate the effectiveness of the tool for change management. We discuss design principles for an end-to-end ontology-versioning environment and position ontology versioning as a component in a general ontology-management framework.
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paper_title: User Experiments with Tree Visualization Systems

paper_content:

This paper describes a comparative experiment with five well-known tree visualization systems, and Windows Explorer as a baseline system. Subjects performed tasks relating to the structure of a directory hierarchy, and to attributes of files and directories. Task completion times, correctness and user satisfaction were measured, and video recordings of subjects' interaction with the systems were made. Significant system and task type effects and an interaction between system and task type were found. Qualitative analyses of the video recordings were thereupon conducted to determine reasons for the observed differences, resulting in several findings and design recommendations as well as implications for future experiments with tree visualization systems
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paper_title: A Comparative Study of Four Ontology Visualization Techniques in Protege: Experiment Setup and Preliminary Results

paper_content:

The continuing need for more effective information retrieval has lead to the creation of the notions of the semantic web and personalized information management, areas of study that very often employ ontologies to represent the semantic context of a domain. Consequently, the need for effective ontology visualization for design, management and browsing has arisen. There are several ontology visualizations available through the existing ontology management tools, but not as many evaluations to determine their advantages and disadvantages and their suitability for various ontologies and user groups. This work presents the preliminary results of an evaluation of four visualization methods in Protege.
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paper_title: SpaceTree: supporting exploration in large node link tree, design evolution and empirical evaluation

paper_content:

We present a novel tree browser that builds on the conventional node link tree diagrams. It adds dynamic rescaling of branches of the tree to best fit the available screen space, optimized camera movement, and the use of preview icons summarizing the topology of the branches that cannot be expanded. In addition, it includes integrated search and filter functions. This paper reflects on the evolution of the design and highlights the principles that emerged from it. A controlled experiment showed benefits for navigation to already previously visited nodes and estimation of overall tree topology.
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paper_title: An Evaluation of Cone Trees

paper_content:

Cone Trees are an appealing interactive 3D visualisation technique for hierarchical data structures. They were originally intended to maximise effective use of available screen space and to better exploit the abilities of the human perceptual system. Prior work has focused on the fidelity of the visualisation rather than providing empirical user studies. This paper describes the design, implementation and evaluation of a lowfidelity animated and rapidly interactive 3D cone tree system. Results of the evaluation show that our subjects were slower at locating data using cone trees than when using a ‘normal’ tree browser, and that their performance deteriorated rapidly as the branching factor of the data-structure increased. Qualitative results, however, indicate that the subjects were enthusiastic about the cone tree visualisation and that they felt it provided a better ‘feel’ for the structure of the information space.
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paper_title: User Experiments with Tree Visualization Systems

paper_content:

This paper describes a comparative experiment with five well-known tree visualization systems, and Windows Explorer as a baseline system. Subjects performed tasks relating to the structure of a directory hierarchy, and to attributes of files and directories. Task completion times, correctness and user satisfaction were measured, and video recordings of subjects' interaction with the systems were made. Significant system and task type effects and an interaction between system and task type were found. Qualitative analyses of the video recordings were thereupon conducted to determine reasons for the observed differences, resulting in several findings and design recommendations as well as implications for future experiments with tree visualization systems
---
paper_title: A Comparative Study of Four Ontology Visualization Techniques in Protege: Experiment Setup and Preliminary Results

paper_content:

The continuing need for more effective information retrieval has lead to the creation of the notions of the semantic web and personalized information management, areas of study that very often employ ontologies to represent the semantic context of a domain. Consequently, the need for effective ontology visualization for design, management and browsing has arisen. There are several ontology visualizations available through the existing ontology management tools, but not as many evaluations to determine their advantages and disadvantages and their suitability for various ontologies and user groups. This work presents the preliminary results of an evaluation of four visualization methods in Protege.
---
paper_title: SpaceTree: supporting exploration in large node link tree, design evolution and empirical evaluation

paper_content:

We present a novel tree browser that builds on the conventional node link tree diagrams. It adds dynamic rescaling of branches of the tree to best fit the available screen space, optimized camera movement, and the use of preview icons summarizing the topology of the branches that cannot be expanded. In addition, it includes integrated search and filter functions. This paper reflects on the evolution of the design and highlights the principles that emerged from it. A controlled experiment showed benefits for navigation to already previously visited nodes and estimation of overall tree topology.
---
paper_title: Cone Trees: animated 3D visualizations of hierarchical information

paper_content:

The task of managing and accessing large information spaces is a problem in large scale cognition. Enwrging technologies for 3D visualization and interactive aninlaiion offer potential solutions to this problenl, especially when the structure of the information can be visualized. We describe one of these Information Visualtzaiion techniques, called the Cone Tree, which is used for visualizing hierarchical information structures. The hierarchy is presented in 3D to nlaxilnize effective use of available screen space and enable visualization of the whole structure. Interactive aninlation is used (,o shift sonle of the user’s cognitive load to the human perceptual system,
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paper_title: User Experiments with Tree Visualization Systems

paper_content:

This paper describes a comparative experiment with five well-known tree visualization systems, and Windows Explorer as a baseline system. Subjects performed tasks relating to the structure of a directory hierarchy, and to attributes of files and directories. Task completion times, correctness and user satisfaction were measured, and video recordings of subjects' interaction with the systems were made. Significant system and task type effects and an interaction between system and task type were found. Qualitative analyses of the video recordings were thereupon conducted to determine reasons for the observed differences, resulting in several findings and design recommendations as well as implications for future experiments with tree visualization systems
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paper_title: Beamtrees: Compact Visualization of Large Hierarchies

paper_content:

Beamtrees are a new method for the visualization of large hierarchical data sets, such as directory structures and organization structures. Nodes are shown as stacked circular beams such that both the hierarchical structure as well as the size of nodes are depicted. The dimensions of beams are calculated using a variation of the treemap algorithm. Both a two-dimensional and a three-dimensional variant are presented. A small user study indicated that beamtrees are significantly more effective than nested treemaps and cushion treemaps for the extraction of global hierarchical information.
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paper_title: TreePlus: Interactive Exploration of Networks with Enhanced Tree Layouts

paper_content:

Despite extensive research, it is still difficult to produce effective interactive layouts for large graphs. Dense layout and occlusion make food Webs, ontologies and social networks difficult to understand and interact with. We propose a new interactive visual analytics component called TreePlus that is based on a tree-style layout. TreePlus reveals the missing graph structure with visualization and interaction while maintaining good readability. To support exploration of the local structure of the graph and gathering of information from the extensive reading of labels, we use a guiding metaphor of "plant a seed and watch it grow." It allows users to start with a node and expand the graph as needed, which complements the classic overview techniques that can be effective at (but often limited to) revealing clusters. We describe our design goals, describe the interface and report on a controlled user study with 28 participants comparing TreePlus with a traditional graph interface for six tasks. In general, the advantage of TreePlus over the traditional interface increased as the density of the displayed data increased. Participants also reported higher levels of confidence in their answers with TreePlus and most of them preferred TreePlus
---
paper_title: A Comparative Study of Four Ontology Visualization Techniques in Protege: Experiment Setup and Preliminary Results

paper_content:

The continuing need for more effective information retrieval has lead to the creation of the notions of the semantic web and personalized information management, areas of study that very often employ ontologies to represent the semantic context of a domain. Consequently, the need for effective ontology visualization for design, management and browsing has arisen. There are several ontology visualizations available through the existing ontology management tools, but not as many evaluations to determine their advantages and disadvantages and their suitability for various ontologies and user groups. This work presents the preliminary results of an evaluation of four visualization methods in Protege.
---
paper_title: Interacting with Huge Hierarchies: Beyond Cone Trees

paper_content:

Abstract This paper describes an implementation of a toolfor visualizing and interacting with huge information hier-archies, and some preliminary empirical evaluation of thetool’s efficacy. Existing systems for visualizing huge hier-archies using cone trees ‘‘break down” once the hierarchyto be displayed exceeds roughly 1000 nodes, due to in-creasing visual clutter. This paper describes a systemcalledfsviz which visualizes arbitrarily large hierarchieswhile retaining user control. This is accomplished by aug-menting cone trees with several graphical and interactiontechniques: usage-based filtering, animated zooming,hand-coupled rotation, fish-eye zooming, coalescing of dis-tant nodes, texturing, effective use of colour for depth cue-ing, and the applications of dynamic queries. Thefsvizsystem also improves upon earlier cone tree visualizationsystems through a more elaborate node layout algorithm.This algorithm enhances the usefulness of cone tree visual-ization for large hierarchies by all but eliminating clutter.
---
paper_title: A Comparative Study of Four Ontology Visualization Techniques in Protege: Experiment Setup and Preliminary Results

paper_content:

The continuing need for more effective information retrieval has lead to the creation of the notions of the semantic web and personalized information management, areas of study that very often employ ontologies to represent the semantic context of a domain. Consequently, the need for effective ontology visualization for design, management and browsing has arisen. There are several ontology visualizations available through the existing ontology management tools, but not as many evaluations to determine their advantages and disadvantages and their suitability for various ontologies and user groups. This work presents the preliminary results of an evaluation of four visualization methods in Protege.
---
paper_title: SpaceTree: supporting exploration in large node link tree, design evolution and empirical evaluation

paper_content:

We present a novel tree browser that builds on the conventional node link tree diagrams. It adds dynamic rescaling of branches of the tree to best fit the available screen space, optimized camera movement, and the use of preview icons summarizing the topology of the branches that cannot be expanded. In addition, it includes integrated search and filter functions. This paper reflects on the evolution of the design and highlights the principles that emerged from it. A controlled experiment showed benefits for navigation to already previously visited nodes and estimation of overall tree topology.
---
paper_title: User Experiments with Tree Visualization Systems

paper_content:

This paper describes a comparative experiment with five well-known tree visualization systems, and Windows Explorer as a baseline system. Subjects performed tasks relating to the structure of a directory hierarchy, and to attributes of files and directories. Task completion times, correctness and user satisfaction were measured, and video recordings of subjects' interaction with the systems were made. Significant system and task type effects and an interaction between system and task type were found. Qualitative analyses of the video recordings were thereupon conducted to determine reasons for the observed differences, resulting in several findings and design recommendations as well as implications for future experiments with tree visualization systems
---
paper_title: Beamtrees: Compact Visualization of Large Hierarchies

paper_content:

Beamtrees are a new method for the visualization of large hierarchical data sets, such as directory structures and organization structures. Nodes are shown as stacked circular beams such that both the hierarchical structure as well as the size of nodes are depicted. The dimensions of beams are calculated using a variation of the treemap algorithm. Both a two-dimensional and a three-dimensional variant are presented. A small user study indicated that beamtrees are significantly more effective than nested treemaps and cushion treemaps for the extraction of global hierarchical information.
---
paper_title: CropCircles: Topology Sensitive Visualization of OWL Class Hierarchies

paper_content:

OWL ontologies present many interesting visualization challenges. Here we present CropCircles, a technique designed to view the class hierarchies in ontologies as trees. We place special emphasis on topology understanding when designing the tool. We drew inspiration from treemaps, but made substantial changes in the representation and layout. Most notably, the spacefillingness of treemap is relaxed in exchange for visual clarity. We outline the problem scape of visualizing ontology hierarchies, note the requirements that go into the design of the tool, and discuss the interface and implementation. Finally, through a controlled experiment involving tasks common to understanding ontologies, we show the benefits of our design.
---
paper_title: SpaceTree: supporting exploration in large node link tree, design evolution and empirical evaluation

paper_content:

We present a novel tree browser that builds on the conventional node link tree diagrams. It adds dynamic rescaling of branches of the tree to best fit the available screen space, optimized camera movement, and the use of preview icons summarizing the topology of the branches that cannot be expanded. In addition, it includes integrated search and filter functions. This paper reflects on the evolution of the design and highlights the principles that emerged from it. A controlled experiment showed benefits for navigation to already previously visited nodes and estimation of overall tree topology.
---
paper_title: H3: laying out large directed graphs in 3D hyperbolic space

paper_content:

We present the H3 layout technique for drawing large directed graphs as node-link diagrams in 3D hyperbolic space. We can lay out much larger structures than can be handled using traditional techniques for drawing general graphs because we assume a hierarchical nature of the data. We impose a hierarchy on the graph by using domain-specific knowledge to find an appropriate spanning tree. Links which are not part of the spanning tree do not influence the layout but can be selectively drawn by user request. The volume of hyperbolic 3-space increases exponentially, as opposed to the familiar geometric increase of euclidean 3-space. We exploit this exponential amount of room by computing the layout according to the hyperbolic metric. We optimize the cone tree layout algorithm for 3D hyperbolic space by placing children on a hemisphere around the cone mouth instead of on its perimeter. Hyperbolic navigation affords a Focus+Context view of the structure with minimal visual clutter. We have successfully laid out hierarchies of over 20,000 nodes. Our implementation accommodates navigation through graphs too large to be rendered interactively by allowing the user to explicitly prune or expand subtrees.
---
paper_title: User Experiments with Tree Visualization Systems

paper_content:

This paper describes a comparative experiment with five well-known tree visualization systems, and Windows Explorer as a baseline system. Subjects performed tasks relating to the structure of a directory hierarchy, and to attributes of files and directories. Task completion times, correctness and user satisfaction were measured, and video recordings of subjects' interaction with the systems were made. Significant system and task type effects and an interaction between system and task type were found. Qualitative analyses of the video recordings were thereupon conducted to determine reasons for the observed differences, resulting in several findings and design recommendations as well as implications for future experiments with tree visualization systems
---
paper_title: A Comparative Study of Four Ontology Visualization Techniques in Protege: Experiment Setup and Preliminary Results

paper_content:

The continuing need for more effective information retrieval has lead to the creation of the notions of the semantic web and personalized information management, areas of study that very often employ ontologies to represent the semantic context of a domain. Consequently, the need for effective ontology visualization for design, management and browsing has arisen. There are several ontology visualizations available through the existing ontology management tools, but not as many evaluations to determine their advantages and disadvantages and their suitability for various ontologies and user groups. This work presents the preliminary results of an evaluation of four visualization methods in Protege.
---
paper_title: Task taxonomy for graph visualization

paper_content:

Our goal is to define a list of tasks for graph visualization that has enough detail and specificity to be useful to: 1) designers who want to improve their system and 2) to evaluators who want to compare graph visualization systems. In this paper, we suggest a list of tasks we believe are commonly encountered while analyzing graph data. We define graph specific objects and demonstrate how all complex tasks could be seen as a series of low-level tasks performed on those objects. We believe that our taxonomy, associated with benchmark datasets and specific tasks, would help evaluators generalize results collected through a series of controlled experiments.
---
paper_title: A Comparative Study of Four Ontology Visualization Techniques in Protege: Experiment Setup and Preliminary Results

paper_content:

The continuing need for more effective information retrieval has lead to the creation of the notions of the semantic web and personalized information management, areas of study that very often employ ontologies to represent the semantic context of a domain. Consequently, the need for effective ontology visualization for design, management and browsing has arisen. There are several ontology visualizations available through the existing ontology management tools, but not as many evaluations to determine their advantages and disadvantages and their suitability for various ontologies and user groups. This work presents the preliminary results of an evaluation of four visualization methods in Protege.
---
paper_title: The eyes have it: a task by data type taxonomy for information visualizations

paper_content:

A useful starting point for designing advanced graphical user interfaces is the visual information seeking Mantra: overview first, zoom and filter, then details on demand. But this is only a starting point in trying to understand the rich and varied set of information visualizations that have been proposed in recent years. The paper offers a task by data type taxonomy with seven data types (one, two, three dimensional data, temporal and multi dimensional data, and tree and network data) and seven tasks (overview, zoom, filter, details-on-demand, relate, history, and extracts).
---
paper_title: SpaceTree: supporting exploration in large node link tree, design evolution and empirical evaluation

paper_content:

We present a novel tree browser that builds on the conventional node link tree diagrams. It adds dynamic rescaling of branches of the tree to best fit the available screen space, optimized camera movement, and the use of preview icons summarizing the topology of the branches that cannot be expanded. In addition, it includes integrated search and filter functions. This paper reflects on the evolution of the design and highlights the principles that emerged from it. A controlled experiment showed benefits for navigation to already previously visited nodes and estimation of overall tree topology.
---
paper_title: Cone Trees: animated 3D visualizations of hierarchical information

paper_content:

The task of managing and accessing large information spaces is a problem in large scale cognition. Enwrging technologies for 3D visualization and interactive aninlaiion offer potential solutions to this problenl, especially when the structure of the information can be visualized. We describe one of these Information Visualtzaiion techniques, called the Cone Tree, which is used for visualizing hierarchical information structures. The hierarchy is presented in 3D to nlaxilnize effective use of available screen space and enable visualization of the whole structure. Interactive aninlation is used (,o shift sonle of the user’s cognitive load to the human perceptual system,
---
paper_title: User Experiments with Tree Visualization Systems

paper_content:

This paper describes a comparative experiment with five well-known tree visualization systems, and Windows Explorer as a baseline system. Subjects performed tasks relating to the structure of a directory hierarchy, and to attributes of files and directories. Task completion times, correctness and user satisfaction were measured, and video recordings of subjects' interaction with the systems were made. Significant system and task type effects and an interaction between system and task type were found. Qualitative analyses of the video recordings were thereupon conducted to determine reasons for the observed differences, resulting in several findings and design recommendations as well as implications for future experiments with tree visualization systems
---
paper_title: OntoSphere: more than a 3D ontology visualization tool

paper_content:

In this paper a new approach to ontology visualization is introduced, using a more than 3-dimensional space. The ontology information is represented on a 3D view-port enriched by visual cues. A preliminary application based on the presented principles is described, and results show that the approach is feasible and can actually lead to a more effective modeling process and to an easy detection of “conceptual inconsistencies”. The opinions of domain experts are also quite positive and seem to indicate that the approach is promising and can be extended for creating “user friendly” ontology editors for people with low ICT skills.
---
paper_title: SpaceTree: supporting exploration in large node link tree, design evolution and empirical evaluation

paper_content:

We present a novel tree browser that builds on the conventional node link tree diagrams. It adds dynamic rescaling of branches of the tree to best fit the available screen space, optimized camera movement, and the use of preview icons summarizing the topology of the branches that cannot be expanded. In addition, it includes integrated search and filter functions. This paper reflects on the evolution of the design and highlights the principles that emerged from it. A controlled experiment showed benefits for navigation to already previously visited nodes and estimation of overall tree topology.
---
paper_title: A Comparative Study of Four Ontology Visualization Techniques in Protege: Experiment Setup and Preliminary Results

paper_content:

The continuing need for more effective information retrieval has lead to the creation of the notions of the semantic web and personalized information management, areas of study that very often employ ontologies to represent the semantic context of a domain. Consequently, the need for effective ontology visualization for design, management and browsing has arisen. There are several ontology visualizations available through the existing ontology management tools, but not as many evaluations to determine their advantages and disadvantages and their suitability for various ontologies and user groups. This work presents the preliminary results of an evaluation of four visualization methods in Protege.
---
paper_title: H3: laying out large directed graphs in 3D hyperbolic space

paper_content:

We present the H3 layout technique for drawing large directed graphs as node-link diagrams in 3D hyperbolic space. We can lay out much larger structures than can be handled using traditional techniques for drawing general graphs because we assume a hierarchical nature of the data. We impose a hierarchy on the graph by using domain-specific knowledge to find an appropriate spanning tree. Links which are not part of the spanning tree do not influence the layout but can be selectively drawn by user request. The volume of hyperbolic 3-space increases exponentially, as opposed to the familiar geometric increase of euclidean 3-space. We exploit this exponential amount of room by computing the layout according to the hyperbolic metric. We optimize the cone tree layout algorithm for 3D hyperbolic space by placing children on a hemisphere around the cone mouth instead of on its perimeter. Hyperbolic navigation affords a Focus+Context view of the structure with minimal visual clutter. We have successfully laid out hierarchies of over 20,000 nodes. Our implementation accommodates navigation through graphs too large to be rendered interactively by allowing the user to explicitly prune or expand subtrees.
---
paper_title: Beamtrees: Compact Visualization of Large Hierarchies

paper_content:

Beamtrees are a new method for the visualization of large hierarchical data sets, such as directory structures and organization structures. Nodes are shown as stacked circular beams such that both the hierarchical structure as well as the size of nodes are depicted. The dimensions of beams are calculated using a variation of the treemap algorithm. Both a two-dimensional and a three-dimensional variant are presented. A small user study indicated that beamtrees are significantly more effective than nested treemaps and cushion treemaps for the extraction of global hierarchical information.
---
paper_title: Interactive information visualization of a million items

paper_content:

Existing information visualization techniques are usually limited to the display of a few thousand items. This article describes new interactive techniques capable of handling a million items (effectively visible and manageable on screen). We evaluate the use of hardware-based techniques available with newer graphics cards, as well as new animation techniques and non-standard graphical features such as stereovision and overlap count. These techniques have been applied to two popular information visualizations: treemaps and scatter plot diagrams; but are generic enough to be applied to other 2D representations as well.
---
paper_title: A Comparative Study of Four Ontology Visualization Techniques in Protege: Experiment Setup and Preliminary Results

paper_content:

The continuing need for more effective information retrieval has lead to the creation of the notions of the semantic web and personalized information management, areas of study that very often employ ontologies to represent the semantic context of a domain. Consequently, the need for effective ontology visualization for design, management and browsing has arisen. There are several ontology visualizations available through the existing ontology management tools, but not as many evaluations to determine their advantages and disadvantages and their suitability for various ontologies and user groups. This work presents the preliminary results of an evaluation of four visualization methods in Protege.
---
paper_title: Interacting with Huge Hierarchies: Beyond Cone Trees

paper_content:

Abstract This paper describes an implementation of a toolfor visualizing and interacting with huge information hier-archies, and some preliminary empirical evaluation of thetool’s efficacy. Existing systems for visualizing huge hier-archies using cone trees ‘‘break down” once the hierarchyto be displayed exceeds roughly 1000 nodes, due to in-creasing visual clutter. This paper describes a systemcalledfsviz which visualizes arbitrarily large hierarchieswhile retaining user control. This is accomplished by aug-menting cone trees with several graphical and interactiontechniques: usage-based filtering, animated zooming,hand-coupled rotation, fish-eye zooming, coalescing of dis-tant nodes, texturing, effective use of colour for depth cue-ing, and the applications of dynamic queries. Thefsvizsystem also improves upon earlier cone tree visualizationsystems through a more elaborate node layout algorithm.This algorithm enhances the usefulness of cone tree visual-ization for large hierarchies by all but eliminating clutter.
---
paper_title: A Comparative Study of Four Ontology Visualization Techniques in Protege: Experiment Setup and Preliminary Results

paper_content:

The continuing need for more effective information retrieval has lead to the creation of the notions of the semantic web and personalized information management, areas of study that very often employ ontologies to represent the semantic context of a domain. Consequently, the need for effective ontology visualization for design, management and browsing has arisen. There are several ontology visualizations available through the existing ontology management tools, but not as many evaluations to determine their advantages and disadvantages and their suitability for various ontologies and user groups. This work presents the preliminary results of an evaluation of four visualization methods in Protege.
---

Title: Ontology visualization methods—a survey

Section 1: INTRODUCTION
Description 1: Introduce the context, motivation, and purpose for the survey on ontology visualization methods.

Section 2: ONTOLOGY DEFINITION
Description 2: Provide a formal definition of ontology, including its components and structure.

Section 3: RELATED WORK
Description 3: Review previous works and surveys that cover visualization techniques relevant to ontologies and other data types.

Section 4: VISUALIZATION TECHNIQUES GROUPING
Description 4: Group and categorize the various visualization techniques used for ontologies.

Section 5: INDENTED LIST
Description 5: Describe the indented list method and its features, focusing on systems like Protégé.

Section 6: NODE--LINK AND TREE
Description 6: Explain node-link and tree visualization techniques, including both 2D and 3D methods, with examples.

Section 7: ZOOMABLE VISUALIZATIONS
Description 7: Discuss zoomable interfaces and their application in ontology visualization.

Section 8: SPACE FILLING
Description 8: Detail space-filling visualization techniques and how they represent hierarchical data.

Section 9: CONTEXT + FOCUS AND DISTORTION TECHNIQUES
Description 9: Explore the focus + context and distortion techniques applied to ontology visualization. 

Section 10: INFORMATION LANDSCAPES
Description 10: Present the information landscape metaphor and its use in visualizing ontologies.

Section 11: VISUALIZING TIME IN THE CONTEXT OF ONTOLOGIES
Description 11: Summarize approaches to representing the evolution of ontologies over time.

Section 12: DISCUSSION-METHOD ADVANTAGES & DISADVANTAGES
Description 12: Discuss the advantages and disadvantages of each visualization method category.

Section 13: TASK SUPPORT
Description 13: Analyze which visualization methods best support different ontology-related tasks.

Section 14: 2D VS 3D
Description 14: Compare and contrast the effectiveness of 2D versus 3D visualizations for ontologies.

Section 15: NAVIGATION AND INTERACTION ISSUES
Description 15: Explore common navigation and interaction challenges in ontology visualization.

Section 16: SCALABILITY ISSUES
Description 16: Address the scalability of different visualization methods for large ontologies.

Section 17: REASONING
Description 17: Discuss the integration of reasoning capabilities with ontology visualization.

Section 18: CONCLUSIONS--FUTURE WORK
Description 18: Summarize the findings of the survey and suggest directions for future research.