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This page explains the basic '''annotation''' features for [http://meta.wikimedia.org/wiki/Semantic_MediaWiki Semantic MediaWiki]. Annotations are special markup-elements which allow users to make some parts of the directory's content explicit so that software tools can use them to assist other users. In particular, semantic annotations provide the basis for more powerful [[Centiare:Searching|search functions]] within the directory. They also allow changes in data on one page to automatically propagate to other pages containing the same data (somewhat comparable with what can be done with [[Centiare:Template namespace|template]]s). Users who are not familiar with the basics of editing MediaWiki should first read the [[Centiare:Cheatsheet|Cheatsheet]].

 

This page explains the basic annotation features for [http://meta.wikimedia.org/wiki/Semantic_MediaWiki Semantic MediaWiki]. Annotations are special mark-up elements which allow users to label some parts of the directory's content, so that software tools can use them to assist other users. The annotations also allow changes in data on one page to automatically propagate to other pages containing the same data (somewhat comparable with what can be done with [[Centiare:Template namespace|template]]s). Users who are not familiar with the basics of editing MediaWiki should first read the [[Centiare:Cheatsheet|Cheatsheet]].

Annotations in Semantic MediaWiki can be viewed as an extension of the existing system of [[Centiare:Categorization|categories]] in [[Directory:MediaWiki|MediaWiki]]. Categories are a means to ''classify'' articles according to certain criteria. For example, by adding <nowiki>[[Category:Cities]]</nowiki> to an article, the page is ''tagged'' as describing a city. Software tools can use this information to generate an ordered list of all cities in a wiki, and thus help users to browse the information.  

Annotations in Semantic MediaWiki can be viewed as an extension of the existing system of [[Centiare:Categorization|categories]] in [[Directory:MediaWiki|MediaWiki]]. Categories are a means to ''classify'' articles according to certain criteria. For example, by adding <nowiki>[[Category:Cities]]</nowiki> to an article, the page is ''tagged'' as describing a city. Software tools can use this information to generate an ordered list of all cities in a wiki, and thus help users to browse the information.  

Semantic MediaWiki uses the category information, but provides further means of structuring the wiki:

Semantic MediaWiki uses the Category information, but provides further (we think ''better'') means of structuring the wiki:

 

* '''Attributes''' allow users to assign further information to an article by specifying ''data values'' for certain characteristic features. For example, [[Berlin]] could be associated with a ''population'' of 3,396,990.

* '''Attributes''' allow users to assign further information to an article by specifying ''data values'' for certain characteristic features. For example, [[Berlin]] could be associated with a ''population'' of 3,396,990.

Although these additions enable users to go beyond mere categorisation of articles, the usage and possible problems with using these features are very similiar to the existing category system. Since categories, relations, and attributes merely emphasize a particular part of an article's content, they are often called ''(semantic) annotations''. Information that was provided in an article anyway, e.g. that Berlin is the capital of Germany, is now provided in a formal way accessible for software tools.

Since Categories, Relations, and Attributes merely emphasize a particular part of an article's content, they are often called ''(semantic) annotations''. Information that was provided in an article anyway, for example, that '''Berlin is the capital of Germany''', is now provided in a formal way accessible to software tools like the [[Centiare:ASK|Centiare ASK]] code.

== Categories ==

== Categories ==

The main reference for the use of categories is the [http://meta.wikimedia.org/wiki/Help:Category MediaWiki documentation on categories]. Categories are used as universal "tags" for articles, describing that the article belongs to a certain group of articles. To add an article to a category "Example category", just write

The main reference for the use of Categories is the [http://meta.wikimedia.org/wiki/Help:Category MediaWiki documentation on categories]. Categories are used as universal "tags" for articles, describing that the article belongs to a certain group of articles. To add an article to a category "Example category", just write

  <nowiki>[[Category:Example category]]</nowiki>

  <nowiki>[[Category:Example category]]</nowiki>

to the end of the article. The name of the category (here: "Example category") is arbitrary, but of course you should try to use categories that already exist instead of creating new ones. Every category has an own article, which can be linked to by writing <nowiki>[[:Category:Example category]]</nowiki>. The category's article can be empty, but it is strongly recommended to add a description that explains which articles should go into the category.

preferably toward the end of the article. The name of the category (here: "Example category") is arbitrary, but of course you should try to use categories that already exist instead of creating new ones. Every category has its own article, which can be linked to by writing <nowiki>[[:Category:Example category]]</nowiki>. The category's article text can be empty, but it is strongly recommended to add a description that explains which articles should go into the category.

Categories can have many different interpretations. For example, the category "City" might comprise of all articles about cities, i.e. it describes that something is a city. Other categories, such as the category "Mathematics," might rather describe the topic area of an article. Many other interpretations exist. Semantic MediaWiki endorses this practical usage of categories: categories should be used to describe collections of articles that are considered useful or interesting for users. However, the advanced search functions of Semantic MediaWiki may make some categories superfluous, so that an SMW-enabled wiki might achieve a high degree of organization with far less categories.

Categories can have many different interpretations. For example, the category "City" might comprise of all articles about cities, i.e. it describes that something is a city. Other categories, such as the category "Mathematics," might rather describe the topic area of an article. Many other interpretations exist. Semantic MediaWiki endorses this practical usage of categories: categories should be used to describe collections of articles that are considered useful or interesting for users. However, the advanced search functions of Semantic MediaWiki may make some categories superfluous, so that a wiki enabled with Semantic MediaWiki (like Centiare is!) might achieve a very high degree of organization with far fewer categories.  Instead, learn to use Attributes and Relations.

== Relations ==

== Relations ==