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Date: Fri, 13 Dec 1996 17:06:39 GMTServer: NCSA/1.5Content-type: text/htmlLast-modified: Wed, 30 Oct 1996 19:02:14 GMTContent-length: 7077<HTML><HEAD><TITLE>DEVise Model of Visualization</TITLE></HEAD><BODY><H1>Model of Visualization</H1><!WA0><!WA0><!WA0><img src="http://www.cs.wisc.edu/~devise/devise/model.gif" align=middle>The model of visualization is used to design the framework from whichDEVise is constructed. It is also the best way to understand howDEVise functions.<UL><LI><!WA1><!WA1><!WA1><A href="#Stages">Stages of Visualization</A><LI><!WA2><!WA2><!WA2><A href="#File">File</A><LI><!WA3><!WA3><!WA3><A href="#Schema">Schema</A><LI><!WA4><!WA4><!WA4><A href="#TData">TData</A><LI><!WA5><!WA5><!WA5><A href="#Mapping">Mapping</A><LI><!WA6><!WA6><!WA6><A href="#GData">GData</A><LI><!WA7><!WA7><!WA7><A href="#Filter">Visual Filter</A><LI><!WA8><!WA8><!WA8><A href="#View">View</A><LI><!WA9><!WA9><!WA9><A href="#Window">Window</A><LI><!WA10><!WA10><!WA10><A href="#Link">Link</A><LI><!WA11><!WA11><!WA11><A href="#Cursor">Cursor</A></UL><A name="Stages"><H2>Stages of Visualization</H2></A>Visualization in DEVise is divided into stages, each stage supportedby components responsible for the functions of that stage. Thecomponent design is essential to providing the followingfunctionalities of DEVise:<UL><LI>Visualizations are constructed by creating component instances,and interconnections between components.<LI>DEVise is extensible in that new components may be definedand incorporated into its framework. For example, a new type offile, or new way of drawing graphics may be incorporated.<LI>The <!WA12><!WA12><!WA12><A href="http://www.cs.wisc.edu/~devise/devise/visualQuery.html">visual query interface</A> allows the user to save a visualization and apply it to different sets of input files.</UL><P>The stages of creating a visualization are as follows:<OL><LI>Import a <!WA13><!WA13><!WA13><A href="#File">file</A> into DEVise as a textual data(<!WA14><!WA14><!WA14><A href="#TData">TData</A>). The <!WA15><!WA15><!WA15><A href="#Schema">schema</A> isused to describe information about how to import the file.<LI><!WA16><!WA16><!WA16><A href="#Mapping">Mapping</A>TData into graphical Data(<!WA17><!WA17><!WA17><A href="#GData">GData</A>).<LI>Select a <!WA18><!WA18><!WA18><A href="#View">view</A> to display the GData.Assign a <!WA19><!WA19><!WA19><A href="#Filter">visual filter</A> to select which portionof GData are to be viewed.<LI>Arrange views in <!WA20><!WA20><!WA20><A href="#Window">windows</A>.<LI>Create linked axes using <!WA21><!WA21><!WA21><A href="#Link">visual links</A>. Ordisplay relationships between views using <!WA22><!WA22><!WA22><A href="#Cursor">cursors</A>.</OL><A name="File"><H2>File</H2></A>The input file is provided by the user. It is stored on disk in ASCIIformat. An example of an ASCII file containing sin(time) and cos(time)might look like:<TT><BR> # time sin cos<BR>0.000000.2 1.000000.2 0.000000.2<BR>0.017453.2 0.999848.2 0.017452.2<BR>0.034906.2 0.999391.2 0.034898.2<BR>0.052358.2 0.998630.2 0.052334.2<BR>...</TT><A name="Schema"><H2>Schema</H2></A>The schema file describes the layout of an ASCII input file. It isused to convey: name, type, and range of attributes, characters thatseparate the attributes in the file, and characters that should beignored while reading the file. The attribute range information isoptional. For our example file, the schema file looks like:<TT><BR>type Sensor ascii<BR>comment #<BR>whitespace ' '<BR>attr time double hi 1000 lo 0<BR>attr sin double hi 1 lo -1<BR>attr cos double hi 1 lo -1</TT><P>The first line names the file type: Sensor. All sensor files havedata stored in the same format. More than one file type can beimported into DEVise, each having its own schema file. For example, wecan also create a Stock file type to read information about stockprices, with data stored in a different format. The second line tellsDEVise to ignore lines that start with '#'. The third line tellsDEVise that the attributes in the file are separated by whitespaces. DEVise can also read files separated by other delimiters,such as '10,20,20'. The remaining lines describe attribute names,types, and ranges.<A name="TData"><H2>TData</H2></A>A Textual Data (TData) is the representation used by DEVise to accessfiles (or other types of input data). Once a file is imported intoDEVise as a tdata, the user uses the tdata to create visualizations.Different types of input files are input into DEVise and treateduniformly as TData.<P>After selecting the file type, the user is asked to enter an aliasfor the tdata. The default name is the name of the input file,stripped of its path information. After entering the alias, the fileis imported as TData into DEVise.<A name="Mapping"><H2>Mapping</H2></A>A mapping converts TData attributes into graphical data (GData)attributes. The user decides how tdata is visualize by selecting thetdata attributes that map onto the the x, y, color and shape gdataattributes. Notice that a TData can be visualized in more than one wayby creating more than one mapping.<P>For our example, we can create the following example mappings:<BR>sin_vs_time:<BR>x <-- time<BR>y <-- sin<BR> <BR>cos_vs_time:<BR>x <-- time<BR>y <-- cos<BR> <BR>sin_vs_cos<BR>x <-- cos<BR>y <-- sin<P>Once a mapping is created, it can be used on all TData with thesame file type.<A name="GData"><h2>GData</h2></a><!WA23><!WA23><!WA23><img src="http://www.cs.wisc.edu/~devise/devise/gdata.gif" align=middle><P>The graphical data (gdata) is the graphical representation of thetdata. It consists of attributes: x, y, color, pattern, size,orientation, shape, and shape specific attributes.<A name="Filter"><H2>Visual Filter</H2></A>A visual filter defines a query over the graphical data attributes ofthe gdata. Our implementation supports range query over the X and YGData attributes. Use visual filter to specify portions of GData tobe viewed.<A name="View"><H2>View</H2></A>A view is used to display those gdata that fall within the range ofthe visual filter. Currently we have two types of views: Scatter andSortedX. The Scatter view is used to draw a scattered plot. TheSortedX view implements optimizations used to reduce the time used todraw the gdata if the X attribute is sorted.<A name="Window"><H2>Window</H2></A>A window provides the screen real estate used by views to draw thegdata. It it also responsible for arranging views in itsboundaries. Currently, DEVise supports tiled/automatic, vertical, andhorizontal window layouts.<P>A view can be removed from a window to reduce clutter, orbe moved to another window so that related views are broughttogether for comparison.<P>Windows can be duplicated, a very handy feature. <A name="Link"><H2>Link</H2>A link is used to link visual filters so that updating onesynchronously updates all linked visual filters. We have implementedlinks for linked axes, either linked x and/or y axes. However, a linkin theory can be used on any of the of the graphical attributes: x, y,color, size, pattern, orientation, and shape.<A name="Cursor"><H2>Cursor</H2>A cursor can also be used to display the X/Y boundaries of one viewwithin another view. A cursor contains both a source view and adestination view. The source view is where the cursor fetchesinformation about the current view X/Y axes boundaries. The boundariesof the source view are drawn as line segments in the axes of thedestination view. Click in the axes area of the destination view tomove the source view (by changing its visual filter) to the locationclicked.</BODY></HTML>⌨️ 快捷键说明
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