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==Who develops Semantic MediaWiki?==
==Who develops Semantic MediaWiki?==
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SMW was originally developed by several programmers at the [http://www.kit.edu/english/ Karlsruhe Institute of Technology] (KIT), although since then the effort has spread to include a number of other developers around the world (and the original developers have all left KIT). See [[Help:SMW Project]] more information on SMW's developers and development history. SMW-based extensions are developed by a large number of contributors, some
(but not all)
of whom have also contributed to core SMW.
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SMW was originally developed by several programmers at the [http://www.kit.edu/english/ Karlsruhe Institute of Technology] (KIT), although since then the effort has spread to include a number of other developers around the world (and the original developers have all left KIT). See [[Help:SMW Project]] more information on SMW's developers and development history. SMW-based extensions are developed by a large number of contributors, some of whom have also contributed to core SMW.
==How popular is it?==
==How popular is it?==
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SMW is currently in use on [http://smw.referata.com/wiki/Special:BrowseData/Sites?Status=Active
around 330
active public wikis]. It is impossible to know on how many private wikis it runs, but a rough guess, based on the frequency of public and private wikis asked about in bug reports and the like, is that it's used on about the same number of private wikis as public wikis.
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SMW is currently in use on [http://smw.referata.com/wiki/Special:BrowseData/Sites?Status=Active
over 300
active public wikis]. It is impossible to know on how many private wikis it runs, but a rough guess, based on the frequency of public and private wikis asked about in bug reports and the like, is that it's used on about the same number of private wikis as public wikis.
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Some of the better-known public wikis that use Semantic MediaWiki include [http://en.openei.org/wiki/Main_Page OpenEI]
and
[http://www.snpedia.com/index.php/SNPedia SNPedia]. Companies that use SMW internally include
Audi
and Pfizer. Other organizations that use SMW include NATO and the United Nations. SMW is also used by government agencies in various countries, including the United States, Canada and Austria.
+
Some of the better-known public wikis that use Semantic MediaWiki include [http://en.openei.org/wiki/Main_Page OpenEI]
,
[http://www.snpedia.com/index.php/SNPedia SNPedia
] and [http://docs.webplatform.org/wiki/Main_Page Web Platform Docs
]. Companies that use SMW internally include
Johnson & Johnson, Philips
and Pfizer. Other organizations that use SMW include NATO and the United Nations. SMW is also used by government agencies in various countries, including the United States, Canada and Austria.
==How is Semantic MediaWiki's performance?==
==How is Semantic MediaWiki's performance?==
There have been various tests done already to determine SMW's performance, in addition to fairly large-scale real SMW installations. Unfortunately, none of the findings of any of these tests have been published yet. However, we do know some of the conclusions: SMW has been used successfully even with millions of rows of data; and the limiting factor is usually overly-complex queries. Various standard performance improvements have been shown to have a helpful effect on SMW performance, including the use of caching tools like [[wp:en:List of PHP accelerators#Alternative PHP Cache .28APC.29|APC]] and [[wp:en:Memcached|memcached]], and MySQL adjustments like increasing the buffer size and using a separate database server. The page "[[Speeding up Semantic MediaWiki]]" includes more such tips.
There have been various tests done already to determine SMW's performance, in addition to fairly large-scale real SMW installations. Unfortunately, none of the findings of any of these tests have been published yet. However, we do know some of the conclusions: SMW has been used successfully even with millions of rows of data; and the limiting factor is usually overly-complex queries. Various standard performance improvements have been shown to have a helpful effect on SMW performance, including the use of caching tools like [[wp:en:List of PHP accelerators#Alternative PHP Cache .28APC.29|APC]] and [[wp:en:Memcached|memcached]], and MySQL adjustments like increasing the buffer size and using a separate database server. The page "[[Speeding up Semantic MediaWiki]]" includes more such tips.
−
Starting in
[[Semantic MediaWiki 1.8.0|version 1.8]], which was released in December 2012, SMW
is using
a new database structure, SQLStore3, which includes a variety of performance optimizations, meant to improve both the storage and querying of data.
+
In
[[Semantic MediaWiki 1.8.0|version 1.8]], which was released in December 2012, SMW
adopted
a new database structure, SQLStore3, which includes a variety of performance optimizations, meant to improve both the storage and querying of data.
==How does SMW store its data?==
==How does SMW store its data?==
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==Why doesn't data I have just added show up in queries?==
==Why doesn't data I have just added show up in queries?==
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There is sometimes a lag between when SMW data gets created or modified, and when that new data shows up in queries; that is due to MediaWiki's own page caching. Some people, not knowing any alternatives, get around this by re-saving the page containing the query, but this is not necessary — you can refresh the query just by doing a MediaWiki refresh/purge on the page. If you are a MediaWiki administrator, you can do this by simply hitting the "refresh" tab (not to be confused with the browser's "reload" button, which will not have any effect).
If you are not an administrator, going to the URL that ends with "&action=purge" for that page will have the same effect. Or you can simply wait — cached pages usually get refreshed within 24 hours or less.
+
There is sometimes a lag between when SMW data gets created or modified, and when that new data shows up in queries; that is due to MediaWiki's own page caching. Some people, not knowing any alternatives, get around this by re-saving the page containing the query, but this is not necessary — you can refresh the query just by doing a MediaWiki refresh/purge on the page. If you are a MediaWiki administrator, you can do this by simply hitting the "refresh" tab (not to be confused with the browser's "reload" button, which will not have any effect). If you are not an administrator, going to the URL that ends with "&action=purge" for that page will have the same effect. Or you can simply wait — cached pages usually get refreshed within 24 hours or less.
If there are certain wiki pages that you want to never be cached, you can install the [[mws:Extension:MagicNoCache|MagicNoCache]] extension, and add the string "<nowiki>__NOCACHE__</nowiki>" to anywhere within those pages.
If there are certain wiki pages that you want to never be cached, you can install the [[mws:Extension:MagicNoCache|MagicNoCache]] extension, and add the string "<nowiki>__NOCACHE__</nowiki>" to anywhere within those pages.
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Wikidata is, in some sense, the fulfillment of the original dream of Semantic MediaWiki. SMW began as a proposal to allow for a "semantic Wikipedia", that could query and export its own data; and much of the early development of SMW was motivated by that goal. However, Wikipedia has a number of special requirements that SMW by itself is unable to fulfill, and that made something like Wikidata necessary: these include, most notably, the fact that the same data is meant to be displayed across a wide variety of languages, and the fact that every piece of information requires a citation.
Wikidata is, in some sense, the fulfillment of the original dream of Semantic MediaWiki. SMW began as a proposal to allow for a "semantic Wikipedia", that could query and export its own data; and much of the early development of SMW was motivated by that goal. However, Wikipedia has a number of special requirements that SMW by itself is unable to fulfill, and that made something like Wikidata necessary: these include, most notably, the fact that the same data is meant to be displayed across a wide variety of languages, and the fact that every piece of information requires a citation.
−
Some of the Wikidata team, most notably Wikidata
project leader
[[Denny Vrandecic|Denny Vrandečić]], began as members of the SMW community.
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Some of the Wikidata team, most notably Wikidata
founder
[[Denny Vrandecic|Denny Vrandečić]], began as members of the SMW community.
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The software that powers Wikidata is a set of MediaWiki extensions collectively known as [[mw:Wikibase|Wikibase]], and though Wikibase has similarities to Semantic MediaWiki, it is a distinct set of software. However,
much
of SMW's backend code
is currently being
spun off into a separate library,
to be
called "DataValues", that both SMW and Wikibase
will use
as a framework for storing data.
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The software that powers Wikidata is a set of MediaWiki extensions collectively known as [[mw:Wikibase|Wikibase]], and though Wikibase has similarities to Semantic MediaWiki, it is a distinct set of software. However,
some
of SMW's backend code
has been
spun off into a separate library, called "DataValues", that
is used by
both SMW and Wikibase as a framework for storing data.
There is the potential that Wikibase and Semantic MediaWiki will compete against one another as software, with some wikis choosing to use Wikibase instead of SMW as their data storage system. This seems doubtful, however: the Wikibase user interface is geared for a highly multilingual, highly general knowledge base like Wikipedia. Wikis with a specific focus and only one or a handful of languages would be better off with the greater structure and simplicity of Semantic MediaWiki.
There is the potential that Wikibase and Semantic MediaWiki will compete against one another as software, with some wikis choosing to use Wikibase instead of SMW as their data storage system. This seems doubtful, however: the Wikibase user interface is geared for a highly multilingual, highly general knowledge base like Wikipedia. Wikis with a specific focus and only one or a handful of languages would be better off with the greater structure and simplicity of Semantic MediaWiki.
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We truly believe that there's no other software yet, either free or proprietary, that enables flexible, collaborative data structures in the way that Semantic MediaWiki does. Nonetheless, within corporations, [http://sharepoint.microsoft.com Microsoft SharePoint] comes up fairly often as an alternative option ([http://wikiworks.com/semantic-mediawiki-vs-sharepoint.html see here] for one view of the advantages of SMW over SharePoint).
We truly believe that there's no other software yet, either free or proprietary, that enables flexible, collaborative data structures in the way that Semantic MediaWiki does. Nonetheless, within corporations, [http://sharepoint.microsoft.com Microsoft SharePoint] comes up fairly often as an alternative option ([http://wikiworks.com/semantic-mediawiki-vs-sharepoint.html see here] for one view of the advantages of SMW over SharePoint).
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There are [http://semanticweb.org/wiki/Semantic_wiki_projects#Active various other semantic wiki applications], although until now
we've only heard
of
[http://www.zagile.com/products/wikidsmart.html Wikidsmart], an extension
to
[http://www.atlassian.com/software/confluence/ Confluence], being considered for use as a direct substitute for
Semantic MediaWiki
, probably due to the popularity of the Confluence wiki engine
.
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There are [http://semanticweb.org/wiki/Semantic_wiki_projects#Active various other semantic wiki applications], although until now
none
of
them have achieved anything close
to
the user base and name recognition of
Semantic MediaWiki.
SMW shares some of the characteristics of [[wp:en:Document-oriented database|document-oriented databases]] like [http://www.mongodb.org/ MongoDB], although SMW functions more like a front-end application than such databases usually do, so they're rarely seen as alternatives.
SMW shares some of the characteristics of [[wp:en:Document-oriented database|document-oriented databases]] like [http://www.mongodb.org/ MongoDB], although SMW functions more like a front-end application than such databases usually do, so they're rarely seen as alternatives.
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In the MediaWiki world, the [[mws:Extension:DynamicPageList_(Wikimedia)|DynamicPageList]] (DPL) extension is sometimes compared to SMW. It, too, allows for querying pages, although it doesn't support semantic annotations: all its queries are based on categories and other standard MediaWiki attributes, like the date a page was last revised.
DPL's one big strength over SMW is its support of querying such page metadata, like the number of revisions to a page, which SMW doesn't support.
There's no rule against using both, though, and [http://smw.referata.com/wiki/Special:BrowseData/Sites?Other_extensions=DPL some wikis do use the two in conjunction].
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In the MediaWiki world, the [[mws:Extension:DynamicPageList_(Wikimedia)|DynamicPageList]] (DPL) extension is sometimes compared to SMW. It, too, allows for querying pages, although it doesn't support semantic annotations: all its queries are based on categories and other standard MediaWiki attributes, like the date a page was last revised. There's no rule against using both, though, and [http://smw.referata.com/wiki/Special:BrowseData/Sites?Other_extensions=DPL some wikis do use the two in conjunction].
In the big picture, the real competitor to Semantic MediaWiki is every so-called "[[wp:en:Turnkey|turnkey]]" application, meant to store a specific type of data. We would like to see the users of many of these applications consider switching to SMW as a cheap, flexible alternative.
In the big picture, the real competitor to Semantic MediaWiki is every so-called "[[wp:en:Turnkey|turnkey]]" application, meant to store a specific type of data. We would like to see the users of many of these applications consider switching to SMW as a cheap, flexible alternative.
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There is a twice-yearly meeting of SMW users and developers, called "[[SMWCon]]", or the Semantic MediaWiki Conference, that has been held alternately in the United States and Europe since 2010. The next SMWCon event will be [[SMWCon Spring 2014]], to be held May 21-23 in Montreal, Canada.
There is a twice-yearly meeting of SMW users and developers, called "[[SMWCon]]", or the Semantic MediaWiki Conference, that has been held alternately in the United States and Europe since 2010. The next SMWCon event will be [[SMWCon Spring 2014]], to be held May 21-23 in Montreal, Canada.
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There are other events where SMW is often discussed. The annual [[meta:Wikimania|Wikimania]] conference has
so far always had
a contingent
of
SMW developers (SMW was in fact first proposed at the first Wikimania, in 2005). The [http://
semtechbizsf2013
.semanticweb.com/ Semantic Technology Conference], or SemTech, almost always has some SMW developers and users, as well as SMW-related talks. The [http://www.wikisym.org/ WikiSym] event series has SMW-related topics from time to time.
+
There are other events where SMW is often discussed. The annual [[meta:Wikimania|Wikimania]] conference
usually
has a contingent SMW developers (SMW was in fact first proposed at the first Wikimania, in 2005). The [http://
semtechbizsj2014
.semanticweb.com/ Semantic Technology Conference], or SemTech, almost always has some SMW developers and users, as well as SMW-related talks. The [http://www.wikisym.org/ WikiSym] event series has SMW-related topics from time to time.
==There's so much documentation! How do I get started?==
==There's so much documentation! How do I get started?==