Introduction to Semantic MediaWiki
Semantic MediaWiki (SMW) is an extension of MediaWiki – the wiki application best known for powering Wikipedia – that helps to search, organise, tag, browse, evaluate, and share the wiki's content. While traditional wikis contain only text which computers can neither understand nor evaluate, SMW adds semantic annotations that allow a wiki to function as a collaborative database. Semantic MediaWiki was first released in 2005, and currently has over ten developers, and is in use on hundreds of sites. In addition, a large number of related extensions have been created that extend the ability to edit, display and browse through the data stored by SMW: the term "Semantic MediaWiki" is sometimes used to refer to this entire family of extensions.
Why Semantic MediaWiki?
Wikis are a great tool for collecting and sharing knowledge in communities and organizations. This knowledge is mostly contained within texts and multimedia files, and is thus easily accessible for human readers. But though wikis are very good for storing and retrieving individual facts, they are less useful for getting queried or aggregated information. As a simple example, let's say you use a wiki that stores information about projects related to your organization. You have the following simple question:
- "What are the active projects that were started in 2012?"
This should be an easy question to answer, but in fact it's not - you would have to read through all of the pages about projects every time you wanted to answer the question. Text searches won't necessarily help. Categories could help to some extent, although they're not an ideal tool and maintaining them can become complex (see below). And there doesn't exist an artificial intelligence tool that could help with this task either.
Semantic MediaWiki enables wikis to make their knowledge computer-processable, so that you can find and display the answer to this question - and to many more.
Where SMW can help
Semantic MediaWiki introduces some additional markup into the wiki-text which allows users to add "semantic annotations" to the wiki. While this at first appears to make things more complex, it can also greatly simplify the structure of the wiki, help users to find more information in less time, and improve the overall quality and consistency of the wiki. Here are some of the benefits of using SMW:
- Automatically-generated lists. Lists and tables are a natural way to view information at a glance. In some cases, non-semantic wikis contain human-generated lists; Wikipedia itself has thousands, like "List of metropolitan areas in Spain by population". These lists are prone to errors, since they have to be updated manually. Furthermore, the number of potentially interesting lists is huge, and it is impossible to provide all of them in acceptable quality. In SMW, lists are generated automatically like this. They are always up-to-date and can easily be customised to obtain further information.
- Visual display of information. The various display formats defined by additional extensions, such as Extension "Semantic Result Formats" and Maps (formerly Semantic Maps), allow for displaying of information in calendars, timelines, graphs and maps, among others, providing a much richer view of the data than simple lists and tables would.
- Improved data structure. MediaWiki wikis tend to make heavy use of categories for structuring data. While these are generally helpful, consider the category on Wikipedia called "1620s births"; if the information in these pages were stored using SMW, these categories could be replaced by simple semantic values, reducing the need for a complex classification system. In addition, if semantic markup within the wiki is stored within templates, otherwise known as Semantic templates, a wiki can easily gain a solid data structure. And the Page Forms (formerly Semantic Forms) extension lets administrators create forms for adding and editing the data within semantic templates, thus making the addition of semantic information even easier and more straightforward than using regular wiki text.
- Searching information. Individual users can search for specific information by creating their own queries, supported via extensions like Semantic Drilldown and Page Forms (formerly Semantic Forms).
- External reuse. Data, once it is created in an SMW wiki, does not have to remain within the wiki; it can easily be exported via formats like CSV and JSON. This enables an SMW wiki to serve as a data source for other applications, or, in the case of enterprise usages, to take over the role that a relational database would normally play. Through the use of the External Data extension, SPARQL, and other tools, one SMW-based wiki can even use the data from another, eliminating the need for redundancy between wikis. You can also query SMW's data from outside the wiki, via the API or an RDF triplestore.
- Integrate and mash-up data. Data contained in an SMW installation does not have to be an isolated store of information. Extensions such as Data Transfer and External Data empower you to integrate external data (coming e.g. from legacy systems, web services or linked data sources) and interrelate it with existing semantic data in the wiki. Thus, an SMW-powered wiki can serve as a central information hub in an IT landscape.
Who is using Semantic MediaWiki?
Semantic MediaWiki has grown a long way from its roots as an academic research project. It is currently in active use in hundreds of sites, in many languages, around the world, including Fortune 500 companies, biomedical projects, government agencies and consumer directories. The Wikipedia article on Semantic MediaWiki contains a section listing some of its notable users. You can also see a more comprehensive list of sites that use SMW here. It should be noted that both lists focus on public sites, although perhaps half or more of the sites that use Semantic MediaWiki are private, for internal use by companies and organizations.
There are a growing number of consulting companies that implement SMW as part of their solutions, with some stating their use of MediaWiki and SMW explicitly and others keeping it as a hidden implementation detail. (You can see a listing of people and companies that can be hired to do SMW-based work at the "professional support" page.)
Websites that currently offer hosting services for Semantic MediaWiki and some of its extensions are listed in wiki farm provider.
You can read about positive experiences using SMW among companies, organizations and individuals at the testimonials page.
This site has much more information about setting up and running a Semantic MediaWiki installation. The Administrator manual holds information on downloading, installing and troubleshooting SMW; and also has information on the various extensions that can be installed to work together with SMW. The User manual holds information on defining properties, running queries, browsing data and the like. And the FAQ has answers to frequently-asked questions on both technical and non-technical issues.
Contact and user support
For contacting the SMW Project, see the contact page. For comments and questions, there is an active user mailing list that you can join, as well as an IRC Channel, #semantic-mediawiki. See Help:Getting support for further information about support for SMW.