InstantCommons/pt-br



InstantCommons é um recurso do MediaWiki para permitir o uso de qualquer arquivo de mídia carregado no Wikimedia Commons em qualquer instalação MediaWiki. As wikis com o InstantCommons ativado criam um cache do conteúdo do Commons de modo que o donwload só é feito uma vez e as visualizações de páginas subsequentes carregam a cópia local existente.

Para uma lista de usuários do InstantCommons, ver Sites usando o InstantCommons (em inglês)

Análise
As of July 2015, Wikimedia Commons, the central media repository hosted by the Wikimedia Foundation, contains over 26 million files. Each of these files is available under a free content license or in the public domain; there are no other restrictions of use beyond those relating to use of official insignia or trademarks. Licenses which limit commercial use are considered non-free.

Ao mesmo tempo que o entendimento sobre o Commons aumenta, o desejo de sites de terceiros em usar e contribuir com seu conteúdo também aumentou. Atualmente é tecnicamente possível carregar imagens diretamente dos servidores da Wikimedia no contexto de qualquer página da web. Tal hotlinking é permitido, mas é problemático por várias razões: InstantCommons seeks to address all this by providing an easy method for cached loading of images and metadata from Wikimedia's servers. The first implementation of InstantCommons will be within MediaWiki, allowing for all MediaWiki image operations (thumbnailing, captioning, galleries, etc.) to be performed transparently. However, other wiki engines can implement InstantCommons-like functionality using the API operations described below.
 * Não respeita os termos da licença da imagem e não permite que outros metadados sejam transportados de forma confiável
 * Além de não creditar devidamente o autor do arquivo de mídia, também não dá crédito à Wikimedia
 * Consome largura de banda da Wikimedia a cada visualização de página (a menos que a imagem tenha sido armazenado em cache no lado do cliente ou através de um proxy)
 * Não facilita as operações de imagem úteis, tais como a geração de miniatura e de legenda e é difícil de usar no contexto de uma Wiki, particularmente para operações de formatação de layouts
 * Seé vincula à URLs como identificadores de recursos, o que complica o espelhamento
 * Cria um uso web externo impossível de rastrear, onde qualquer alteração no lado do Wikimedia afeta necessariamente esses usuários externos
 * Não permite a visualização off-line, o que é crucial para os países que têm apenas o acesso à rede intermitente.

Basic feature set
During the installation, the site administrator can choose whether to enable InstantCommons. Ideally, however, the feature should be enabled by default (provided a writable upload directory is specified) to allow the largest possible number of users to use Wikimedia Commons content.

If the feature is enabled, the wiki behaves like a Wikimedia project, that is, if an image or other media file is referred to which exists on Commons, it can be included in a wiki page like a locally uploaded file by specifying its name. Local filenames take precedence over Commons filenames.

Configuração
For enabling InstantCommons in MediaWiki version 1.16 or later, it is sufficient to add the line

to your LocalSettings.php (see for details).

For enabling in MediaWiki versions 1.13-1.15, see here.

HTTPS
Starting June 2015, Wikimedia Commons can only be accessed using HTTPS. Some installs may be missing their root certificate store which prevents MediaWiki from contacting Commons over HTTPS. If InstantCommons stopped working, try:
 * Installing the php curl extension. (It is generally more reliable, and more likely to have proper certificates already installed.) On debian/ubuntu:
 * Verify you have an up-to-date certificate store. If you have the php curl extension installed, follow the instructions here.

SElinux
If your server OS implements SElinux, please take a look at the dedicated section on the SElinux settings page, and make sure HTTPD scripts and modules can access the network successfully. If SElinux prevents HTTPD scripts and modules from connecting to WikiMedia Commons repository, the InstantCommons feature will simply not work.

Behind a firewall
If the server on which the wiki runs is behind a firewall, the wiki server must be granted outgoing http/https requests to commons.wikimedia.org and upload.wikimedia.org, for Instant Commons to work. The IP address ranges are found at IP addresses.

Using files via InstantCommons
With InstantCommons enabled, you can choose any image from Wikimedia Commons (e.g. ), click the "Use this file" button (the button with the wiki icon next to) and paste the markup in your wiki. In our example, pasting

will render the thumbnail (as can be seen on the right side of this page).

Note that when using files in this way you will still need to respect any licensing and other file use legal requirements - see Commons:Reusing content outside Wikimedia.

Scalability considerations
Because the InstantCommons feature allows a wiki user to download resources from the Wikimedia servers, it is crucial that there is no possibility of a Denial of Service attack against either the using wiki, or the Wikimedia Commons, for example, by pasting 30K of links to the largest files on Wikimedia Commons into a wiki page and pressing "preview". Therefore, every successful InstantCommons request will have to be logged by the InstantCommons-enabled wiki together with the originating user or IP address and the time of the request. If an individual user overrides a generous internal bandwidth limitation (could be as high as 1 GB by default, but should be user-configurable), future images will not be downloaded within a 24 hour period. This limitation should not exist for wiki administrators (if a wiki admin wants to conduct a denial of service attack against his own wiki, they do not need to be stopped from doing so; if they want to conduct an attack against Wikimedia, they cannot be stopped from doing so except on Wikimedia's end). In addition to the per-user bandwidth limit, there could be a limit on the size of files which should be downloaded transparently. This would primarily be because files above a certain size would delay pageviews significantly and might even cause the page request to time out. It might be desirable to use an external application for the purpose of downloading these files, so that it can be done in the background without causing the page request to continue. Finally, there could be a total maximum size for the InstantCommons cache; if this size is exceeded, no further files would be downloaded.

While it is unlikely that individual wikis using the InstantCommons feature would cause a significant increase in cost for the Wikimedia Foundation (since every file only has to be downloaded once, and there are per-user bandwidth limitations), it would nevertheless be fair and reasonable for projects using the feature to include a notice on InstantCommons description pages such as: "This file comes from Wikimedia Commons, a media archive hosted by the Wikimedia Foundation. If you would like to support the Wikimedia Foundation, you can donate here ..."

Future potential
In the future, it may be desirable to offer a publisher/subscribe model of changes, which will require wiki-to-wiki authentication and a database of images which are used in subscribing wikis. This would also open up the threat of cross-wiki vandalism, which could be addressed using a delay phase of 24 hours or more for changes to take effect. Two-way functionality is another possibility, that is, to allow uploading free media directly to Commons from any wiki installation. However, this will require federated authentication as a minimum. It may also necessitate cross-wiki communication facilities to notify users from other wikis about Commons policies, which could be part of a larger project like LiquidThreads.

Ver também

 * PhotoCommons: Wordpress plug-in to provide the same functionality