My 5/03/09 Missoulian column
Writing about RSS and news feeds over the last few weeks got me thinking about XML.
The success of news feeds and other Internet services depends on XML, which is a fairly new computer language that was formalized for widespread use about 10 years ago. XML stands for extensible markup language – one of many languages that the Internet and Internet services rely on.
Before we figure out what “extensible” and “markup” mean, we have to talk about computer languages in general.
One of the fundamental differences I like to point out among the many computer languages in use is that some do things, while others describe things. Experts in computer language development and semantics might cringe at that simplistic difference, but I think it’s a helpful distinction to keep in mind.
In other words, some languages crunch numbers and work with algorithms, while others simply describe the structure of data or information for other languages to work with.
It’s a little like verbs and nouns: Verbs are actions and nouns are names of things. Some computer languages are like verbs, taking actions at the direction of a computer user. Others are like nouns, describing things and waiting for other languages to work with their data.
The languages that make up the software your PC runs on are verb-type languages, while the XML that provides the data of the news feed is a noun-type language.
XML is more commonly called a markup language. It’s used to describe things by marking them up, or putting bits of XML language around the data that is being described. And, as in any computer language, it has to work in a precise grammar, too, or chaos would result.
XML marks up data in a standard way for presentation to other computer languages. It doesn’t describe the presentation of data, what can be done with the data or how a PC should run. That’s up to other languages.
So, XML marks up the data of an RSS feed so the headlines, weather and product announcements are in a standard format for news readers. And XML marks up data so other languages and computers can access it in the same way, too.
The “extensible” part of XML is also important; that’s for next week.