Frequently Asked Questions on ISGCI

General

How do I cite ISGCI?

If you want to cite a particular page, then you can use the data given in the footer of that page. For the system in general, use the data in the footer of the home page.

I want to look for some particular data in your system, but its query features are too simple for my complicated question. What can I do now?

Answer 1: Please contact us. We might be able to help you by doing a direct query on the database. This will also help us to improve ISGCI, by letting us know the things people actually (want to) do with ISGCI.

Answer 2: The Sage mathematics system contains a copy of the ISGCI database (sage.graphs.isgci), which you can investigate with the full power of Python at your disposal. Note that this database may not be fully up to date in comparison to www.graphclasses.org.

Can I contribute to ISGCI?

Probably. What are your interests? Why don't you drop us an email?

What are those weird g6: texts for every smallgraph?

It is the definition of the graph in graph6 format. You can copy&paste this to import the graph into e.g. Sage or Mathematica. You may need to escape special characters, like backslashes; see the aforementioned links.

The Java application

Which version of Java do I need?

You need at least version 1.6. You can download the latest version of Java here.

When I click on the application, I get a download dialog and when I click OK, the application is not started?

Did you install java? You need at least version 1.6. You can download the latest version of Java here.

When I click on the application, all I get is some XML code?

Did you install java? You need at least version 1.6. You can download the latest version of Java here.

Can I use the application offline?

Yes, you can. Start the java control panel jcontrol and click View... in the pane Temporary Internet Files. A dialog opens with the cached java applications. On ISGCI, use the context menu under the right mouse button to run the application offline. Note that functionality that requires access to the ISGCI server will not work, e.g. filtering graphclasses or viewing class details.

Under unix, when I click 'help' or 'smallgraphs' or 'class details' in the app, nothing happens?

These menu items try to open a new browser window to display the requested information. If the app can't find the proper browser, nothing will happen.

Check in the Java control panel (jcontrol), tab Advanced, whether the Command to launch default browser is correct. If it is, but these menu items still do not work and your system uses the shared mime database, then you need to specify the default application for html files:

First find the .desktop file for your favourite browser, typically it will be in /usr/share/applications, e.g. /usr/share/applications/mozilla-firefox-3.5.desktop. Then edit the file ~/.local/share/applications/defaults.list, creating it first, if necessary. The first line of this file should be

[Default Applications]

At the bottom of the file add the line

text/html=mozilla-firefox-3.5.desktop

where the text after the equals sign = should be the name of the desktop file (without path) of your browser.

The database

I can't find inclusion A < B, class X, algorithm Y in ISGCI? There's a mistake in your database!

Please mail us!

Is there a way to get raw relationship data out of ISGCI, could I maybe get a copy of your database?

The easiest way to get relationship data out of ISGCI is to create a drawing of the classes that interest you (e.g. all subclasses of perfect graphs) and choose File/Export drawing. Then choose the GraphML format. This will export the classes and the relations between them as drawn, but without layout information.

Depending on your goals, this may not be enough. Maybe you would be served better with the XML file containing the relations, or with an online query possibility. Principally such solutions are possible, but we would need to know what you're trying to achieve, so we can decide on the best way to help you. For example, the Sage mathematics system contains such a copy of the ISGCI database (sage.graphs.isgci), which you can investigate with the full power of Python at your disposal. Note that this database may not be fully up to date in comparison to www.graphclasses.org.

Is it possible to have simple graphs available in adjacency list or matrix representation?

Yes, it is. The smallgraphs have next to their name a string preceded by g6:. This string is the graph6 encoding of the graph. The graph6 format can be read by e.g. sage and mathematica, which you can use to do all sorts of nice calculations on the graph. If all you want is an adjacency list or matrix representation of the graph, you can use the showg program.

I published an article with results that would fit right into your database. Can I send it to you?

Yes you can. The rules for adding data to ISGCI are simple: First, we must believe the result. This means it's published in a refereed journal or conference, or be so short that we can verify it ourselves. Second, it must fit in. Roughly speaking, this means that the classes described are of the type studied in algorithmic graph theory. If your article describes relations between your new class and classes that exist already in ISGCI, it should fit right in.

If your article describes a new algorithm for a problem that is already in ISGCI, it will probably fit in. If the algorithm is for a problem that is not yet in ISGCI, we still appreciate to hear of it, but we will put it on our "to do" list, until we have gathered enough algorithms to add a new problem.

We don't judge whether articles are "important" or "interesting". When in doubt, just send us your article.

Database contents

1600classes
217586inclusions
26190complexities
46905bounds

updated 2016-07-07


Latest news

  • 2015-03-26 Added support for graph parameters.
  • 2014-03-15 Add preview tooltips for references.
  • 2013-12-19 Bug fixed that prevented the application from running.