Jeffrey D. McWhirter
Figure 1
shows a screen snapshot of VGrep. The dialog box shown in the
upper part of the figure allows the user to formulate and execute a query. The result
of the query is shown in the main window. In the case of the figure the query is the
same as described above. Each file that matched is displayed in the main window
with the matched lines shown in the bitmap representation. For long files multiple
bitmaps are used. The user can define scaling factors to shrink or expand
the bitmaps along the x or y axis. The maximum file lines per bitmap can also be set by the
user. One can re-execute a search on the same set of files. In this
case the results of the new search are shown as a different color in the original
bitmap file image. This is a useful facility to discover relationships within files
based on different search criteria.
The use of an abstract graphical representation allows the user to see the full
set of files that were matched and provides an abstract picture of the
distribution of the matches in the files. It allows the user to see clusters and
patterns of matches and may provide a higher level of understanding of the file
structure and contents.
The VGrep tool also allows the user to navigate among
the different files by clicking on the pertinent areas of the bitmap file image to
control a textual representation of the file. On the right in the main window of the figure
there are textual views of two of the matched files. As the user clicks on the bitmap
representation the textual view is scrolled to the corresponding line which is
highlighted. The user can also bring up an external text editor through the
bitmap file representation.
FIGURE 2: VGrep Source Code Display
Abstract
Discovering the content and structure of textual files
through keyword based search is a common task of computer users.
However, the results of such a search is often difficult to understand
and to use. This paper describes VGrep,
a tool that facilitates keyword based search through large textual documents.
VGrep provides the ability to formulate queries
and present the results of the queries in an abstract graphical
representation.
Keywords
Word search, visualization.
Introduction
One of the common tasks that programmers and other users of computers
engage in is to search the contents of a set of files
for particular key words or strings.
The result of such a search is typically in a linear textual format
listing the files and the lines that contained the search expression.
For a small number of matches this output is sufficient for most tasks.
However, as the number of matches grows,
understanding the information being presented becomes more difficult.
Furthermore, navigating through the set of files can be a convoluted task
requiring the user to engage in a series of steps (e.g., identifying the
line, bringing up a text viewer for the file, and going to the
line number that is displayed in the search output).
VGrep is a tool that supports keyword based search and navigation of the
results of the search.
In this paper we first present an example textually oriented search and then
describe how VGrep is used to facilitate this search process.
Example
We now discuss a typical scenario of the use of grep, a Unix search
command. Suppose a programmer needs to search for the keyword ibbox in a set
of program source files. The search command might look like this:
grep -i -n ibbox *.C
which causes all of the files ending in .C to be searched in a
non-case sensitive manner for the string ``ibbox''. The output is to include
the line numbers.
A subset of the results of this search is:
...
Gfx.C:1004:ibbox=gRect0;
Gfx.C:1012:if(!parent)SignalChange(ibbox);
...
ShapeGfx.C:804:r.extent=ibbox.extent-2*p;
ShapeGfx.C:807:r.origin=ibbox.origin+p;
...
Of course this is just a small subset of the output. It is quite easy
to match a large number of lines in a multitude of files. The output readily
becomes unmanageable, requiring the reformulation of the search criteria
or limiting the number of searched files. The linear display of the matched
filenames, line numbers and lines can quickly overwhelm the user.
VGrep
VGrep is a tool that allows a user to define and execute a word search on a
set of files. The result of this search is displayed in a graphical format where
each file is shown abstractly as a bitmap. Each line of the bitmap corresponds
to a line in the file and each bit corresponds to a character.
The result search lines are shown highlighted.
This type of abstract graphical display was developed and explored
by Eick et. al. to visualize, among other things, program line statistics
[1] and log files of telecommunication switch
build processes [2].
Displaying Source Code
The VGrep tool also allows for the abstract representation of source code as seen
in
Figure 2
(Note: The length of the file shown in Figure 2 is approximately 1600
lines, the bitmap representation has been been scaled down and color coding is
not shown).
The user provides a file name. This file is parsed and the
result bitmap is color coded based on the type of each line in the file.
The color coding used for comments, pre-processor directives, global
code and procedures can be specified by the user.
A text view of this file can also be brought as described above.
