Can someone PLEASE explain XML (eXtensible Markup Language) to me???

[Superwormy]

All I basically want to know is what is its true purpose? What problems does it fix? Why's it here to stay?

The only things I can find online all sound like a bunch of propaganda... not actual useful information / explanation of what it is...


From what I've read so far, it seems like XML is a standard which tries to establish a standard way to store data. So almost like a database, but a database which uses one standard format to store the data no matter what application is reading / writing it. So almost like if PostgreSQL could read MySQL and msSQL database formats and vice-versa... yes?


What is so amazing about XML to make me want to learn it, and integrate it into web applications? Hell... HOW would you intergrate it into a web application...? Whynot just use a database instead?

Educate me please!

 

[sep]

I don't now exactly, but I'm attempting to learn it for the sake of the skill set. Here is a link that might help you (you might already know about this site).

W3SCHOOLS

Also, if you find an answer to this question let me know!
-JC

 

[Moonbender]

Just to give an example where XML is useful, many sites offer an XML file containing information about them, such as news headlines or more site-specific stuff. Blue's News, for instance, has an RDF describing the current news. This gives other sites or services an easy way to display or otherwise process Blue's News without accessing BN's backend server.
XML can be similar to relational databases such as MySQL, but it's both more dynamic - you don't necessarily have the same structure over and over, you'd have a hard time putting an XHTML document tree into a relational DB. Of course, databases are better at other things, they're way more efficient than programs processing XML are, for instance. It's apples and oranges really, both fruits, but not the same.
XML can also be an intermediary step, between the database abstraction layer and the final document output. This is a way to not only seperate content from layout, but content source (eg. a DB), content, and layout. One script could pull the data from a database and create an XML file, another script or program on perhabs a completely different computer could pull the XML file and create an (X)HTML representation, or a PDF file or whatever.

Whether it's terribly useful in the real world, and especially if it's well suited for what it's supposed to do is a topic for religious wars.

 

[Superwormy]

Interesting... anyone else have any thoughts on this?

I'd especially like to see some real-world examples... it seems like the most useful aspects of it are sharing data between websites, or maybe between a ring / set of websites. That I can see would be immensly helpful in many cases.

After reading som emore, it seems like XML is only a little bit useful in the real world.


Also, anybody have any thoughts on XHTML? XHTML really seems like it should have been implemented a LOOONNNG time ago, seems like it really tries to establish an HTML standard that works and would display consistently across platforms / browsers.

 

[geoff2k]

There was an interesting XML-related quote I read in eWeek recently:

The text-based protocols used by Web services typically require 10 times the bytes of a binary protocol to send the same information and have to be transformed at both ends into binary form, a relatively slow and CPU-intensive process.

That's the part that always gets me. Yes, its great for interop, but does nobody care about performance?