Why learn XML?

I've been tasked to learn XML for work. A straightforward thing to have to do and I've already began working it out (the basics, of course).

Now, before I get right down to it, why should I learn XML?

From what I have seen, I need to drop data into an XML document (linked to a DTD for all the entities) and use that document full of data as a data-source for pages.

As I understand, a relational database will do the same job for me. My job at my employer is in PHP/Python and MySQL. Why should I use XML rather than MySQL.

For reference, I understand that I can pull data from XML files using PHP. But I can also do the same from MySQL.

I'm confused and need a good talking to. Please help me understand why I should be using XML.

Yours in faith,
estron

Here is one reason: Portability.

If you have a perfectly designed database and you are going to share the data with another company in a partnership, etc., then you can have a host of problems in dealing with compatability/conversion issues.

In the publishing industry, we often need to share data or sell raw data to another entity and xml, and markup languages in general, provide a good universal standard. I know that after passing along the data (say the whole text of a book or article) that the other person either (1) has the tools to use it or (2) can create them without significantly reconverting the data. Thus, the data as a product is worth more money.

I am sure others will have additional reasons.

Given what I have said above, every situation is different and deserves its own analysis.

The only reason you would need to use XML is if you plan to export data that will be used by multiple platforms. If all your data is to stay in PHP and never be transferred to any other platform or offsite location, then don't waste your time. XML is a big headache, and until they come out with some better standards it's a waste of time unless its necessary.

i'm php/mysql developer myself. the way i see it is: one file for all. with a single xml document you could have a txt, html (for screen, print and so on medias) and you can easily make pages for cells.
sounds great and works great.
that's how i see it and experience it