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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title xmlns:d="http://docbook.org/ns/docbook">Chapter 2. Upstream Metadata</title><link rel="stylesheet" type="text/css" href="Common_Content/css/default.css" /><link rel="stylesheet" media="print" href="Common_Content/css/print.css" type="text/css" /><meta xmlns:d="http://docbook.org/ns/docbook" name="generator" content="publican v4.3.2" /><meta xmlns:d="http://docbook.org/ns/docbook" name="package" content="AppStream-AppStream-0.11-en-US-0.0-0" /><link rel="home" href="index.html" title="AppStream" /><link rel="up" href="index.html" title="AppStream" /><link rel="prev" href="chap-AppStream-About.html" title="Chapter 1. About AppStream" /><link rel="next" href="sect-Metadata-Application.html" title="2.2. Desktop Applications" /></head><body><p id="title"><a class="left" href="http://www.freedesktop.org/wiki/Distributions/AppStream/"><img alt="Product Site" src="Common_Content/images//image_left.png" /></a><a class="right" href="http://www.freedesktop.org/software/appstream/docs/"><img alt="Documentation Site" src="Common_Content/images//image_right.png" /></a></p><ul class="docnav top"><li class="previous"><a accesskey="p" href="chap-AppStream-About.html"><strong>Prev</strong></a></li><li class="home">AppStream</li><li class="next"><a accesskey="n" href="sect-Metadata-Application.html"><strong>Next</strong></a></li></ul><div xml:lang="en-US" class="chapter" lang="en-US"><div class="titlepage"><div><div><h1 class="title"><a id="chap-Metadata">
</a>Chapter 2. Upstream Metadata</h1></div></div></div><div class="toc"><dl class="toc"><dt><span class="section"><a href="chap-Metadata.html#sect-Metadata-GenericComponent">2.1. Generic Component</a></span></dt><dt><span class="section"><a href="sect-Metadata-Application.html">2.2. Desktop Applications</a></span></dt><dt><span class="section"><a href="sect-Metadata-ConsoleApplication.html">2.3. Console Applications</a></span></dt><dt><span class="section"><a href="sect-Metadata-WebApplication.html">2.4. Web Applications</a></span></dt><dt><span class="section"><a href="sect-Metadata-Service.html">2.5. Services</a></span></dt><dt><span class="section"><a href="sect-Metadata-Addon.html">2.6. Addons</a></span></dt><dt><span class="section"><a href="sect-Metadata-Fonts.html">2.7. Fonts</a></span></dt><dt><span class="section"><a href="sect-Metadata-Codec.html">2.8. Codecs</a></span></dt><dt><span class="section"><a href="sect-Metadata-InputMethod.html">2.9. Input Methods</a></span></dt><dt><span class="section"><a href="sect-Metadata-Firmware.html">2.10. Firmware</a></span></dt><dt><span class="section"><a href="sect-Metadata-Driver.html">2.11. Driver</a></span></dt><dt><span class="section"><a href="sect-Metadata-Localization.html">2.12. Localization</a></span></dt></dl></div><div class="para">
AppStream allows upstream projects to define metadata about the components they provide using small XML files, metainfo files, which get installed into locations on the client system and are used by distribuors to enhance their metadata.
</div><div class="para">
A "component" is a piece of software, like an application, a library, a font or a codec. For several components, especially those which are shown in software-centers, we provide specialized metainfo files to define specific properties and data of these components. For example, applications and fonts support screenshots, while codecs don't.
</div><div class="para">
All metainfo files need to contain a minimal amount of information, defined in the "Generic Component" section, which also describes some optional elements which can be used. Specialized components might require more information to be complete and valid.
</div><div class="para">
The XML in metainfo files does not need any XML namespace, and adding one should generally be avoided. If you want to use a namespace though (maybe in case you want to embed the data in other contexts), the xmlns should be <code class="code">https://specifications.freedesktop.org/metainfo/1.0</code>.
</div><div xml:lang="en-US" class="section" lang="en-US"><div class="titlepage"><div><div><h2 class="title"><a id="sect-Metadata-GenericComponent">
</a>2.1. Generic Component</h2></div></div></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="spec-component-introduction">
</a>2.1.1. Introduction</h3></div></div></div><div class="para">
For a distribution, it is good to know more about the content of a package. Which public interfaces (libraries? Python modules?) does it provide? Does it contain codecs? Does it contain firmware? Fonts? An application? All of this information can be used to automatically install missing software or to offer users a choice on what they want to install from a software center.
</div><div class="para">
To provide this information, we created the <span class="italic italic">metainfo</span> files, which allow <span class="bold bold"><strong>upstream projects</strong></span> to describe the content of their software package. If a metainfo file contains a <code class="literal"><provides/></code> tag, distributors must also ensure that the package providing the file contains all items referenced by that statement, or is installed by a metapackage depending on packages which provide these items. This gives upstream projects a (very light) way to influence distributor packaging. More information about that can be found below.
</div><div class="para">
Several specialized component-metainfo files exist, for example for applications or fonts. These are all based on this generic component XML specification, and are described in the following chapters.
</div></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="spec-component-location">
</a>2.1.2. Filesystem locations</h3></div></div></div><div class="para">
Upstream projects can ship one or more metainfo files in <code class="filename">/usr/share/metainfo/%{id}.metainfo.xml</code>, where <code class="literal">id</code> is a unique identifier of this specific component.
</div><div xmlns:d="http://docbook.org/ns/docbook" class="note"><div class="admonition_header"><p><strong>Note</strong></p></div><div class="admonition"><div class="para">
Applications are a special case here, because they are usually treated differently by software centers (and also for historical reasons). If your metainfo file contains an application, as described in <a class="xref" href="sect-Metadata-Application.html">Section 2.2, “Desktop Applications”</a>, you may want to install it as <code class="filename">/usr/share/metainfo/%{id}.appdata.xml</code>.
</div></div></div><div xmlns:d="http://docbook.org/ns/docbook" class="important"><div class="admonition_header"><p><strong>Legacy Path</strong></p></div><div class="admonition"><div class="para">
The <code class="filename">/usr/share/appdata/</code> path must be scanned by AppStream tools as well, to support legacy applications installing metadata there. For new software components, it is advised not to use this directory.
</div></div></div></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="spec-component-filespec">
</a>2.1.3. XML Specification</h3></div></div></div><div class="para">
The XML for a generic component definition starts with a <code class="code"><component></code> tag as the root element. The <code class="code"><component></code> element must at least have an <code class="literal">id</code>, <code class="literal">name</code> and <code class="literal">summary</code> tag; and a <code class="literal">provides</code> tag with appropriate children is highly recommended. All possible tags in the generic set are:
</div><div class="variablelist"><dl class="variablelist"><dt><a id="tag-id-generic">
</a><span class="term"><id/></span></dt><dd><div class="para">
The <code class="code"><id></code> tag is a unique identifier for this component. It must contain only ASCII characters, dots, hyphens and numbers. Spaces are not allowed. While hyphens are allowed for legacy compatibility, their usage is strongly discouraged to ensure interoperability of the AppStream ID with other tools such as D-Bus (and thereby making the ID more generic and useful). It is also strongly discouraged to start any segment of the ID with a digit.
</div><div class="para">
The ID must follow a reverse-DNS scheme, consisting of <code class="literal">{tld}.{vendor}.{product}</code>, for example <code class="code">org.kde.Gwenview</code> or <code class="code">com.hugski.ColorHug2</code>. Ownership of <code class="literal">{vendor}.{tld}</code> in the domain name system guarantees uniqueness of IDs.
</div><div class="para">
To increase the uniqueness and to distinguish between different pieces of a software suite, it is suggested to append the type name to the component-id in these cases. For example, one can use <code class="code">com.hugski.ColorHug2</code> for the client tools to control hardware, and <code class="code">com.hugski.ColorHug2.firmware</code> for the runtime firmware files.
</div><div class="para">
Note that the value of this tag must be <span class="emphasis"><em>unique</em></span> across all distributions and software deployment platforms. In case it is not unique, distributors are expected to reject the conflicting components from inclusion into their metadata and notify the upstream projects about this issue.
</div><div xmlns:d="http://docbook.org/ns/docbook" class="important"><div class="admonition_header"><p><strong>Escaping characters in the component ID</strong></p></div><div class="admonition"><div class="para">
To ensures the greatest possible compatibility of an AppStream ID, it is recommended to replace any hyphens in the ID with underscores, and prefix every leading digit of a section with an underscore as well. Since the underscore is not a valid character in domain names, the uniqueness of the ID is kept. For example, the ID <code class="code">org.7-zip.7Zip</code> could become <code class="code">org._7_zip._7Zip</code>.
</div></div></div></dd><dt><a id="tag-metadata_license">
</a><span class="term"><metadata_license/></span></dt><dd><div class="para">
The <code class="code"><metadata_license/></code> tag indicates the content license that you are releasing the one metainfo XML file under. This is typically not the same as the project license. Omitting the license value can result in your data not being incorporated into the distribution metadata (so this is a required tag).
</div><div class="para">
A <a href="https://en.wikipedia.org/wiki/Permissive_software_licence">permissive</a> license ensures your data can be combined with arbitrary other data in one file (this means copyleft licenses like the GPL are not suitable as metadata license). Valid permissive licenses include:
</div><div xmlns:d="http://docbook.org/ns/docbook" class="itemizedlist"><ul><li class="listitem"><div class="para">
<code class="literal">CC0-1.0</code>
</div></li><li class="listitem"><div class="para">
<code class="literal">CC-BY-3.0</code>
</div></li><li class="listitem"><div class="para">
<code class="literal">CC-BY-SA-3.0</code>
</div></li><li class="listitem"><div class="para">
<code class="literal">GFDL-1.3</code>
</div></li><li class="listitem"><div class="para">
<code class="literal">MIT</code>
</div></li><li class="listitem"><div class="para">
<code class="literal">FSFAP</code>
</div></li></ul></div><div class="para">
The license codes correspond to the identifiers found at the <a href="http://spdx.org/licenses/">SPDX OpenSource License Registry</a>. For instance, <code class="literal">CC-BY-SA-3.0</code> corresponds to the license at <a href="http://creativecommons.org/licenses/by-sa/3.0/">creativecommons.org/licenses/by-sa/3.0</a>.
</div></dd><dt><a id="tag-name">
</a><span class="term"><name/></span></dt><dd><div class="para">
A human-readable name for this software component. For example, if the component ID was "libc", its name might be "GNU Standard C Library".
</div></dd><dt><a id="tag-summary">
</a><span class="term"><summary/></span></dt><dd><div class="para">
A short summary of what this component does. If the component is "PackageKit", the summary could be "Provides a package-management abstraction layer".
</div></dd><dt><a id="tag-icon">
</a><span class="term"><icon/></span></dt><dd><div class="para">
The <code class="code"><icon/></code> tag describes the component icon. It is mostly used for GUI applications (component-type <code class="literal">desktop-application</code>). It can be of type <code class="literal">stock</code>, <code class="literal">local</code> or <code class="literal">remote</code>.
</div><div class="para">
<code class="literal">stock</code> icons are loaded from the icon stock (the current or hicolor/locolor fallback themes). The icon name must not include any file-extension or path.
</div><div class="para">
<code class="literal">local</code> icons are loaded from a file in the filesystem. They should specify a full file path. This icon type may have <code class="literal">width</code> and <code class="literal">height</code> properties.
</div><div class="para">
<code class="literal">remote</code> icons loaded from a remote URL. Currently, only HTTP/HTTPS urls are supported. This icon type should have <code class="literal">width</code> and <code class="literal">height</code> properties.
</div></dd><dt><a id="tag-description">
</a><span class="term"><description/></span></dt><dd><div class="para">
A long description of this component. Some markup can be used.
</div><div class="para">
Do not assume the format is HTML. Only paragraph (<code class="literal">p</code>), ordered list (<code class="literal">ol</code>) and unordered list (<code class="literal">ul</code>) are supported at this time.
</div><div class="para">
In metainfo files, this tag should be translated by-paragraph, meaning that in a translated file, each translated <code class="literal"><p/></code> child has a language property.
</div></dd><dt><a id="tag-categories">
</a><span class="term"><categories/></span></dt><dd><div class="para">
This tag can contain one or more <code class="code"><category>></code> entries, describing the categories this software component is associated with. This tag is usually applied to components of type <code class="literal">desktop-application</code>, but can be used with any component. A list of valid category names can be found in the <a href="http://standards.freedesktop.org/menu-spec/latest/apa.html">Freedesktop menu spec</a>. Example:
</div><pre class="programlisting"><span xmlns="" class="line"></span><span xmlns="" class="perl_Keyword"><categories></span>
<span xmlns="" class="line"></span> <span xmlns="" class="perl_Keyword"><category></span>Game<span xmlns="" class="perl_Keyword"></category></span>
<span xmlns="" class="line"></span> <span xmlns="" class="perl_Keyword"><category></span>ArcadeGame<span xmlns="" class="perl_Keyword"></category></span>
<span xmlns="" class="line"></span><span xmlns="" class="perl_Keyword"></categories></span></pre></dd><dt><a id="tag-url">
</a><span class="term"><url/></span></dt><dd><div class="para">
Defines web URLs for this component.There are several different URL types allowed:
</div><div class="variablelist"><dl class="variablelist"><dt><span class="term">homepage</span></dt><dd><div class="para">
Should be a link to the upstream homepage for the component.
</div></dd><dt><span class="term">bugtracker</span></dt><dd><div class="para">
Should point to the software's bug tracking system, for users to report new bugs.
</div></dd><dt><span class="term">faq</span></dt><dd><div class="para">
Should link a FAQ page for this software, to answer some of the most-asked questions in detail, something which you cannot do in the component's description.
</div></dd><dt><span class="term">help</span></dt><dd><div class="para">
Should provide a web link to an online user's reference, a software manual or help page.
</div></dd><dt><span class="term">donation</span></dt><dd><div class="para">
URLs of this type should point to a webpage showing information on how to donate to the described software project.
</div></dd><dt><span class="term">translate</span></dt><dd><div class="para">
URLs of this type should point to a webpage where users can submit or modify translations of the upstream project.
</div><div class="para">
Typically this should be a link to the project page in Weblate, Transifex or Zanata, but could also be a link to an upstream-hosted wiki page describing how to send translations upstream.
</div></dd></dl></div></dd><dt><a id="tag-launchable">
</a><span class="term"><launchable/></span></dt><dd><div class="para">
This optional tag indicates possible methods to launch the software described in this component. It is allowed to appear multiple times in the metainfo data.
</div><div class="para">
The <code class="code"><launchable/></code> tag has a essential <code class="literal">type</code> property indicating the system that is used to launch the component. The following types are allowed:
</div><div class="variablelist"><dl class="variablelist"><dt><span class="term">desktop-id</span></dt><dd><div class="para">
The application can be launched via a desktop file. The value of the tag is a <a href="https://standards.freedesktop.org/desktop-entry-spec/desktop-entry-spec-latest.html#desktop-file-id">desktop-file id</a>.
</div><div class="para">
In case a software component has multiple launchable entries, the software center might display a dialog to choose which entry to launch. If possible though, it should be avoided to add multiple <code class="literal">launchable</code> tags of type <code class="literal">desktop-id</code>.
</div></dd><dt><span class="term">service</span></dt><dd><div class="para">
The software can be started, stopped, and monitored by the OS "init" facility, such as systemd. The value of the tag is a name that can be used with that facility, such as a systemd unit name.
</div><div class="para">
Multiple <code class="literal">launchable</code> tags of type <code class="literal">service</code> are not alternatives to start the same service, but the component does contain multiple services that might all need to be started.
</div><div class="para">
Only those services should be listed as launchables that the user is actually expected to start and stop manually. Services that are started/stopped indirectly via dependencies of other services should not be listed.
</div><div class="para">
For systemd units, the services listed as launchables are expected to support enabling and disabling.
</div></dd><dt><span class="term">cockpit-manifest</span></dt><dd><div class="para">
The software can be launched from the menus of the <a href="http://cockpit-project.org">Cockpit</a> admin interface. The value of the tag is the name of a <a href="http://cockpit-project.org/guide/latest/packages.html">Cockpit package</a>.
</div></dd><dt><span class="term">url</span></dt><dd><div class="para">
The application is a web site that is viewed through a browser. The value of the tag is a direct HTTP/HTTPS URL that the browser must navigate to.
</div></dd></dl></div><div class="para">
Example:
</div><pre class="programlisting"><span xmlns="" class="line"></span><span xmlns="" class="perl_Keyword"><launchable</span><span xmlns="" class="perl_Others"> type=</span><span xmlns="" class="perl_String">"desktop-id"</span><span xmlns="" class="perl_Keyword">></span>org.gnome.Sysprof2.desktop<span xmlns="" class="perl_Keyword"></launchable></span></pre></dd><dt><a id="tag-releases">
</a><span class="term"><releases/></span></dt><dd><div class="para">
The <code class="code"><releases></code> tag contains <code class="code"><release/></code> child tags which describe some metainformation about the current release of the described software. The <code class="code"><release/></code> tag may be present multiple times (for older releases), but a tag for the current version must always be present.
</div><div class="para">
A <code class="literal">release</code> tag can have the properties <code class="literal">version</code>, <code class="literal">date</code> and <code class="literal">timestamp</code>. The <code class="literal">date</code> property can have any time in <a href="https://en.wikipedia.org/wiki/ISO_8601">ISO 8601</a> format as its value and should be present for every release. The <code class="literal">timestamp</code> tag contains the release time in the form of a UNIX epoch. This tag should not be used in metainfo files in newly written metadata, but will still be parsed in case it is present. The the <code class="literal">timestamp</code> property is mainly used in generated distro-metadata. In case both release-time tags are present, the <code class="literal">timestamp</code> tag will take precedence over <code class="literal">date</code>.
</div><div class="para">
Optionally, the <code class="code"><release/></code> tag may also have an <code class="literal">urgency</code> property, having one of the following values:
</div><div xmlns:d="http://docbook.org/ns/docbook" class="itemizedlist"><ul><li class="listitem"><div class="para">
<code class="literal">low</code>
</div></li><li class="listitem"><div class="para">
<code class="literal">medium</code>
</div></li><li class="listitem"><div class="para">
<code class="literal">high</code>
</div></li><li class="listitem"><div class="para">
<code class="literal">critical</code>
</div></li></ul></div><div class="para">
The <code class="literal">urgency</code> defines how important it is to install the new release as an update. This is especially important for <code class="literal">type=firmware</code> components. If no urgency is defined, a <code class="code">medium</code> urgency is implicitly assumed. The urgency defines how the update will be presented to the user, and sometimes if it will be installed automatically and immediately, or delayed.
</div><div class="para">
Each <code class="literal">release</code> tag may have a <code class="literal">description</code> tag as child, containing a brief description of what is new in the release. The <code class="literal">description</code> tag is structured as described in <a class="xref" href="chap-Metadata.html#tag-description"><description/></a>.
</div><div class="para">
A <code class="literal">release</code> tag may also have one or multiple <code class="literal">size</code> tags as children, which define the installed and download size of this component release. This is useful in case the component does not have a corresponding native package in a distribution, for example if it is a Limba bundle or LVFS firmware. The size type is defined via a <code class="literal">type</code> property on the <code class="literal">size</code> tag, and may assume the value <code class="code">download</code> or <code class="code">installed</code>. The size itself is set as the value and must be given in bytes.
</div><div class="para">
Examples for a valid releases tag:
</div><pre class="programlisting"><span xmlns="" class="line"></span><span xmlns="" class="perl_Keyword"><releases></span>
<span xmlns="" class="line"></span> <span xmlns="" class="perl_Keyword"><release</span><span xmlns="" class="perl_Others"> version=</span><span xmlns="" class="perl_String">"1.2"</span><span xmlns="" class="perl_Others"> date=</span><span xmlns="" class="perl_String">"2014-04-12"</span><span xmlns="" class="perl_Others"> urgency=</span><span xmlns="" class="perl_String">"high"</span><span xmlns="" class="perl_Keyword">></span>
<span xmlns="" class="line"></span> <span xmlns="" class="perl_Keyword"><size</span><span xmlns="" class="perl_Others"> type=</span><span xmlns="" class="perl_String">"download"</span><span xmlns="" class="perl_Keyword">></span>12345678<span xmlns="" class="perl_Keyword"></size></span>
<span xmlns="" class="line"></span> <span xmlns="" class="perl_Keyword"><size</span><span xmlns="" class="perl_Others"> type=</span><span xmlns="" class="perl_String">"installed"</span><span xmlns="" class="perl_Keyword">></span>42424242<span xmlns="" class="perl_Keyword"></size></span>
<span xmlns="" class="line"></span> <span xmlns="" class="perl_Keyword"></release></span>
<span xmlns="" class="line"></span> <span xmlns="" class="perl_Keyword"><release</span><span xmlns="" class="perl_Others"> version=</span><span xmlns="" class="perl_String">"1.0"</span><span xmlns="" class="perl_Others"> date=</span><span xmlns="" class="perl_String">"2012-08-26"</span> <span xmlns="" class="perl_Keyword">/></span>
<span xmlns="" class="line"></span><span xmlns="" class="perl_Keyword"></releases></span></pre></dd><dt><a id="tag-provides">
</a><span class="term"><provides/></span></dt><dd><div class="para">
The <code class="literal">provides</code> tag and its children describe the public interfaces this application provides. A public interface can be anything which other applications, which are not part of the upstream project, can access or reference. This includes binaries and libraries. Private interfaces should never be added to a <code class="literal">provides</code> tag.
</div><div class="para">
A <code class="literal">provides</code> tag contain a number of children describing the type and name of the provided public interface items. It is suggested that the build system auto-generates this tag and its children. Currently allowed item types are listed below. If you miss something, <a href="https://github.com/ximion/appstream/issues/new">file a bug against AppStream</a> so we can add the new type.
</div><div class="variablelist"><dl class="variablelist"><dt><span class="term"><library/></span></dt><dd><div class="para">
Contains the name of a shared library placed in a publicly accessible library path, such as <code class="filename">/usr/lib</code>, <code class="filename">/usr/lib/<triplet></code> or <code class="filename">/lib</code>. For example, for the libappstream library, the value for <code class="literal">library</code> would be <strong class="userinput"><code>libappstream.so.1</code></strong>.
</div></dd><dt><span class="term"><binary/></span></dt><dd><div class="para">
Name of a binary installed into a location in <code class="envar">PATH</code>.
</div></dd><dt><span class="term"><font/></span></dt><dd><div class="para">
Full name of a font provided by this component. See <a class="xref" href="sect-Metadata-Fonts.html">Section 2.7, “Fonts”</a> for more information.
</div></dd><dt><span class="term"><modalias/></span></dt><dd><div class="para">
A modalias glob representing the hardware types (for example USB, PCI, ACPI, DMI) this component handles. Useful for installing printer drivers or other USB protocol drivers for smartphones, firmware, and out of tree kernel drivers.
</div></dd><dt><span class="term"><firmware/></span></dt><dd><div class="para">
This provided element is described in details for the <code class="literal">firmware</code> component type, where it is mandatory. Please see <a class="xref" href="sect-Metadata-Firmware.html#tag-firmware-provides"><provides/> ↪ <firmware/></a> for more information.
</div></dd><dt><span class="term"><python2/></span></dt><dd><div class="para">
Name of a Python 2 module this component provides.
</div></dd><dt><span class="term"><python3/></span></dt><dd><div class="para">
Name of a Python 3 module this component provides.
</div></dd><dt><span class="term"><dbus/></span></dt><dd><div class="para">
Contains the well-known name of a D-Bus service as its value. The type of the service must be specified using the <code class="literal">type</code> property of this tag. Allowed values are <code class="code">user</code> and <code class="code">system</code>.
</div><div class="para">
Example:
</div><pre class="programlisting"><span xmlns="" class="line"></span><span xmlns="" class="perl_Keyword"><provides></span>
<span xmlns="" class="line"></span> <span xmlns="" class="perl_Keyword"><dbus</span><span xmlns="" class="perl_Others"> type=</span><span xmlns="" class="perl_String">"system"</span><span xmlns="" class="perl_Keyword">></span>org.freedesktop.PackageKit<span xmlns="" class="perl_Keyword"></dbus></span>
<span xmlns="" class="line"></span><span xmlns="" class="perl_Keyword"></provides></span></pre></dd><dt><span class="term"><id/></span></dt><dd><div class="para">
Contains the component-ID of another software component. The presence of this tag indicates that the software component containing it is able to provide all functionality of the one referenced in the <code class="code"><provides/> ↪ <id/></code> tag.
</div><div class="para">
This is useful in case a component-id had to be renamed in the past, e.g. because its domain-name changed.
</div></dd></dl></div></dd><dt><a id="tag-mimetypes">
</a><span class="term"><mimetypes/></span></dt><dd><div class="para">
This tag can contain one or more <code class="code"><mimetype/></code> children, describing the MIME types this application supports. This tag is especially useful for generic components and addon-type components. For applications, the metadata will automatically be fetched from their <code class="filename">.desktop</code> files by the distribution's metadata generator. Example:
</div><pre class="programlisting"><span xmlns="" class="line"></span>
<span xmlns="" class="line"></span><span xmlns="" class="perl_Keyword"><mimetypes></span>
<span xmlns="" class="line"></span> <span xmlns="" class="perl_Keyword"><mimetype></span>text/html<span xmlns="" class="perl_Keyword"></mimetype></span>
<span xmlns="" class="line"></span> <span xmlns="" class="perl_Keyword"><mimetype></span>image/jpeg<span xmlns="" class="perl_Keyword"></mimetype></span>
<span xmlns="" class="line"></span> <span xmlns="" class="perl_Keyword"><mimetype></span>application/rss+xml<span xmlns="" class="perl_Keyword"></mimetype></span>
<span xmlns="" class="line"></span> <span xmlns="" class="perl_Keyword"></mimetypes></span></pre></dd><dt><a id="tag-project_group">
</a><span class="term"><project_group/></span></dt><dd><div class="para">
If you include the <code class="code"><project_group/></code> tag then this identifies your project with a specific upstream umbrella project. Known values include <code class="literal">GNOME</code>, <code class="literal">KDE</code>, <code class="literal">XFCE</code>, <code class="literal">MATE</code> and <code class="literal">LXDE</code>, although other umbrella projects like Yorba or Mozilla make sense too.
</div><div xmlns:d="http://docbook.org/ns/docbook" class="note"><div class="admonition_header"><p><strong>Note</strong></p></div><div class="admonition"><div class="para">
You should only identify with an umbrella project if you use <span class="emphasis"><em>all</em></span> their infrastructure and policies, for instance string freezes dates, bugtracker and source control instance.
</div></div></div></dd><dt><a id="tag-project_license">
</a><span class="term"><project_license/></span></dt><dd><div class="para">
The <code class="code"><project_license/></code> tag is indicating the license of the component (application/library/addon/font/etc.) described in the metadata document. It should be a <a href="https://spdx.org/specifications">SPDX license expression</a>. Possible values include:
<div xmlns:d="http://docbook.org/ns/docbook" class="itemizedlist"><ul><li class="listitem"><div class="para">
<code class="literal">GPL-2.0</code>
</div></li><li class="listitem"><div class="para">
<code class="literal">LGPL-3.0+ AND GPL-3.0+</code>
</div></li><li class="listitem"><div class="para">
<code class="literal">MIT</code>
</div></li><li class="listitem"><div class="para">
<code class="literal">CC-BY-SA-2.0</code>
</div></li></ul></div>
A full list of recognized licenses and their identifiers can be found at the <a href="http://spdx.org/licenses/">SPDX OpenSource License Registry</a>.
</div><div class="para">
Although the <code class="literal">project_license</code> tag is not mandatory, it is recommended to include it.
</div></dd><dt><a id="tag-developer_name">
</a><span class="term"><developer_name/></span></dt><dd><div class="para">
The <code class="code"><developer_name/></code> tag is designed to represent the developers or project responsible for development of the project described in the metadata.
</div><div class="para">
Values might be for example "The GNOME Foundation" or "The KDE Community". You must not include hyperlinks or emails in this field, if you want to link to the developer's homepage, use the <a class="xref" href="chap-Metadata.html#tag-url"><url/></a>-tag instead.
</div><div class="para">
This tag is translatable.
</div></dd><dt><a id="tag-screenshots">
</a><span class="term"><screenshots/></span></dt><dd><div class="para">
Visual components (like fonts or graphical applications) may choose to add one or multiple screenshots to their metadata.
</div><div class="para">
The <code class="code"><screenshots/></code> tag contains multiple <code class="code"><screenshot/></code> children, where at least one of them must have the property <code class="code">type="default"</code> to indicate the primary screenshot of the software. Every <code class="code"><screenshot/></code> tag must have at least one <code class="code"><image/></code> child.
</div><div class="para">
The value of the <code class="code"><image/></code> tag is a direct HTTP/HTTPS/FTP URL to a screenshot uploaded to a public location on the web. The <code class="code"><image/></code> tag may have the following properties:
<div xmlns:d="http://docbook.org/ns/docbook" class="itemizedlist"><ul><li class="listitem"><div class="para">
<code class="code">type</code>
</div><div class="para">
The type of the image: <code class="code">source</code> for the source image, and <code class="code">thumbnail</code> for a thumbnail image. In case the type is <code class="code">thumbnail</code>, the <code class="code">width</code> and <code class="code">height</code> properties must be present.
</div></li><li class="listitem"><div class="para">
<code class="code">width</code>
</div><div class="para">
The width of the image in pixels.
</div></li><li class="listitem"><div class="para">
<code class="code">height</code>
</div><div class="para">
The height of the image in pixels.
</div></li><li class="listitem"><div class="para">
<code class="code">xml:lang</code>
</div><div class="para">
The language this screenshot image is translated in. This property should only be present if there are multiple images with different locales present.
</div></li></ul></div>
</div><div class="para">
Optionally, a <code class="code"><screenshot/></code> tag may have a translatable <code class="code"><caption/></code> child, defining a short (ideally not more than 256 characters) description of what the user can see on the referenced screenshot.
</div><div class="para">
Ideally, all screenshots should have a 16:9 aspect ratio, and should have a width that is no smaller than 620 pixels. They should also be in be in PNG or JPEG format. PNG is the preferred format; JPEG should only be used when screenshots include large photographs or other images where a lossy format like JPEG may compress better.
</div><div class="para">
Example:
</div><pre class="programlisting"><span xmlns="" class="line"></span><span xmlns="" class="perl_Keyword"><screenshots></span>
<span xmlns="" class="line"></span> <span xmlns="" class="perl_Keyword"><screenshot</span><span xmlns="" class="perl_Others"> type=</span><span xmlns="" class="perl_String">"default"</span><span xmlns="" class="perl_Keyword">></span>
<span xmlns="" class="line"></span> <span xmlns="" class="perl_Keyword"><caption></span>The FooBar main window.<span xmlns="" class="perl_Keyword"></caption></span>
<span xmlns="" class="line"></span> <span xmlns="" class="perl_Keyword"><image</span><span xmlns="" class="perl_Others"> type=</span><span xmlns="" class="perl_String">"source"</span><span xmlns="" class="perl_Others"> width=</span><span xmlns="" class="perl_String">"1600"</span><span xmlns="" class="perl_Others"> height=</span><span xmlns="" class="perl_String">"900"</span><span xmlns="" class="perl_Keyword">></span>https://example.com/foobar/screenshot-1.png<span xmlns="" class="perl_Keyword"></image></span>
<span xmlns="" class="line"></span> <span xmlns="" class="perl_Keyword"></screenshot></span>
<span xmlns="" class="line"></span> <span xmlns="" class="perl_Keyword"><screenshot></span>
<span xmlns="" class="line"></span> <span xmlns="" class="perl_Keyword"><caption></span>Foobar showing the frobnicate functionality.<span xmlns="" class="perl_Keyword"></caption></span>
<span xmlns="" class="line"></span> <span xmlns="" class="perl_Keyword"><image</span><span xmlns="" class="perl_Others"> type=</span><span xmlns="" class="perl_String">"source"</span><span xmlns="" class="perl_Others"> width=</span><span xmlns="" class="perl_String">"1600"</span><span xmlns="" class="perl_Others"> height=</span><span xmlns="" class="perl_String">"900"</span><span xmlns="" class="perl_Keyword">></span>https://example.com/foobar/screenshot-2.png<span xmlns="" class="perl_Keyword"></image></span>
<span xmlns="" class="line"></span> <span xmlns="" class="perl_Keyword"></screenshot></span>
<span xmlns="" class="line"></span> <span xmlns="" class="perl_Keyword"></screenshots></span></pre></dd><dt><a id="tag-update_contact">
</a><span class="term"><update_contact/></span></dt><dd><div class="para">
The <code class="code"><update_contact/></code> tag is an optional tag which can be added to provide an email address distributors can use to contact the project about invalid or incomplete metadata or – in case the specification has changed – about old metadata. It can also be used to ask general questions in case of an update of the component described in the metadata file.
</div><div class="para">
The <code class="code"><update_contact/></code> tag must <span class="emphasis"><em>only be used by distributors</em></span>. It is not included in the distribution-provided AppStream XML file, and therefore not exposed to the end user via any kind of UI.
</div><div class="para">
Upstream authors might decide to add an email address in cleartext, but spam protection using <code class="code">_AT_</code> is also valid. The value of this tag is generally treated a case-insensitive way.
</div><div class="para">
Example:
</div><pre class="programlisting"><span xmlns="" class="line"></span><span xmlns="" class="perl_Keyword"><update_contact></span>developer_AT_example.com<span xmlns="" class="perl_Keyword"></update_contact></span></pre></dd><dt><a id="tag-translation">
</a><span class="term"><translation/></span></dt><dd><div class="para">
The <code class="code"><translation/></code> tag is an optional tag which can be added to specify the translation domain used for this software component. It may be used by the AppStream distro metadata generator to determine the translation status of the respective software.
</div><div class="para">
The tag must have a <code class="literal">type</code> property, assuming the value of the translation system which is used. Right now, allowed translation systems and values for <code class="literal">type</code> are:
<div xmlns:d="http://docbook.org/ns/docbook" class="itemizedlist"><ul><li class="listitem"><div class="para">
<code class="literal">gettext</code>
</div></li><li class="listitem"><div class="para">
<code class="literal">qt</code>
</div></li></ul></div>
In case a software components gets its translation from multiple translation domains, the <code class="code"><translation/></code> tag may be defined more than once.
</div><div class="para">
Example:
</div><pre class="programlisting"><span xmlns="" class="line"></span><span xmlns="" class="perl_Keyword"><translation</span><span xmlns="" class="perl_Others"> type=</span><span xmlns="" class="perl_String">"gettext"</span><span xmlns="" class="perl_Keyword">></span>foobar<span xmlns="" class="perl_Keyword"></translation></span></pre></dd><dt><a id="tag-suggests">
</a><span class="term"><suggests/></span></dt><dd><div class="para">
The <code class="code"><suggests/></code> tag is an optional tag which can be added to specify the component-ids of other software this components suggests. Software centers might present the suggested software on the installation page of the described component.
</div><div class="para">
The tag may have a <code class="literal">type</code> property, with the value <code class="code">upstream</code>, indicating that this suggestion originates from the upstream project. If no <code class="literal">type</code> property is given, <code class="code">upstream</code> is implicitly assumed as value. Metainfo files must not define other <code class="literal">suggests</code> types, those are reserved for AppStream catalog XML (see <a class="xref" href="chap-CollectionData.html#tag-ct-suggests"><suggests/></a> in catalog XML).
</div><div class="para">
The <code class="literal">suggests</code> tag must have one or more <code class="code"><id/></code> tags as children, specifying the IDs of the suggested other software components.
</div><div class="para">
Example:
</div><pre class="programlisting"><span xmlns="" class="line"></span><span xmlns="" class="perl_Keyword"><suggests></span>
<span xmlns="" class="line"></span> <span xmlns="" class="perl_Keyword"><id></span>org.kde.gwenview.desktop<span xmlns="" class="perl_Keyword"></id></span>
<span xmlns="" class="line"></span> <span xmlns="" class="perl_Keyword"><id></span>org.inkscape.Inkscape<span xmlns="" class="perl_Keyword"></id></span>
<span xmlns="" class="line"></span><span xmlns="" class="perl_Keyword"></suggests></span></pre></dd><dt><a id="tag-content_rating">
</a><span class="term"><content_rating/></span></dt><dd><div class="para">
The <code class="code"><content_rating/></code> tag is an optional tag which can be added to specify age ratings for the respective software components. These maybe be used for parental control or to display their information in software centers.
</div><div class="para">
The tag must have a <code class="literal">type</code> property, indicating the type of the rating system that is used. At the moment, the <a href="https://odrs.gnome.org/oars">Open Age Ratings Service</a> (value <code class="code">oars-1.0</code>) is supported natively, but more services might be added in future.
</div><div class="para">
The <code class="code"><content_rating/></code> must have <code class="code"><content_attribute/></code> children which each have an <code class="literal">id</code> property indicating the specific section that is rated. Their value indicates the intensity of the rated section and can be one of:
</div><div xmlns:d="http://docbook.org/ns/docbook" class="itemizedlist"><ul><li class="listitem"><div class="para">
<code class="literal">none</code> - no rating given
</div></li><li class="listitem"><div class="para">
<code class="literal">mild</code>
</div></li><li class="listitem"><div class="para">
<code class="literal">moderate</code>
</div></li><li class="listitem"><div class="para">
<code class="literal">intense</code>
</div></li></ul></div><div class="para">
The website of the Open Age Ratings Service provides <a href="https://odrs.gnome.org/oars">an online form</a> which will automatically generate AppStream compatible markup based on a set of questions answered about the content.
</div><div class="para">
Example:
</div><pre class="programlisting"><span xmlns="" class="line"></span><span xmlns="" class="perl_Keyword"><content_rating</span><span xmlns="" class="perl_Others"> type=</span><span xmlns="" class="perl_String">"oars-1.0"</span><span xmlns="" class="perl_Keyword">></span>
<span xmlns="" class="line"></span> <span xmlns="" class="perl_Keyword"><content_attribute</span><span xmlns="" class="perl_Others"> id=</span><span xmlns="" class="perl_String">"drugs-alcohol"</span><span xmlns="" class="perl_Keyword">></span>moderate<span xmlns="" class="perl_Keyword"></content_attribute></span>
<span xmlns="" class="line"></span> <span xmlns="" class="perl_Keyword"><content_attribute</span><span xmlns="" class="perl_Others"> id=</span><span xmlns="" class="perl_String">"language-humor"</span><span xmlns="" class="perl_Keyword">></span>mild<span xmlns="" class="perl_Keyword"></content_attribute></span>
<span xmlns="" class="line"></span><span xmlns="" class="perl_Keyword"></content_rating></span></pre></dd></dl></div><div class="para">
An example for a very basic component file could look like this:
</div><pre class="programlisting"><span xmlns="" class="line"></span>
<span xmlns="" class="line"></span><span xmlns="" class="perl_Keyword"><?xml</span> version="1.0" encoding="UTF-8"<span xmlns="" class="perl_Keyword">?></span>
<span xmlns="" class="line"></span><span xmlns="" class="perl_Keyword"><component></span>
<span xmlns="" class="line"></span> <span xmlns="" class="perl_Keyword"><id></span>com.example.foobar<span xmlns="" class="perl_Keyword"></id></span>
<span xmlns="" class="line"></span> <span xmlns="" class="perl_Keyword"><name></span>Foo Bar<span xmlns="" class="perl_Keyword"></name></span>
<span xmlns="" class="line"></span> <span xmlns="" class="perl_Keyword"><summary></span>A foo-ish bar<span xmlns="" class="perl_Keyword"></summary></span>
<span xmlns="" class="line"></span> <span xmlns="" class="perl_Keyword"><url</span><span xmlns="" class="perl_Others"> type=</span><span xmlns="" class="perl_String">"homepage"</span><span xmlns="" class="perl_Keyword">></span>http://www.example.org<span xmlns="" class="perl_Keyword"></url></span>
<span xmlns="" class="line"></span> <span xmlns="" class="perl_Keyword"><metadata_license></span>CC0-1.0<span xmlns="" class="perl_Keyword"></metadata_license></span>
<span xmlns="" class="line"></span>
<span xmlns="" class="line"></span> <span xmlns="" class="perl_Keyword"><provides></span>
<span xmlns="" class="line"></span> <span xmlns="" class="perl_Keyword"><library></span>libfoobar.so.2<span xmlns="" class="perl_Keyword"></library></span>
<span xmlns="" class="line"></span> <span xmlns="" class="perl_Keyword"><font></span>foo.ttf<span xmlns="" class="perl_Keyword"></font></span>
<span xmlns="" class="line"></span> <span xmlns="" class="perl_Keyword"><binary></span>foobar<span xmlns="" class="perl_Keyword"></binary></span>
<span xmlns="" class="line"></span> <span xmlns="" class="perl_Keyword"></provides></span>
<span xmlns="" class="line"></span> <span xmlns="" class="perl_Keyword"><releases></span>
<span xmlns="" class="line"></span> <span xmlns="" class="perl_Keyword"><release</span><span xmlns="" class="perl_Others"> version=</span><span xmlns="" class="perl_String">"1.2"</span><span xmlns="" class="perl_Others"> date=</span><span xmlns="" class="perl_String">"2015-02-16"</span> <span xmlns="" class="perl_Keyword">/></span>
<span xmlns="" class="line"></span> <span xmlns="" class="perl_Keyword"></releases></span>
<span xmlns="" class="line"></span> <span xmlns="" class="perl_Keyword"><developer_name></span>FooBar Team<span xmlns="" class="perl_Keyword"></developer_name></span>
<span xmlns="" class="line"></span><span xmlns="" class="perl_Keyword"></component></span>
</pre><div class="para">
For a component of type <code class="literal">generic</code>, the minimal amount of required tags is: <a class="xref" href="chap-Metadata.html#tag-id-generic"><id/></a>, <a class="xref" href="chap-Metadata.html#tag-name"><name/></a>, <a class="xref" href="chap-Metadata.html#tag-summary"><summary/></a>, <a class="xref" href="chap-Metadata.html#tag-metadata_license"><metadata_license/></a>.
</div></div></div></div><ul class="docnav"><li class="previous"><a accesskey="p" href="chap-AppStream-About.html"><strong>Prev</strong>Chapter 1. About AppStream</a></li><li class="up"><a accesskey="u" href="#"><strong>Up</strong></a></li><li class="home"><a accesskey="h" href="index.html"><strong>Home</strong></a></li><li class="next"><a accesskey="n" href="sect-Metadata-Application.html"><strong>Next</strong>2.2. Desktop Applications</a></li></ul></body></html>
