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>>So it's a bit like Adobe pdf. files?
No. XML (Extensible Markup Language) is used in the creation of Web sites and tags for posting to the Web. As Yewanchors states in great detail, it's a successor to HTML (Hypertext Markup Language).
XML is not the successor to HTML, but they have a common heritage in SGML. The HTML specification was also rewritten in XML, mostly as a proof of concept sort of thing, but it's known as XHTML.
But XML is aimed more at creating your own HTML-like languages for programs. From a programming standpoint, XML is a fast and flexible way to wrap legacy data, create a communication bridge between two systems, or store configuration settings, among other things.
Just because XML and HTML look a lot alike, doesn't mean they are anything alike. XML has been used to craft MathML, a language for displaying complex mathmatical formulas on web pages, VRML has been redone in XML, SVG is XML based and it's something of a Flash replacement, there's a markup language for modeling chemical formulas and all manner of things inbetween. In a project I'm working on, I'm using it as a sort of flat database to store client data until such time that a real database becomes warranted. Microsoft uses an XML based language for saving all Office documents since I think Office 2000 (maybe OfficeXP).
There's simplifying things, and then there's misrepresenting things. Your comments are more towards the latter, whether that was intentional or not.
I am a chemical engineer by profeesion .. I wanted to know if Chemiccal Mark up language is the same as XML . If there was a site purely meant for CML or where I could download info ..p[lz lemme know
It's a series of rules that allows you to create markup tags in a document to describe different parts. If you've ever seen HTML "code" then you've got a fair idea of what XML is, only XML is much more flexible. XML and HTML actually have a common parent in a much larger and complex markup system known as SGML. Recently HTML was "rewritten" in XML to create HTML. Which basically is just a somewhat "cleaner" version of itself.
Essentially, XML allows you to insert HTML-like tags into any document which will have some sort of significance to a program that uses it. Just like HTML tags have significance to the web browser. The different tags tell the web browser how to display the page. XML just expands the scope to pretty much anything, not just use in a web browser.
For the most part, XML is only something of interest to program developers. It can make for a very programmer friendly way of creating fast and flexible configuration files, as well as storing any data that the program might need to save. As far as the average computer user is concerned, it's just another ackronym that we computing professionals are so enamoured with. You don't really need to worry about it, because it's use should be completely transparent to you.
But if you really want to learn more than you ever wanted to about XML, pick up a copy of "Learning XML 2nd Edition" by O'Reilly Publishing. Fair warning, it's not exactly an action packed spy thriller type novel. It's really kind of dry and boring, but it does cover pretty much the A-Z of XML.
I'm hardly an expert, but I can share what I know.
XML (Extensible Markup Language) is similar to HTML (HyperText Markup Language). It's a set of codes that work together to display the content (text and graphics) on a website page. By the way, both of these languages trace their ancestry to SGML (Standard Generalized Markup Language).
Before I jump into XML, here's a brief review of how HTML works. HTML consists of codes that are standardized by the World Wide Web Consortium (W3C). To slightly oversimply things, your browser is programmed to interpret HTML codes in a website page to display the page contents accordingly. If all browser developers designed their browsers to understand only the currently standardized HTML codes, all browsers would work the same. However, the browser developers each push the edge a bit, and invent new HTML codes, programming their browser to understand their new unstandardized HTML codes. Website developers, eager for more flexibility, jump on board and start using these unofficial codes. This creates the browser incompatibility because when a website page uses non-standard HTML codes, only one type of browser will interpret them correctly. The W3C then reviews new HTML commands put into service by the browser developers, and some of them get added to the official list. So HTML grows and expands its repertoire as developers create, push the edge, and the W3C reacts. This is a slow process and creates interim confusion for web users (and some really ugly websites).
XML, on the other hand, allows for both standard codes and customized codes created and defined by an XML coder/user for a specific purpose. New codes can be defined on the fly and understood by browsers/viewers. This means that XML has much more flexibility and doesn't suffer from browser incompatibility. You might think of XML as HTML on steriods, or (in this more steriod-aware sports era), you might think of HTML as Clark Kent and XML as Superman.
I'm a technical writer, and I've been using HTML since about 1995. Over the last few years, my work has changed to almost exclusively use XML instead. I'm not the only person who has seen this trend. HTML is being replaced by XHTML (Extensible HyperText Markup Language) which is currently being defined by the W3C as a bridge from HTML towards XML.
For more technical information, I recommend that you read the W3C's XML page at: http://www.w3.org/XML/
First of all, XML is NOT HTML.
Syntactically, HTML and XML are nearly identical since they are both based on Standards Generalized Markup Language; one main difference is that XML has more strict rules (all tags must be closed, attributes can not be collapsed). But while HTML is used for a single, specific purpose (to describe web pages), XML can be used to describe any kind of data, depending on how the application uses it. In one sense, XML is a framework for building other markup languages.
Many XML-based languages have been developed to describe various kinds of data. OpenOffice.org encodes it documents in XML files (which are actually later compressed into ZIP files). RSS is used for news syndication among Internet sites (orange 'XML' buttons on PostNuke sites, etc.). eXtensible User interface Language provides the powerful, modular GUI used by the Mozilla browser. SVG (scalable vector graphics) is a standard for displaying scalable images on the web. XHTML is a replacement for HTML which is implemented in XML. Jabber is an instant messaging protocol that sends data between clients and servers in little bits of XML.
From a programming standpoint, XML provides a simple interface for applications to access data. The same XML "parser" library can be used by a news aggregator, web browser, or anything. The parser need not care what on earth the data describes, and the application developer doesn't have to worry about deconstructing the file's syntax or character encoding.
XML is a simple but powerful technology with an infinite number of uses, and it will have even more in the future. You probably use it on a day-to-day basis, at least indirectly, in many more ways than you know.
XML stands for eXtensible Markup Language. It is a cousin of HTML in that they are both "markup languages". That is a term that originated in early word processors when you had to "markup" text to format it. (For example, using a "tag" such as <BOLD> for bold face type.)
HTML is used to mark up text for display. XML is used to mark up data for data exchange so that data can be interchanged between systems without having to worry about the destination system. (Much like HTML lets you mark up text for display without having to worry about what operating system and platform will be doing the display at the other end.
Hope that helps.
Well, let me answer this from a slightly different angle.
In essence, XML is a language that allows COMPUTER to understand the content of the data being transmitted. (versus HTML that helps HUMAN to understand the content by formatting the data in pretty format).
Technically, XML allows data to be marked up with the description of what the data is about (ie, customer_name), as well as allowing a more advance data structure (ie an invoice with invoice details) to be transmitted. This in turn allows computers (applications) to talk better with other computers.
Add to this a whole slew of XML standard (such as ACCORD for insurance industry) that describes what data is needed for a particular industry. What this means to business is that industrial strength solutions has a better chance of working (out of the box) with each other. Thus lowering the cost of IT technology acquisition and bringing business partners closer together (at least IT-wise).
This is NOT a new concept. various industry standard has existed before. But industry has never taken it up like this before.
The down side... Well, XML parsing is SLOOOOOOWWWW. Why in the world would the most successful language that allow data to be transmitted between computer applications be written in ASCII/text is one of those cosmic accident that will haunt the IT industry much like the cause of the Y2K bug.
Hope this helps...