Desktop Visualization

Transcription

1 Desktop Visualization KAIA. OLSEN Department of Computing Science, Molde College, N-64 Molde, Norway. ROBERT R. KORFHAGE Department of Information Science, School of Library and Information Science, University of Pittsburgh, Pittsburgh, PA1526, USA Abstract The desktop metaphor, in its original sense, offers the possibility of giving a document a position on the screen. In practice, strict limitations on screen real estate makes it dificult to utilize this content-position relationship. Here, a methodology to overcome these problems of limited screen space is presented. This is achieved by creating an information space based on points-of interest (Pols). The position of a document (icon) is defined through the combined influence from all of the Pols. 1. Introduction The desktop-metaphor introduces the familiar concepts of documents, in- and out-baskets, folders, file cabinets, etc. to the computer screen. The metaphor was developed and implemented by researchers at Xerox PARC, and made known to the public through the Xerox Star system (and its successor Viewpoint). For an interesting description of this pioneer work see Johnson et al. [1989]. As we know, the ideas have had a widespread influence on other user interfaces, such as the MacIntosh and MS Windows interfaces. Some desktop implementations allow documents, represented as icons, to reside anywhere on the screen. This feature may be used to create an information space with a position-to-contents relationship, for example, to place all research oriented documents in one comer, administrative letters in another, etc. This is, of course, similar to the archive system that many of us use on our physical desktops. However, there is a difference between a 2 to 25 square feet office desk and a less than one square foot CRT display, or an even smaller LCD display on a laptop. The strict limits on screen real estate will restrict the numbers of document icons that can reside directly on the desktop. This problem is increased by the need to represent a document through a meaningful icon, for example, where the icon includes the name of the document, a miniature representation of the first page, etc. Such icons may be quite pixelintensive. With the number of files that most of us handle it is impossible to use a positional system. Instead we store files in a folder or directory system, moving away from the desktop metaphor towards a more traditional way of organizing data storage. Icons get a less prominent place and are often reduced to a miniature symbol in front of the file name (such as in MS Windows), defining filetype only. However, in contrast to early computer systems, the file structure is visualized. Many systems also allow for direct manipulation of files and directories, e.g., starting applications by clicking on the appropriate program or data files, moving files by pointtkdrag techniques, etc. The main advantage with these hierarchical desktop systems is that they allow for an organized storage of very many files. This is necessary as larger and cheaper disk space result in a situation where ordinary users save all sorts of information (documents in many versions, and fax messages, etc.). Thus, the number of files may run in the high hundreds or into the thousands on our personal computers. The directory or folder system is convenient as a storage and retrieval system, as long as a file or document falls clearly in one category - one directory. However, often a document naturally belongs to more than one directory. For example, a letter to the department requesting research equipment may be stored in a department directory, a research directory or in a directory that is reserved for documents concerning equipment. The typical directory structure, however, demands that we choose one directory for storing one document. This is made more complicated by the fact that we may choose different directories when storing and retrieving a document. For example, the situation when we write our request letter may bias towards the department direc /94 $ IEEE 239

2 tory. Later, when we are in the process of ordering the equipment, the equipment directory may be our first choice when we try to retrieve the letter. Thus we may find situations when the hierarchical system gives little support for retrieval. Another disadvantage with the hierarchical system is that it represents the physical structure of files and directories. This one-to-one mapping between storage and user interface may have certain advantages, especially when we work with low level operations (performing backup, copying files, giving operating system commands, etc.). However, from the database field we have seen the advantages that follow from a system that have released itself from the limitations of physical storage. By presenting different views of the data, a very flexible system is obtained. We should expect the same features in our desktop interfaces, especially a system that utilizes content awareness in presenting these views. 2. Background Some of the limitations of the traditional desktop are overcome by the use of text-search systems. A lost document, for example, may be found by a keyword search through all directories. Many desktop systems offer this option, but often with limited capabilities. One should, however, expect these systems soon to include the standard Boolean operators or other functions known from information retrieval systems. with permission]. The number of documents in each category will be given within the icon. One advantage with this system is that it presents all query combinations in one display. A disadvantage is that the display is totally rigid, and independent of the document collection. A disadvantage with systems based on Boolean retrieval is the strict categorization. Thus there will be no indication of the strength of relationship between a document and the search terms. A document is either found to comply with a query or not. Rose, Mander and Oren [ address this problem by a system that uses content awareness to arrange or rearrange the desktop in piles. The pile metaphor is based on the notion that people often use piles for a casual arrangement of documents. Users may create piles by moving documents via direct manipulation, similar to what we expect of modern directory based interfaces. However, the pile system goes further in offering retrieval techniques. Users can flip through documents, viewing iconized documents, etc. Visualization techniques are utilized to color the pile using different criteria, such as date and content. Piles may be described to allow for automatic filing, e.g., in a way where a pile gathers incoming documents that match its topic or contents. Piles may automatically be subdivided according to content, by a clustering algorithm. The vector model is used as the underlying model of representation, supporting both subdividing and automatic filing. The pile system allows a more casual filing system than the traditional hierarchical system based on a directory structure. Both browsing functions and the possibility of a dynamic rearrangement of the structure will support document retrieval. However, as with a directory-based system, the pile-system is also based on each document in one pile only. C.rd Figure 1. Query-spreadsheet example. rd In*fAorOl Boolean queries may be improved further by visualization techniques. Spoerri [1993] presents such a system, where all Boolean combinations of a set of search terms are presented in a query spreadsheet, where the terms make out the corners of the spreadsheet area. For example, with search terms A, B, and C all combinations, A and B and C, (A and B) and (not C), A and (not (B or C), etc. are presented as icons in the display. Figure 1 shows an example [from Spoerri 1993, used In the next section we shall introduce a system based on an alternative approach. The VIBE (Visual Information Browsing Environment) methodology redefines the desktop as an information space, based on points-ofinterests (POIs) instead of piles or directories. VIBE will position icons for all documents (or a selected subset) in this information space, such that the POIs are allowed to influence the position of a document icon. In theory, there are no limit on the number of POIs, or - by other words - to the dimensionality of the information space. There is also no theoretical limit on the number of documents that can be visualized. (In practice we have used VIBE to display as many as 2, documents, but in general it becomes difficult to handle displays with a thousand documents or more.) 24

3 As a metaphor for VIBE we may think of an office desk with a number of piles of documents, each pile holding similar documents. Documents that fall clearly within one pile are put on top of this pile. However, if a document is related to more than one pile, it is put between these - closest to the most relevant pile. In this respect VIBE has some similarity to the system described by Rose, Mander and Oren [1992]. The explicit piles, defined by the keywords, on top of the POIs may be compared to their pile metaphor. However, since position is significant in VIBE s information display new piles and documents may be spread out between the POIs. In practice VIBE piles may be seen as sloppy or overflowing, rather than neat stacks of documents. 3. The VIBE methodology The VIBE system requires a quantitative value for the relevance between a document and a POI. In practice POIs are often defined through a number of keywords in a document. Relevance may then be defined as a simple frequency count of these keywords. This score will be computed for each POI on every document, and may be normalized (e.g., by the length of the document) or weighted. However, in principle the system operates independently of how this score value is computed. If one could define, for example, a good measure of relevance or similarity between images, then VIBE could be used directly as a display on a database of images. department B o research equipment E! Figure 2. A (simple) VIBE display A simple VIBE display is shown in Figure 2. Here a small collection of documents is positioned in an information space defined by three POIs: department, equipment and research. Each POI, or concept, is represented by a circle icon, and are defined through a number of keywords. A document icon, a rectangle, is positioned in the information space according to the score (value of influence) on each POI. Documents that have received a score on a single POI only will be positioned on top of this POI. For example, in Figure 2 we find one document icon on top of the department POI, another on the equipment POI. The document whose icon is positioned between equipment and research has received scores on both of these POIs, seemingly with equal strength as it is positioned in the middle of these POIS. The documents that make up the pile in the middle of the display have received scores on all POIs, indicating that these documents have contents that address all concepts. The idea behind this positional methodology is to present an intuitive mapping between document contents and icon position. The position of a document (U, v) is determined by the simple formula: (u,v) =! oci (ui, vi> i= 1 where is the normalized score (Eo: = 1) of this document on POIi, (ui, vi) being the position of this POI. We see that the VIBE display will directly reflect the content of the document collection with regard to the POIs. The piles in VIBE diagram are made up by documents that have similar score values. Their form will reflect the range of possible score values. If the relevance functions return scores in a wide range, as will often be the case if the score is based on a frequency count, the piles will spread out. A lower cardinality will result in neater stacks (overlaying icons are visualized by a line under the first icon, each line representing another document). In the extreme case where relevance is defined as a Boolean value, or 1, VIBE will perform similarly to the query spreadsheet. In a three POI information space, the A and not (B or C) documents will be positioned on top of POI A, the A and B and (not C) in the middle of the line between A and B, and the A and B and C in the middle of the information space defined by the three POIs. In practice VIBE will break down to a query spreadsheet with a Boolean relevance algorithm. (However, in this case the query spreadsheet will have more convenient icons.) Document icons of VIBE are kept simple in order to utilize limited screen space. The size of the icon, however, may vary according to a user defined function, e.g. by the maximum score obtained, the length of the document, etc. In addition icons may be colored, in order to present different categories of documents. Color may also be assigned to a POI. The system will then assign this color to all documents that are influenced by the POI. In addition icons may be colored through a specific search, i.e., as a marker for documents that were found to satisfy the search term. Documents with similar contents, as determined by 24 1

4 A B ment name, directory information or the full text of the document. C Figure 3. Clustering the score-values, will cluster near the same display positions. An example is shown in Figure 3, where a number of documents are visualized in a three POI information display. We find two clusters, one for documents that are (mainly) influenced by A and B, another of documents that are influenced by all three POIs, but seemingly with a domination from POI C. The dimensionality of the visualization is determined by the number of POIs. With three or fewer POIs each icon position will have an unambiguous interpretation with regard to the information space. With more than three POIs, icons for documents with different scorevalues may be placed in the same position. In practice this problem may be reduced by finding appropriate POI positions, by moving POIs or by the use of color. Figure 4. The STAR-option In addition VIBE can visualize the influence from each POI by the STAR-option, as shown in Figure 4. Here influence is shown by the length of a line from the document icon towards POIs that influence the document. Note that these POIs are highlighted. By clicking on a document icon, additional information on the document may be presented, e.g., the docu- Figure 5. Lens option With the LENS-option VIBE will automatically present a pop-up menu with the name of the document (or documents) that the cursor is indicating. An example is shown in Figure 5, where the cursor indicates three different icons. Selecting one of these lens alternatives will have the same effect as clicking on the appropriate icon. For a further discussion of VIBE features and applications see Olsen et al. [ We see that the VIBE display is both a way of visualizing a document collection and an interface to the underlying documents. In this way the system acts as a visual desktop. 4. The desktop VIBE system A snapshot of the Desktop VIBE user interface is shown in Figure 6. The top-part of the window offers functions (through menu or buttons) to control the display, while the bottom part offers filter functions to restrict the documents to be visualized. Even with the low pixel-intensive icons used for documents this may be necessary if too many documents are visualized at the same time. Subsets of the document collection can be specified through: setting a range for the last-modified-date setting a range for the size of the document giving filter terms In Figure 6, for example, we have limited the documents to be visualized to be the documents containing the keywords Molde College and 64 Molde (in practice selecting the college letterhead) and that have been created after A number of POI-sets may be used at the same time, each set defining a display. Icons highlighted in one display will be highlighted in other displays, defining 242

5 Department letters U O n hog. course Visualization course Administration U1 research Visualization research Filter terms: Molde College 64 Molde I i Figure 6. The VIBE user interface links between different displays. Displays may be stored for future reference, for example to study the difference between displays created at different times. Such a study may also be performed by an animation, where the system will run through the indicated time-range and show the complete document collection on each date. The VIBE displays are based on frequency counts performed by a separate initialization program. Considering the POI definitions, the system will automatically perform frequency counts for each document. Document files are separated from other files by specifying file extensions. The user may also specify which directories are to be searched. The initialization program may run as a background job, or may be scheduled to run at night. With fast disks and a limited number of documents it may be practical to start the initialization program directly from VIBE, giving the possibility of creating new POIs interactively. A dedicated text-search processor may, of course, also be used to speed up fre- quency calculations. However, in practice there should be few disadvantages to using precalculated frequency data, since all other operations, such as POI (re)positioning, filter settings, color settings, document retrieval, etc. are performed with instant feedback. 5. Discussion We do not propose VIBE as a replacement for the traditional desktop, which seems to work well in many situations. However, VIBE allows for a much more dynamic organization of the desktop - quite different from the fixed, and often physical, hierarchical desktop. This feature of VIBE may be used present an alternative view of a desktop, for example: 1. In order to get an overview of the desktop documents. 2. As a retrieval mechanism for documents that are hard to find in the hierarchical structure. 243

6 3. To identify similar documents. For many of us, the files stored in our computer system will reflect at least a part of our work. In this way VIBE may be used to give us an overview of the work we have performed. For example, as college professors, we may use VIBE to give an overview of our complete document collection with regard to POIs such as administration, teaching, professional service and research. Each concept may be defined through descriptive terms, or by using keywords that act as indexes for letterheads, course numbers, etc. By the animation option, or by comparing displays of different times, we may see in which direction our (writing) work is progressing. Different categories of documents, e.g. the research papers, may then be studied in more detail in other VIBE diagrams, perhaps with a POI for each research area. From the overview display the click-on-icon option may be used to retrieve single documents, for example while browsing a part of the collection or to find lost documents. We may also create ad hoc displays just for the purpose of identifying special documents, similar to the way we use traditional retrieval mechanisms based on search terms. However while a traditional retrieval system will need quite specialized or distinct terms in order to limit the number of documents that are to be included in the search, VIBE allows for a second visual search phase after the initial query. Thus search terms, as defined by the POIs, may be broad and including. The final search being performed through an investigation of the display, identifying documents in interesting positions, etc. VIBE will, within the limits of the formula for quantifying relevance, position similar documents, as defined by the POIs, together on the display. Thus the system may be used to find different versions of the same document. 6. Conclusion We have presented the VIBE display methodology, not as a replacement for the traditional hierarchical desktop, but in order to present alternative views of a collection of desktop documents. These views may be useful to get an overview over the entire document collection or, for example, to find lost documents, similar documents, etc. These displays are also an interface to the underlying documents. The full text of a document, for example, may be obtained by clicking on a document icon. Acknowledgements We would like to express our sincere appreciation to Solmund Brunstad for his helpful ideas and to student Atle Steffensen for his participation in implementing the VIBE system. References Johnson, J., Roberts, T.L., Verplank, W., Smith, D.C., Irby, C.H., Beard, M. & Mackey, K. (1989) The Xerox Star: A Retrospective, Computer, 22 (9), Olsen, K.A., Hirtle, S.C., Sochats, K.M. and Williams, J.G. (1992). Ideation through Visualization: The VIBE System, Multimedia Review, Vo1.3, No. 3, Rose, D.E., Mander, R., Oren, T., Poncelebn, Salomon, G. & Wong, Y.Y. (1993) Content Awareness in a File System Interface: Implementing the Pile Metaphor for Organizing Information, Proc. Sixteenth Annual International ACM SIGIR Conference on Research and Development in Information Retrieval, Spoerri, A. (1993) Visual Tools for Information Retrieval, Proceedings of 1993 IEEE Symposium on Visual Languages,