Author : David Loup
Date : 01/10/2004
The purpose of this document is to present the status of
the VisOn application, its work in progress and the
important parts of the program which would need to be improved, completed or updated. We will try and
describe the structure of the program for the next
programmer to be able to modify easily certain parts of the software.
Content of this file :
1. Package Description
2. JGraph
3. Functionalities
4. Algorithmic improvements
5. Interface improvement
6. License
1. Package Description
Here follows the description of the different
packages which are part of the VisOn application.
ca.umontreal.iro.vison.export :
Classes to export graphs in PNG or JPG images using
the functions from the JGraph API. PDF and SVG to be
added. The package also contains all the program parts
which need to read files, i.e. the classes which load
the different available algorithms, the default weights
configuration and the similarity functions. It should so
be renamed ca.umontreal.iro.vison.io, or something like
that.
ca.umontreal.iro.vison.gui :
The main package containing all the graphical
classes. The GraphTests class is used to perform tests
on the JGraph API and is independant. The OLGraph
class is not a graphical one but is the most important :
it extends the JGraph basic class and builds a graph to
be displayed, from the OL-Graph object built by the
classes in the package ca.umontreal.iro.olgraph.
GUI is the main class and is the one that must be
run. GUIParameters defines the colors associated to the
nodes and other constants. An XML file would be a better
option...
ca.umontreal.iro.vison.nodesInfo :
A part of the program which displays information
about nodes when they are clicked. This part is not used
anymore and had been put aside for priority reasons, but
it could be interesting to keep developing it and
improving it.
ca.umontreal.iro.vison.jgraph :
All the JGraph extensions created by David Loup,
sometimes from code available in the JGraph tutorial,
the FAQ of the forums. Contains custom shapes for nodes,
and improved edges management.
ca.umontreal.iro.vison.layout :
The package containing the different layout
algorithms. Right now, only the Sugiyama algorithm is
used but it is not optimal. New algorithms developed by
the JGraph community should be imported here.
ca.umontreal.iro.vison.draw :
The classes of this package creates the graphical
forms of the different nodes encountered when analyzing
the OL-Graph.
ca.umontreal.iro.vison.util :
Some utilities functions shared by different classes
should be put here. Only contains the File filter now.
2. JGraph
In order to
represent the ontologies as OL-Graph, we decided to use
the JGraph API
which deals with the positioning of nodes, drag
and drop, resizing, etc. The JGraph community is very
active and keeps releasing new versions of their
softwares. When the project began (July 2004) we worked with JGraph 4 and now a new version is available
with many improvements. The first thing to do would be
to import this new version into VisOn.
First, one
must get the binary jar file from
Sourceforge. Here is the
list of the different subprojects concerning JGraph :
- JGraph, the base API to build graph
- JGraph Pad, a graph editor. Although we don't edit the
graphs we generate, this part has VERY useful code : PDF
and SVG exportation for example, to be imported in VisOn.
- JGraphAddons : The parts of these addons which
interest us particularly are the new shapes (Ellipse,
Diamonds) and the layout algorithms. Below is the current status of these parts.
The package ca.umontreal.iro.vison.jgraph contains all
the updates of the JGraph classes required by our
application. That is, the custom shapes (Ellipse, Diamonds, and new Rectangles to make a more coherent
look), and new Edges classes to avoid overlapping edges.
The new version of JGraphaddons probably offers these new shapes, it would be better to use theirs for
future support and compastibility. Nevertheless, the
present source code should be kept somewhere and could
serve as a model for further developments.
The package ca.umontreal.iro.vison.export contains the
classes used to export generated graphs into JPG or PNG
files, as well as a beginning of code for SVG and PDF (barely functional). Here again, the new version
probably offers better possibilities, but it seems there
need to be some re-enginnering of some classes. It will
probably be the part needing the most work to adapt and
re-engineer the present source code. The export methods
apply to a GPGraph object (used by the GraphPad editor)
and we only work with OLGraph (that extend JGraph)
objects. The Export classes quickly developed tried to
overrule this, but the result is not perfect in SVG (we
cannot scroll when viewing the file) and not usable in
PDF (only a part of the graph is represented).
The package ca.umontreal.iro.vison.layout
contains all the layout algorithms, any new algorithm
should be added here. A layout algorithm is applied
using the static method applyLayout()
JGraphLayoutAlgorithm, with an algorithm object and the
graph as parameters. It's already the current way, so
there is just to import the new algorithms in the new
package and test them.
Finally, it is important to note that the JGraph
programmers are very available : any question asked on
the forums of the sites will probably get a detailed answer, and they have been very helpful during the
development, don't hesitate to ask for help.
3. Functionalities
The most important functionality needing to be
implemented is the visualization of aligned entities
when displaying two ontologies in a parallel way. A
click on an entity from the first ontology should focus the
second graph on the aligned entity. There is not much
code to be done in the GUI, but the implementation of the OL-Graph by Mohamed Touzani needs
to be modified. As the alignment works with OWL objects
(from the OWL API), we will need a hashtable to map OWL objects with OL-Graph nodes. This hashtable
should be correctly built as the construction of the
graph goes.
See the package ca.umontreal.iro.olgraph for further
information.
See the valueChanged() method in the GUI
class, it contains a start, which currently tries and
get in the second graph the cell with the same name as
the one selected in the first graph.
4.
Algorithmic improvements
The algorithm which is building the visual graph from
the OL-Graph has been improved several times but may
benefit from a code factorisation.
5.
Interface improvements
Here again, there is probably some redundant code
which could be packed in external utilities functions.
Moreover, the exceptions should be centralized as far as
possible : every exception thrown could be sent to the
highest part of the program which would deal with it,
most of the time by displaying the error message in a
popup window. Some printStackTrace() calls
remain.
6.
License
The new version of JGraph is now under the LGPL
License. The VisOn application hasn't been released yet,
nor made public, so after importing the new JGraph
version please be careful to include the License in the
release and be sure all the required copyrights are
present in the files.
