Netscape Restores RSS DTD, Until July

Randall Bennett writes "RSS 0.91's DTD has been restored to it's rightful location on my.netscape.com, but it'll only stay there till July 1st, 2007. Then, Netscape will remove the DTD, which is loaded four million times each day. Devs, start your caching engines."

Re:mirror ;)

[geoffspear]

Great, the entire internet community can rely on one random person's server instead of on one really big corporation's server. That should fix things.

Re:I don't get it

[jrumney]

Developers use off the shelf XML parsers, which generally take care of validation for you. Netscape created this problem themselves when they stated in the spec for RSS 0.91 that well-formedness was not enough, RSS 0.91 feeds should be validated against the DTD. They then specified that document authors must use a PUBLIC doctype specifier, so the option of using a SYSTEM one (where the DTD is looked up in a local catalog) is not an option.

"Caching" not the answer

[KrisWithAK]

As I replied for the previous Netscape RSS DTD article http://slashdot.org/comments.pl?sid=216818&cid=176 03480 [slashdot.org], caching DTDs from the network is not the answer if there is the possibility they will not be there in the future:

The proper thing to do is for your application to use an XML catalog for resolving entities/URIs and bundle the DTD files with the application. There is a good article at http://xml.apache.org/commons/components/resolver/ resolver-article.html [apache.org] that helped me out. In addition, if you are using Eclipse with the web tools platform, you can customize the catalog so it resolves DTDs and entities locally. See http://wiki.eclipse.org/index.php/Using_the_XML_Ca talog [eclipse.org].

Re:Redirect

[AndroidCat]

I didn't say that it was Microsoft's fault. It's just that it's a powerful tool with thousands of uses that's simple (on the surface) to use, but it pays to read the fine print carefully because many things aren't obvious. (/me remembers wasting time wondering why my XPath queries weren't working...)

Re:Spelling issue

[JasonKChapman]

What's so fucking hard about spelling "its" correctly?

An old Jedi mind trick:

Its apostrophe is missing, because it's been moved over here.

Re:Its

[Anonymous Coward]

I think you should subscribe to this newsgroup [google.com].

Re:Why can't we just move it?

[metamatic]

You know, if you're gonna be a smartass on this topic, you should at least understand the difference between a URI and a URL.

There's nothing flawed about the notion of a permanent URI. A permanent URL is the tricky bit.

Re:pi meter

[Anonymous Coward]

pi = any circle's circumference / diameter. At least on a Euclidean plane, anyway. It's a bit incorrect to think that the value of pi varies, as it's defined in a particular type of geometry. There are also purely mathematical ways to define the value of pi, independent of geometry. Still, the idea of measuring space to get the value of "pi" is a valid way to think about measuring the curvature of space.

Now, let's say space is curved, like a sphere. (Like, oh, the one we live on.) If you draw a circle, say, the circumference of the Earth (along the equator), and then try to measure the "diameter" on the sphere (over one of the poles), you'll find it's much larger than the actual diameter (straight through the planet's core), and hence the "value of pi" will be much different. (In fact, it'll be 2, give or take a few decimal places since the Earth isn't a perfect sphere.)

To create a "pi meter", you might think of a device consisting of a fiber optic loop, like in a laser ring gyro; you simply measure the amount of time it takes for light to go around to measure the circumference of the loop, as well as using another pulse to measure its diameter. If space curves (as indeed it does, although not in any way that's noticeable far from, say, a black hole), you'll find a discrepency between your measurement of circumference / diameter and the defined value of pi.

You could also do the same thing with a piece of string and a ruler, but it wouldn't be convenient enough to call it a "pi meter".

URLs, URIs and URNs 101

[metamatic]

URLs are a subset of URIs. A URL defines a location where a resource can be accessed. A URI may merely be the name of a resource, i.e. a URN.

For example, globally unique IDs in Atom feeds are often URNs, and hence URIs; but URNs aren't URLs, and you shouldn't need or want to try to connect to something just because it's used as a globally unique identifier in an Atom feed and looks a bit like a URL.

This is relevant because many Internet specifications use URNs (or in the case of HTML, FPIs) as spec identifiers. For instance, XML namespace identifiers are URIs; and while some of them happen to be URLs too, the XML namespace recommendation [w3.org] says:

The namespace name, to serve its intended purpose, should have the characteristics of uniqueness and persistence. It is not a goal that it be directly usable for retrieval of a schema (if any exists).

In the case of RSS 0.91, Netscape wrote the spec, and they used a URL and told people to connect to it to fetch the necessary information to parse the file. They could have used a URN, but I'm guessing they wanted to keep their options open as far as changing the spec on the fly.

(Of course, Dave Winer has a different approach to changing RSS specs on the fly...)

Re:URIs

[Schraegstrichpunkt]

No. This is the perfect example of why a URI is not necessarily supposed to be treated as a URL. http://my.netscape.com/publish/formats/rss-0.91.dt d is just a unique identifier for the RSS DTD. It used to also be hosted there as a convenience, but your software isn't supposed to rely on that.