One student has asked if I could upload Monday’s lecture, rather than just the tutorial. Here’s the manuscript, then. The slides are available in OOo and Powerpoint format.

Colophon: the slides are set in ITC Officina and make extensive use of the open-source Tango icon library. Hands: Gallaudet Regular. Hat: House of Lime. Special appearance as Bunny Rabbit by Sir John Tenniel‘s March Hare.

Both services have since become prettier to look at, but I’m not sure the markup validation service has improved a great deal in usability. The CSS validator has always been reliable and straightforward, which is lot more than could ever be said about the markup validator. It used to be a fair bet that wherever the validator pointed out an error, the actual mistake would be a few lines further up in the code from the line that was indicated. The error count used to be grotesquely inflated, too, as any given mistake in the code would spawn an unpredictable number of knock-on validation errors. I haven’t been using the validator a great deal recently, so I can’t really judge its current performance, but the inflated error count still appears to be a problem.

On the up side, though, I did discover recently that the markup validator’s Validate by Direct Input feature will also evaluate Scalable Vector Graphics, which proved handy the other day when I needed to fix a broken piece of vector art.

It’d still be nice if the validator could reliably point to coding glitches instead of requiring all that extra effort interpreting its output.

Radial graph

digraph G {

"a" -> "b";
"a" -> "c";
"a" -> "d";
"a" -> "e";
"a" -> "f";
"a" -> "g";
"a" -> "h";
"a" -> "2";
"a" -> "3";
"a" -> "4";
"a" -> "5";
"a" -> "6";
"a" -> "7";
"a" -> "8";
"a" -> "9";
"a" -> "10";
"a" -> "11";
"a" -> "12";
"a" -> "13";
"a" -> "14";
"a" -> "15";
"a" -> "16";
"a" -> "17";
"a" -> "18";
"a" -> "19";
"a" -> "20";
"a" -> "21";
"a" -> "22";
"a" -> "23";
"a" -> "24";
"a" -> "25";
"a" -> "26";
"a" -> "27";
}

Rendered with: $ twopi -Tpng sample116.dot -o sample116.png

This works quite well with just a handful of nodes, but with node numbers in the dozens and hundreds, edge length for the outer nodes increases dramatically. There doesn’t seem to be a way to pack this sort of graph tightly for lots of nodes.

Judging by the 11,000 bookmarks on Del.cio.us and the 3,000 diggs on Digg, the brand-new bitmap-to-vector service from Stanford got off to a good start. The professionals are impressed, too.

Me? I’ve done some auto-tracing in Inkscape, which does a good enough job for my needs. Still, I’ve just put a number of graphics through Vector Magic that I had sitting around from many years ago: ink-on paper line art of mine that I scanned and reduced to aliased gifs way back in time. Vector Magic did really well on them. Here’s a side by side comparison.

View the complete slide show, have fun with open-source icons.

Surprisingly, Google Trends reports that Joomla has had a higher search volume than WordPress since mid-2005. It still beats Web 2.0 though, but loses to Paris Hilton.

—-
[1] This map was presented by Tim Berners-Lee as part of his Short History of the WWW, delivered in October 2007.

This isn’t going to become permanent, but a similar project might get going soon…

The other day I went to an electronics store and looked at external hard drives: why not copy the whole lot onto a portable drive and be done with it?

While discussing the issue with a computer scientist, we got to talk about network backups. I asked him to explain why he liked the idea so much. And he did:

Just before I learned about StrongSpace I was thinking that such a system needed to exist. The reason is that there are some problems with backups:

1. People forget to do them or don’t bother because they are inconvenient.
2. If they are located in the same machine as the original data they are not protected from catastrophes (e.g. fire).
3. Making a backup means you have another copy of your data floating around, which means others could steal that data and see all your naked people pictures and health records and stuff.

Offsite backups (to a file server someplace) solve some of these problems. You use a script that is run every so often, and it magically uploads your stuff to some network storage space. However, transmitting data over the internet means that it is inherently less secure: people could sniff the packets as you transmit them, and the network admins running your internet storage can see what your files are. Ethically, they should not care, but I do know that sysadmins snoop. Plus if the police come asking for your data the sysadmins have to provide it. From a security standpoint you would prefer that the sysadmins are unable to see what is going on.

Strongspace almost solves the entire problem. It provides a connection that is probably secure for your data, and it provides lots of space. If your office catches fire you can still get your data, and if the StrongSpace servers catch fire then you have the data in your office. That is good.

The only weakness is that the sysadmins can still snoop on your files. There are ways around this (encrypted or doubly-encrypted filesystems, or just encrypting your tarballs before sending anything), but StrongSpace does not make that easy.

Network backups are the wave of the future. StrongSpace excited me because I knew of nobody else that realized this enough to offer committed hosting for backups.

Keeping the stuff online would have its benefits, too, because it would remain accessible from anywhere. But then most of the stuff won’t need to be accessible from anywhere because I probably won’t ever look at it again. Maybe I don’t need to catch the wave of the future just yet, so, after all, I’ll buy an external drive for stashing it away offline. We’ll see.