Update to specify escaping of colons, semicolons, and backslashes

[xdg-specs:xdg-specs.git] / specifications / FMPSpecs / specification.lyx

#LyX 1.6.7 created this file. For more info see http://www.lyx.org/
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\begin_body

\begin_layout Title
Free Media Player Specifications
\end_layout

\begin_layout Title
Tag Specification
\end_layout

\begin_layout Date
version 1.0; September 9, 2010
\end_layout

\begin_layout Author
Copyright 2009-2010 by 
\begin_inset Flex Element:Firstname
status collapsed

\begin_layout Plain Layout
Jeff
\end_layout

\end_inset

 
\begin_inset Flex Element:Surname
status collapsed

\begin_layout Plain Layout
Mitchell
\end_layout

\end_inset

 
\begin_inset CommandInset href
LatexCommand href
target "mitchell@kde.org"
type "mailto:"

\end_inset


\end_layout

\begin_layout Abstract
This specification describes various audio file tag metadata intended to
 increase interoperability between free music players for things such as
 ratings, playcounts, performer roles, and more.
 It does this by proposing standards for common functionality needs where
 none currently exist, and doing so in a way that is easily adoptable cross-play
er and cross-format.
 It is designed to be robust against future needs and to prevent possible
 conflicts with other tag identifiers and values.
\end_layout

\begin_layout Standard
\begin_inset CommandInset toc
LatexCommand tableofcontents

\end_inset


\end_layout

\begin_layout Section
Front Matter
\end_layout

\begin_layout Subsection
License
\end_layout

\begin_layout Standard
You may use this specification under either of the following licenses, at
 your discretion.
 Most will want to use it under Creative Commons; the GPL alternative is
 in case future versions of the spec contain e.g.
 code snippets that you would like to use in GPL programs:
\end_layout

\begin_layout Enumerate
This specification is licensed under the Creative Commons Attribution-Share
 Alike 3.0 Unported License.
 You are free to copy, distribute and transmit this work, provided that
 the copyright information and full URL to the license information page
 (
\begin_inset Flex URL
status collapsed

\begin_layout Plain Layout

http://creativecommons.org/licenses/by-nd/3.0/
\end_layout

\end_inset

) remain intact.
 If you alter, transform, or build upon this work, you may distribute the
 resulting work only under the same or similar license to this one.
 
\end_layout

\begin_layout Enumerate
This program is free software; you can redistribute it and/or modify it
 under the terms of the GNU General Public License as published by the Free
 Software Foundation; either version 2 of the License, or (at your option)
 any later version.
 This program is distributed in the hope that it will be useful, but WITHOUT
 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
 FOR A PARTICULAR PURPOSE.
 See the GNU General Public License for more details.
 See 
\begin_inset Flex URL
status collapsed

\begin_layout Plain Layout

http://www.gnu.org/licenses/
\end_layout

\end_inset

.
 
\end_layout

\begin_layout Subsection
Terminology
\end_layout

\begin_layout Standard
Terminology follws that specified in RFC2119, 
\begin_inset Quotes eld
\end_inset

Key words for use in RFCs to Indicate Requirement Levels
\begin_inset Quotes erd
\end_inset

.
 See 
\begin_inset Flex URL
status collapsed

\begin_layout Plain Layout

http://www.ietf.org/rfc/rfc2119.txt
\end_layout

\end_inset

 for more information.
\end_layout

\begin_layout Section
Audio Metadata Tags
\end_layout

\begin_layout Standard
The metadata tag formats evolved from Quod Libet's VorbisComments suggestions
 at 
\begin_inset Flex URL
status collapsed

\begin_layout Plain Layout

http://code.google.com/p/quodlibet/wiki/Specs_VorbisComments
\end_layout

\end_inset

, however this attempts to not only address ambiguities and incompatibilities
 with the specification at that URL, but also to define how this functionality
 should be applied across formats.
 It is intended that as usable ways of inserting the metadata described
 become available for formats not currently specified, that this document
 will be updated to meet those needs.
\end_layout

\begin_layout Standard
All newly-specified tags carry an identifier 
\begin_inset Quotes eld
\end_inset

FMPS_
\begin_inset Quotes erd
\end_inset

 to tie the tags to this specification.
 The reason is simple: since the official metadata specifications either
 fail to define or define unusable tags, these values are only official
 to the extent that this specification is adopted.
 Without an identifier to give context to the meanings and limitations of
 the values, there is a real possibility that a noncompliant media player
 will use the same tag names in an incompatible fashion, whether intentionally
 or not, and there is no way to determine whether a seemingly compatible
 use of the tags by a noncompliant player actually results in user-intended
 behavior.
 The 
\begin_inset Quotes eld
\end_inset

FMPS_
\begin_inset Quotes erd
\end_inset

 identifier and this specification document is therefore used in a similar
 fashion to XML schema declarations.
\end_layout

\begin_layout Standard
As these identifiers are read and modified only by players and advanced
 users, it is not expected to be a hindrance to adoption or to cause undue
 burden on either.
\end_layout

\begin_layout Subsection
Common Data and Tag Information
\end_layout

\begin_layout Standard
This section provides 
\begin_inset Quotes eld
\end_inset

up-front
\begin_inset Quotes erd
\end_inset

 information that is pertinent to all tags described below, such as what
 encoding to use and which tags to use in various formats.
\end_layout

\begin_layout Standard
For all tag formats, the following is defined:
\end_layout

\begin_layout Itemize
All identifiers are ASCII strings, and defined in the sections below.
 All identifier strings must escape each colon (':'), semicolon (';') and
 backslash ('
\backslash
') with a backslash.
\end_layout

\begin_layout Itemize
All values (including numeric values) are stored as strings, which MUST
 adhere to the allowed encoding and length limits in the relevant tag format
 specifications, but SHOULD use Unicode whenever possible.
\end_layout

\begin_deeper
\begin_layout Itemize
To keep the specification simple, no ranges of control characters are defined
 which should never be included in a string.
 It is assumed that the used string-handling library will properly handle
 any such characters encountered.
 It is highly recommended, however, that no such control characters are
 used, except when specified below.
\end_layout

\begin_layout Itemize
All value strings must escape each colon (':'), semicolon (';') and backslash
 ('
\backslash
') with a backslash.
 
\end_layout

\end_deeper
\begin_layout Itemize
Although identifier case is specified for the different types of tags, compariso
ns against identifier strings MUST be case-insensitive.
\end_layout

\begin_layout Itemize
A period/full stop is used to separate the digits in a float value from
 the fractional part of the float.
 All float values MUST include a period/full stop (1 is not acceptable;
 1.0 is correct).
\end_layout

\begin_layout Itemize
Float values SHOULD be limited to six decimal places.
\end_layout

\begin_layout Itemize
All lists are value strings.
 For any lists, entries MUST be separated with a double semicolon ';;' and
 fields within an entry MUST be separated with a double colon '::' (examples
 in following sections).
 These separation markers MUST NOT be escaped with backslashes.
 This allows for easy splitting of list entries and entry fields with most
 string libraries; the entries and fields can be split by double semicolon/doubl
e colon, and the ensuing fields can have any escaped values substituted.
\end_layout

\begin_layout Standard
The following sections describe where the information should be stored in
 specific tag formats.
\end_layout

\begin_layout Subsubsection
MP3
\end_layout

\begin_layout Standard
MP3 values MUST be stored in a TXXX frame with the Description set to the
 specified identifier and the Text set to the string representation of the
 value.
 The Description SHOULD be in CamelCase as specified in the following sections,
 e.g.
 FMPS_Rating.
\end_layout

\begin_layout Subsubsection
VorbisComments
\end_layout

\begin_layout Standard
Any file supporting VorbisComments (Vorbis, FLAC, Theora, Speex) MUST use
 a comment with the Key set to the specified identifier and the Value set
 to the string representation of the value.
 The Key SHOULD be in all upper-case, e.g.
 FMPS_RATING.
\end_layout

\begin_layout Subsubsection
APEv2
\end_layout

\begin_layout Standard
Any file supporting APEv2 MUST add a comment with the Key set to the specified
 identifier and the Value set to the string representation of the value.
 The Key SHOULD be in all upper-case, e.g.
 FMPS_RATING.
\end_layout

\begin_layout Subsubsection
MP4
\end_layout

\begin_layout Standard
MP4 values MUST be stored at ----:com.apple.iTunes:Identifier with the value
 a string representation of the tag's value.
 The Identifier SHOULD be in CamelCase as specified in the following sections,
 e.g.
 FMPS_Rating.
\end_layout

\begin_layout Subsubsection
Windows Media
\end_layout

\begin_layout Standard
Windows Media values MUST be stored in the FMPS/Identifier namespace with
 the value a string representation of the tag's value.
 The Identifier SHOULD be in CamelCase as specified in the following sections,
 e.g.
 FMPS_Rating.
\end_layout

\begin_layout Subsection
Rating Tags
\end_layout

\begin_layout Standard
Most media players support the notion of rating content, however standards
 for storing ratings in files do not exist.
 Some file metadata formats completely lack rating fields; others require
 personally identifiable information to be used as an identifier (such as
 a user's email address) or an organizational identifier (which reduces
 cross-player compatibility).
 The goal therefore is simple: to avoid any personally identifying information
 but to avoid tying the rating to a specific player.
\end_layout

\begin_layout Standard
Three types of ratings are currently defined: user ratings, critic ratings,
 and automatic (or algorithmic) ratings.
\end_layout

\begin_layout Standard
Although users are more naturally able to understand integer ratings, only
 advanced users will interact with these tags directly; otherwise they will
 be presented to the user via a conforming application.
 Meanwhile, there are tangible benefits to storing ratings as floating-point
 numbers, mainly due to the fact that the increased precision allows for
 a number of interesting and useful algorithmic rating schemes to be used.
 However, using both integer and floating-point values unnecessarily increases
 complexity of both this spec and application code.
 Therefore, both values are stored as floating-point numbers.
 Conversion to and from these and an integer scale presented to the user
 in an application is easily accomplished in the application's code if it
 is so desired.
\end_layout

\begin_layout Standard
Four tags are defined, corresponding to the three types of defined ratings,
 plus a canonical value: FMPS_Rating_User; FMPS_Rating_Critic; FMPS_Rating_Algor
ithm; and FMPS_Rating (the canonical value).
 A file that has no rating tag for a specific purpose is to be considered
 unrated for that purpose (user, critic or algorithm).
\end_layout

\begin_layout Subsubsection
All Rating Tags
\end_layout

\begin_layout Itemize
Ratings SHALL be a float value between 0.0 and 1.0, inclusive.
 0.0 SHALL be the lowest possible rating; 1.0 is the highest possible rating.
\end_layout

\begin_layout Itemize
Ratings SHOULD only be rounded when necessary, in order to increase cross-player
 compatibility.
\end_layout

\begin_layout Subsubsection
FMPS_Rating
\end_layout

\begin_layout Itemize
The canonical rating value in FMPS_Rating SHOULD be set whenever a user
 rates the track.
 This is in addition to any value stored for that particular user in FMPS_Rating
_User.
 This value is canonical because if a player does not support multiple users
 (or if no user identifier is set), this is the value that MUST be returned.
\end_layout

\begin_layout Itemize
If a user removes ratings from a track in the media player's database, the
 value of the FMPS_Rating tag SHOULD be cleared as well.
\end_layout

\begin_layout Subsubsection
FMPS_Rating_User
\end_layout

\begin_layout Itemize
If a player supports the notion of multiple users (perhaps from discovery
 of the current user from the operating system) and wishes to allow the
 users to keep separate ratings, it MUST store these values in the FMPS_Rating_U
ser tag.
\end_layout

\begin_layout Itemize
Applications supporting multiple user ratings SHOULD have a way for users
 to define their preferred identifier.
 
\end_layout

\begin_layout Itemize
The values are in the form of a list as defined in Section 2.1, with list
 entries in the format of UserIdentifier::Value.
 There MUST NOT be empty value strings.
\end_layout

\begin_layout Standard
Example: 
\begin_inset Quotes eld
\end_inset

Alice Abba::0.6;;Bob Beatles::0.8
\begin_inset Quotes erd
\end_inset

.
\end_layout

\begin_layout Subsection
FMPS_Rating_Critic
\end_layout

\begin_layout Itemize
The values MUST be in the form of a list as defined in Section 2.1, with
 list entries in the format of Publication::Critic::Rating.
 If the critic is unaffiliated, or if the rating is by a publication with
 no byline, the special value 
\begin_inset Quotes eld
\end_inset

FMPS_Nothing
\begin_inset Quotes erd
\end_inset

 MUST be used to denote this; there MUST NOT be empty strings.
\end_layout

\begin_layout Standard
Example: 
\begin_inset Quotes eld
\end_inset

Rolling Stone::Ralph Gleason::0.83;;musicOMH.com::FMPS_Nothing::0.76;;Metacritic::F
MPS_Nothing::0.8;;FMPS_Nothing::Some Dude::0.9
\begin_inset Quotes erd
\end_inset


\end_layout

\begin_layout Subsubsection
FMPS_Rating_Algorithm
\end_layout

\begin_layout Itemize
The values MUST be in the form of a list as defined in Section 2.1, with
 list entries in the format of Application::Algorithm::Rating.
 All fields MUST be defined; fields MUST NOT be left empty.
\end_layout

\begin_layout Itemize
In cases where the algorithm is intended to be global/collaborative/cross-applic
ation, the Application value SHOULD be set to some agreed-upon value.
 In other words, it is RECOMMENDED to use the application name for the Applicati
on part of the identifier, but it MAY also be used to identify a 
\begin_inset Quotes eld
\end_inset

group
\begin_inset Quotes erd
\end_inset

 of algorithms, or some arbitrary other value that can be used for identificatio
n.
\end_layout

\begin_layout Standard
Example: 
\begin_inset Quotes eld
\end_inset

Amarok::AutoRate::0.52;;VLC::Standard::0.6;;QuodLibet::RatingPlugin
\backslash
:X::0.35;;The Free Music Player Alliance::Rating Algorithm 1::0.5
\begin_inset Quotes erd
\end_inset


\end_layout

\begin_layout Standard
A note on the floating point values: some players may only allow users to
 rate in increments of whole numbers between 1 and 5; others 0 and 10; and
 so on.
 However, players SHOULD ensure that the rating they display and use for
 any purpose adheres to that saved in the tag whenever possible, only rounding
 this number when absolutely necessary.
\end_layout

\begin_layout Standard
For instance, if a track has a rating of 0.9 and an application only shows
 ratings using five star icons in full-star increments, this would be rounded
 within the application to five stars.
 Howeer, if the player also shows the rating numerically, the application
 would display 4.5 in the numeric field instead of the same 5 shown in the
 star icons, thus more accurately reflecting the user's set rating.
\end_layout

\begin_layout Subsection
Playcount Tags
\end_layout

\begin_layout Standard
As with ratings, there are multiple kinds of playcount tags (user and algorithmi
c) in addition to a canonical value.
 The user tag tracks how many times a song has been played for a user.
 The auto/algorithmic value can be used in an application-specific way to
 do interesting things; for instance, to cumulatively track exact percentages
 of tracks played, in order to display to the user the number of days/hous/minut
es/seconds they have spent listening to a particular song.
 
\end_layout

\begin_layout Standard
Three tags are defined, corresponding to the two types of defined playcounts,
 plus a canonical value: FMPS_Playcount_User; FMPS_Playcount_Algorithm;
 and FMPS_Playcount (the canonical value).
 A file that has no playcount tag for a specific purpose is to be considered
 unplayed for that purpose (user or algorithm).
\end_layout

\begin_layout Subsubsection
All Playcount Tags
\end_layout

\begin_layout Itemize
Playcounts MUST be a float value not less than 0.0.
 0.0 is valid and means unplayed.
\end_layout

\begin_layout Itemize
The maximum value SHALL be 0.000001 less than the largest value able to be
 stored in a 32-bit unsigned integer: 4,294,967,294.999999.
 This is so that playcount values can be rounded to an integer equivalent,
 if necessary (e.g.
 for display to the user).
\end_layout

\begin_layout Subsubsection
User Playcount Criteria
\end_layout

\begin_layout Standard
The user playcount isn't meant to be set by the user, but rather to follow
 these rules that define user behavior.
 A file is to be considered 
\begin_inset Quotes eld
\end_inset

played
\begin_inset Quotes erd
\end_inset

 if it meets the following criteria, inspired by Last.fm's scrobbling rules:
\end_layout

\begin_layout Itemize
If the track is less than thirty seconds long, the entire song MUST be played.
\end_layout

\begin_layout Itemize
If the track is more than thirty seconds long but less than eight minutes
 long, at least fifty percent of the file MUST be played, calculated via
 length of track.
 For instance, if a track is one minute long, at least thirty seconds of
 the track must have been played, although if the user skips backwards multiple
 times and listens to the same ten seconds of the track three times in a
 row, this may be considered a valid playcount.
\end_layout

\begin_layout Itemize
If the track is longer than eight minutes, at least four minutes of the
 track MUST be played.
\end_layout

\begin_layout Standard
User playcounts have an additional restriction in that they MUST be float
 values representing integers (1.0, 141.0, etc.).
 They are never fractional values; a song was either played, or it wasn't.
\end_layout

\begin_layout Subsubsection
FMPS_Playcount
\end_layout

\begin_layout Itemize
The canonical playcount value in FMPS_Playcount SHOULD be set whenever a
 user plays a track.
 This is in addition to any value stored for that user in FMPS_Playcount_User.
 This value is canonical because if a player does not support multiple users
 (or if no user identifier is set) this is the value that MUST be returned.
\end_layout

\begin_layout Itemize
If a user has an identifier set to store per-user playcounts, when this
 value is set it MUST be set to the value of that user's playcount.
 In other words, the last value held in FMPS_Playcount will be equivalent
 to the latest user's personal playcount, if any.
\end_layout

\begin_layout Itemize
If a user resets the playcount for a track in the media player's database,
 the value of the FMPS_Playcount tag SHOULD be cleared as well.
\end_layout

\begin_layout Itemize
FMPS_Playcount MUST store 
\begin_inset Quotes eld
\end_inset

full plays
\begin_inset Quotes erd
\end_inset

 of a track according to the rules in Section 2.4.2.
\end_layout

\begin_layout Subsubsection
FMPS_Playcount_User
\end_layout

\begin_layout Itemize
If a player supports the notion of multiple users (perhaps from discovery
 of the current user from the operating system) and wishes to allow the
 users to keep separate playcounts, it MUST store these values in the FMPS_Playc
ount_User tag.
\end_layout

\begin_layout Itemize
Applications supporting multiple user playcounts SHOULD have a way for users
 to define their preferred identifier.
 
\end_layout

\begin_layout Itemize
The values MUST be in the form of a list as defined in Section 2.1, with
 list entries in the format of UserIdentifier::Value.
 There MUST NOT be empty strings.
\end_layout

\begin_layout Itemize
FMPS_Playcount_User MUST store 
\begin_inset Quotes eld
\end_inset

full plays
\begin_inset Quotes erd
\end_inset

 of a track according to the rules in Section 2.4.2.
\end_layout

\begin_layout Standard
Example: 
\begin_inset Quotes eld
\end_inset

Alice Abba::1.0;;Bob Beatles::133.0
\begin_inset Quotes erd
\end_inset

.
\end_layout

\begin_layout Subsubsection
FMPS_Playcount_Algorithm
\end_layout

\begin_layout Itemize
The values MUST be in the form of a list as defined in Section 2.3.1, with
 list entries in the format of Application::Algorithm::Playcount.
 All fields MUST be defined; fields MUST NOT be left empty.
\end_layout

\begin_layout Itemize
In cases where the algorithm is intended to be global/collaborative/cross-applic
ation, the Application value SHOULD be set to some agreed-upon value.
 In other words, it is RECOMMENDED to use the application name for the Applicati
on part of the identifier, but it MAY also be used to identify a 
\begin_inset Quotes eld
\end_inset

group
\begin_inset Quotes erd
\end_inset

 of algorithms, or some arbitrary other value that can be used for identificatio
n.
\end_layout

\begin_layout Itemize
For algorithms, a track's length MUST be considered to be worth 1.0 playcounts;
 the user skipping parts of the track MAY decrease the value below 1.0, and
 the user repeating parts of the track MAY increase this value past 1.0.
\end_layout

\begin_layout Standard
Example: 
\begin_inset Quotes eld
\end_inset

Amarok::AutoPlaycount::152.69;;VLC::Standard::198.0;;QuodLibet::PlaycountPlugin
\backslash
:X::1652.19;;The Music Player Alliance::Playcount Algorithm 1::0.5
\begin_inset Quotes erd
\end_inset


\end_layout

\begin_layout Subsection
Performer Roles
\end_layout

\begin_layout Standard
Performer roles allow you to describe the performers in a track.
 Current support for these roles in tag formats is often sporadic or difficult
 to parse.
 As many of these tags as desired can be specified, to include all relevant
 performer information.
\end_layout

\begin_layout Itemize
Performer roles use the identifier 
\begin_inset Quotes eld
\end_inset

FMPS_Performers
\begin_inset Quotes erd
\end_inset

.
 The value MUST be a list in the form of Performer::Role, where Role is
 the user-defined role (
\begin_inset Quotes eld
\end_inset

Guitar
\begin_inset Quotes erd
\end_inset

, 
\begin_inset Quotes eld
\end_inset

Guitar (Backup)
\begin_inset Quotes erd
\end_inset

, 
\begin_inset Quotes eld
\end_inset

Vocals
\begin_inset Quotes erd
\end_inset

).
\end_layout

\begin_layout Standard
Example: 
\begin_inset Quotes eld
\end_inset

Willy Nelson::Guitar;;Eric Clapton::Guitar (Backup);;B.B.
 King::Vocals
\begin_inset Quotes erd
\end_inset


\end_layout

\begin_layout Subsection
Lyrics
\end_layout

\begin_layout Standard
Embedding lyrics into a file allows users to save custom lyrics and to still
 see the lyrics when not connected to the Internet.
 Since different users may wish to have different sets of lyrics (for example,
 if customizing lyrics against a music-only track) and different Internet
 sources may have different lyrics, it is possible to store multiple lyrics
 values by specifying a source.
\end_layout

\begin_layout Itemize
The identifier for the (canonical) lyrics text is 
\begin_inset Quotes eld
\end_inset

FMPS_Lyrics
\begin_inset Quotes erd
\end_inset

.
 The value MUST be a string.
 Spaces, tabs, and newlines SHOULD be preserved when saving the string,
 and SHOULD be displayed properly to the user.
\end_layout

\begin_layout Itemize
Lyrics MAY also be stored in FMPS_Lyrics_Sources as a list (as defined in
 Section 2.1), in which case the form MUST be Source::Data.
\end_layout

\begin_layout Standard
Example: 
\begin_inset Quotes eld
\end_inset

Alice Aardvark::[lyrics];;Bob Baboon::[lyrics];;http
\backslash
://www.lyricssite.net::[lyrics]
\begin_inset Quotes erd
\end_inset


\end_layout

\begin_layout Subsection
Album/Compilation (
\begin_inset Quotes eld
\end_inset

Various Artists
\begin_inset Quotes erd
\end_inset

) Identifier
\end_layout

\begin_layout Standard
Compilations (or 
\begin_inset Quotes eld
\end_inset

Various Artists
\begin_inset Quotes erd
\end_inset

 albums) can be difficult for music players to discover.
 Sometimes the user places all files from a compilation in one directory
 and expects that the music player will understand this; sometimes the user
 has them in different directories but with the same album name and expects
 that the music player will understand this; and so on.
\end_layout

\begin_layout Standard
Although there are existing solutions to identify albums and songs that
 belong to the same album (such as MusicBrainz identifiers) many users have
 not or do not want to tag their songs with MusicBrainz information.
 This tag therefore provides a simple way for an application to assign a
 album identifier to a track, indicating to what album a track belongs.
 It also provides a simple way of marking the album as a compilation or
 not.
\end_layout

\begin_layout Standard
This enables such use-cases as allowing a user to mark multiple tracks that
 are part of a single compilation, and then have those tracks show up as
 being together in a compilation the next time the user adds the tracks
 to the music player.
\end_layout

\begin_layout Standard
This section purposefully does not define information about the album/compilatio
n; it is expected that the user must supply that information in appropriate
 existing tags, e.g.
 ALBUM and ALBUMARTIST for VorbisComments.
\end_layout

\begin_layout Itemize
The identifier for the album/compilation tag is FMPS_Albums_Compilations.
 Although this tag will be most useful for compilation/Various Artists albums,
 there may still be significant utility for a player in using this tag to
 identify single-artist albums.
 As a result, players MUST NOT make assumptions about whether the presence
 of this tag identifies the track as belonging to a compilation/Various
 Artists album and MUST explicitly derive this information from the tag
 value.
\end_layout

\begin_layout Itemize
Values MUST be a list (as defined in Section 2.1) in the form of Application::Typ
e::Identifier.
 Applications MAY have more than one identifier, if the user wants to mark
 a track as being present in multiple compilations, or to give user-defined
 names to a compilation.
 However, each list entry MUST be unique.
 Similarly to other tags in this specification, there may be significant
 utility in interoperating on the application names.
\end_layout

\begin_layout Itemize
Type MUST be one of the following values, without quotes: 
\begin_inset Quotes eld
\end_inset

Album
\begin_inset Quotes erd
\end_inset

 (indicating a general-purpose album, usually by a single artist) or 
\begin_inset Quotes eld
\end_inset

Compilation
\begin_inset Quotes erd
\end_inset

 (indicating a compilation album, usually by multiple/various artists).
 Checks against this value MUST be case-insensitive.
 More values may be added in the future; if a player encounters an unknown
 value it SHOULD default to type 
\begin_inset Quotes eld
\end_inset

Album
\begin_inset Quotes erd
\end_inset

.
 
\end_layout

\begin_layout Standard
Example: 
\begin_inset Quotes eld
\end_inset

Amarok::Album::2982ab29ef;;AmarokUser::Compilation::My Compilation;;Banshee::Com
pilation::ad8slpbzl229zier;;FMPSAlliance::Album::de9f2c7fd25e1b3afad3e85a0bd17d9
b100db4b3
\begin_inset Quotes erd
\end_inset


\end_layout

\end_body
\end_document