XML Web Service v2
This is my proposal on how V2 of the XML_Web_Service should work. --warp.
NOTE: As of the beta 2 release on 2010-06-21, most of what is documented below has been implemented. Currently missing are the filters on release-group type and release status, if you want to know when this gets added, keep an eye on http://jira.musicbrainz.org/browse/MBS-686 . POST requests also haven't been implemented, and haven't been documented here. The ticket for those is http://jira.musicbrainz.org/browse/MBS-142 .
We have six resources on our web service which represent core entities in our database:
artist, label, recording, release, release-group, work
We also provide a web service interface for the following non-core resources:
rating, tag, collection
And we allow you to perform lookups based on other unique identifiers with these resources:
disc, puid, isrc, iswc
On each entity resource, you can perform three different GET requests:
lookup: /<ENTITY>/<MBID>?inc=<INC> browse: /<ENTITY>?<ENTITY>=<MBID>&limit=<LIMIT>&offset=<OFFSET>&inc=<INC> search: /<ENTITY>?query=<QUERY>&limit=<LIMIT>&offset=<OFFSET>
- Lookups, Non-MBID lookups and Browse requests are documented in following sections.
- Searches are implemented by the search server and are documented at Next_Generation_Schema/SearchServerXML.
- ratings, tags and collections are not currently documented for /ws/2.
You can perform a lookup of an entity when you have the MBID for that entity:
The inc= is parameter allows you to request more information to be included about the entity. Any of the entities directly linked to the entity can be included.
/ws/2/artist recordings, releases, release-groups, works /ws/2/label releases /ws/2/recording artist, releases /ws/2/release artist, label, recordings, release-groups /ws/2/release-group artist, releases /ws/2/work artist
All lookups which include release-groups allow a type= argument to narrow down the release-groups. All lookups which include releases also allow the type= argument, and a status= argument is allowed.
Note that the number of linked entities returned is always limited to 25, if you need the remaining results, you will have to perform a browse request.
inc= arguments which affect subqueries
Some additional inc= parameters are supported to specify how much of the data about the linked entities should be included:
- discids include discids for all media in the releases - media include media for all releases, this includes the # of tracks on each medium. - puids include puids for all recordings - isrcs include isrcs for all recordings - artist-credits include artists credits for all releases and recordings - various-artists include only those releases where the artist appears on one of the tracks, but not in the artist credit for the release itself (this is only valid on a /ws/2/artist?inc=releases request).
Misc inc= arguments
- aliases include artist, label or work aliases
inc= arguments to include relationships work exactly like they do in /ws/1:
- artist-rels - label-rels - recording-rels - release-rels - release-group-rels - url-rels - work-rels
Instead of MBIDs, you can also perform lookups using several other unique identifiers. However, because clashes sometimes occur, each of these lookups return a list of entities (there is no limit, all linked entities will be returned, paging is not supported).
A discid lookup returns a list of associated releases, the 'inc=' arguments supported are identical to a lookup request for a release.
lookup: /puid/<puid>?inc=<INC> lookup: /isrc/<isrc>?inc=<INC>
puid and isrc lookups return a list of recordings, the 'inc=' arguments supported are identical to a lookup request for a recording.
An iswc lookup returns a list of works, the 'inc=' arguments supported are identical to a lookup request for a work.
Browse requests are a direct lookup of all the entities directly linked to another entity. (with directly linked I am referring to any relationship inherent in the database, so no ARs). For example, you may want to see all releases on netlabel ubiktune:
Note that browse requests are not searches, in order to browse all the releases on the ubiktune label you will need to know the MBID of ubiktune.
The following list shows which linked entities you can use in a browse request:
/ws/2/artist recording, release, release-group, work /ws/2/label release /ws/2/recording artist, release /ws/2/release artist, label, recording, release-group /ws/2/release-group artist, release /ws/2/work artist
As a special case, release also allows track_artist, which is intended to allow you to browse various artist appearances for an artist. It will return any release where the artist appears in the artist_credit for a track, but NOT in the artist_credit for the entire release (as those would already have been returned in a request with artist=<MBID>).
- 〜 I think track_artist as described above is important, otherwise you will get client software requesting all recordings for an artist, followed by release requests for each of the recordings found earlier. --warp.
Release-groups can be filtered on type, and releases can be filtered on type and/or status. For example, if you want all the Live Bootleg releases by Metallica:
Or all albums and EPs by Autechre:
Note that filtering is mandatory, if you don't specify type or status the release and release-group resources will not return any results.
Browse requests are the only requests which support paging, any browse request supports an 'offset=' argument to get more results. Browse requests also support 'limit=', the default limit is 25, and you can increase that up to 100.
Just like with normal lookup requests, the server can be instructed to include more data about the entity using an 'inc=' argument. Supported values for inc= are:
/ws/2/artist aliases /ws/2/label aliases /ws/2/recording artist-credits /ws/2/release artist-credits, labels /ws/2/release-group artist-credits /ws/2/work artist-credits, aliases
In addition to the inc= values listed above, all entities (except release) support:
tags, ratings, user-tags, user-ratings
- 〜 we probably want to allow a few more inc= arguments here, though we can always add more later. --warp.
Release Type and Status
Certain lookup and browse requests allow you to filter the returned releases on release group type and release status. Valid values are:
status official, promotion, bootleg, pseudo-release type nat, album, single, ep, compilation, soundtrack, spokenword, interview, audiobook, live, remix, other