Compatibility | Security | Usage | Tutorials | Limitations
This is one possible form of a data browser. It is only one way of looking at the semantic web, just as a refrigerator is just one way of using electricity.
The tabulator is currently highly platform-dependent. See below for details
Firefox: All features tested in FireFox. To view sites outside of the local domain, you must change your FireFox settings.
Opera: The implementation works pretty well, although it's not yet completely debugged. There is currently no way to access sites outside of the local domain. To resolve this problem, a widget has been developed.
Safari: Weird bugs occur all over the place. "Undefined" is littered all over the screen.
Internet Explorer: Not functional in Internet Explorer. We are working on this.
Firefox security won't in general let a script from a given DNS domain (like www.w3.org) read web data from a different domain. Therefore, if you try to browse an rdf file from a different domain, the tabulator will fail. There are two ways to allow cross-domain requests.
Note that this is reducing the security of your browser. You end up allowing any web page on the site to read data from the web, which could include data from inside your firewall.
Quit Firefox and then find your prefs.js file and add to the bottom of it the line
On Mac OS-X the file will be in somewhere like /Users/timbl/Library/Application Support/Firefox/Profiles/mxotp788.default, and in Windows in an equivalent place. Then, run Firefox and the tabulator again, and answer the dialog box as above.)
The tabulator program is acting as your agent as you browse data, but the Firefox program doesn't know that you can trust it. It could be just a script on some webpage you are browsing, and it could be trying to get information which only you have access to and send it to a third party. It turns out that it is really difficult to stop such a script sending messages out in some form, so Firefox security prevents it from accessing anything on the web to which you have access to, unless it on the same DNS domain as the script itself. This is not a very good system, as many web sites which do not trust each other share a domain name. But that is how it is. A better way is for the scripts to be signed, but I haven't got the script signing system working yet.
See also Mozilla/Firefox documentation on See also Customizing and Signed scripts.
While you are adjusting the Firefox parameters, you may wish to increase the dom.max_script_run_time value in about:config. The default seems to be 5 (whcih seems to give in practice around 10 secs) of time in between Firefox asking whether it is Ok whether the script is still running. This happens when loading large RDF files. Try 30 or adjust to taste.
The outliner window allows you to explore the semantic web in a tree structure. The outliner begins with several initial rdf nodes (the objects with clickable symbols), and you can add more by around between different objects by adding their URI at the top of the window and clicking "Add to outliner". To explore an rdf node, simply expand it by clicking the icon for that node. You can click it again to collapse it.
The colored dot next to a given node indicates the status of retrieval for that URI. See the key above. Once a data source is retrieved, it will not need to be retrieved again, and the colored dot will not appear in future copies of that node. A list of data sources, accessible and not, is kept at the bottom of the browser.
Once you begin browsing, the nested tables quickly get quite deep. You can clean it all up, refocussing on one item by shift-clicking on its expand or collapse icon. This removes the nested tables, and places your selected node into the tabulator as a starting node.
Alternatively, if you would like to refocus on a node without removing the original tree you were browsing in, you can double-click on a node field (the text next to a / icon).
The point a browser is to give you the data without the URIs used as identifiers. They are hidden whenever there is a label, title, or name of some sort which can be used for something on the screen.
To see something's URI, click once on a table cell and (if appropriate) the URI of the thing described in the cell will be put in the URI bar at the top.
As you explore the outliner, you may want to create a table with certain pieces of information about each of several equivalently-related objects. This is how to do it:
For example, to make a table of the names of all the W3C working group chairs and team contacts, expand World Wide Web Consortium -> W3C Groups and Organizational Structure -> working group. Now, you may want to shift-click the "working group" icon to refocus it. Open up one of the working groups and click on the "chair" name field. Now alt click on the "team contact" field. Both these fields should now be highlighted in green. Now you can go down to the bottom of the tabulator and click "Tabulate selected properties" to create the table.
What you will notice in this example is that every combination of working group/chair/team contact has its own entry in the table. You can sort the table by clicking on the column heading of the column to sort by. Click again to sort in the opposite order.
This bit is very much work in progress just now!!
If you take the URI of the tabulator page, and then append uri= and the uri-encoded URI of the thing you are viewing, then this is a URI of a tabulator view for that thing. You can get the URI for anything in the tabulator outline view by clicking on it, and then looking in the tabulator's URI form field (not the browser's address bar). Remmeber to encode # as %23.
This is a proof of concept program, many user interface things are missing, for example from the table view.