What is XML?

Information

Information can be stored in many ways. You can take a word document and write up a list of things to do, and save it somewhere. The next time you might save some information about a recipe in another word document. Structuring that information becomes difficult if you increase the amount of recipes and lists, and also wish to categorize them somehow.

Within XML it is very easy to describe the information so that you know what is what. For example a title can be described as

<title>What is XML?</title>

Describing larger chunks of information, for example an entire recipe with a title, text about the preparation, a list of ingredients and other necessities, can be done by placing smaller 'tags', such as the title, in larger tags. This is called 'nesting'. A title tag is then nested in a recipe tag.

<recipe>
	<title>What is XML?</title>
<recipe>

A category tag could thus be added, and one could go on forever. This is structuring information. Multiple recipes can be nested under a category.

XML

XML is structured information. People can make up their own structures, but in order to make information usable and accesible to a lot of different systems there are also standards for XML so that those systems know what to expect. For example you could understand how having more that one title in a document could be confusing, unless the titles have a language attribute to show that they are different.

XML isn't a very legible interface for editing information though. It is good for describing the information, but it is difficult to edit a document where the actual information is surrounded by tags. In a word processor you can easily just type up your information, make a list or a header, and work on layout.

Nowadays there are many systems that can use XML to fill up a layout and then display it, or print it. In XML it is clear what is a title, and what is a list, and so if you were to provide the layout, the system can put your information in it. Using XML for saving information is thus becoming more and more popular. Not only does XML make information easier to understand (imagine a recipe in another language, but still in English tags), but it also allows more people to use it.

The use of XML

Because the information is structured, and perhaps standardized, it can be used by many different people and systems. Anyone can make a layout for a recipe in any langauge, if the markup, the XML, of that recipe is in English. You can see what is the title, and you don't need to know what it means.

XML can be used almost everywhere. It is used online, for printing purposes, even in interfaces, mobile phones, and it makes for a very custimizable data-format, so that everyone can change things.

Xopus and XML

Editing XML is still a problem. Nowadays people either have a very simple structure and the editing is easy and user-friendly, or people have a complex structure, but it is near impossible to edit it, because the system can't show it in a user friendly way.

Xopus uses Schema, which is a standard for describing XML. Schema describes what is possible, impossible and required in an XML format. For example with a recipe comes a schema which describes that there can only be one title, one list of unlimited ingredients, and one section called description with any number of paragraphs. With Schema Xopus knows the structure of the XML that it is editing, and so allows, disallows, and requires people to do things with their XML. Xopus helps the user edit a complex structure while providing a user friendly view on that information. So you could never write a second title in your recipe. In a word document this would be possible, but it wouldn't make any sense.