See
http://www.xspf.org/xspf-v0.html#Definingplaylists - It seems that XSPF playlist format is the solution I've been looking for although I've now taken the advice on path on-board. Key info pasted below for reference. My question is then - does JRiver see the same problem and plan to accommodate in the future? Cheers, Mitch
Defining playlists
An XSPF playlist describes a sequence of objects to be rendered. Objects might be audio, video, text, playlists, or any other media type. The function of a playlist is to identify the objects and communicate their order.
What a playlist is not
The function of a playlist is not to communicate metadata about the composer, song title, etc. Metadata is hard and there are many providers already. We decided that we couldn't compete, and that there was no need for us to try. Moreover, good metadata does not travel well -- every user has to recreate it. Metadata should come from external sources and namespaces like MusicBrainz or Gracenote; this what the XSPF link and meta elements are for.
The function of a playlist is not to store derived information about objects that a user has a copy of. A playlist is not a catalog. A catalog is computed across hard data like files; it stores information like filesystem paths and the contents of ID3 tags. This data has no value on any machine but the one on which it originated. Sharing this data would be a privacy and security violation. Software which needs access to this data has no reason to maintain it in a standard format, because it has no reason to allow access to it. Standardizing this data would be fruitless, because there are an endless number of measurements that software might take and store. Derived information belongs in a catalog.
Things a playlist is not, then, are a metadata format or a catalog. We took care to enable these features, but also to avoid duplicating their functionality, poorly.
Shareability
If there is no reason for a playlist to be shared, there is no need for a new format. Even a buggy format does no damage if it is created and consumed by the same software on the same machine. The need for a new format only comes up when a playlist travels from one machine to another, for example when it is published on the internet.
One type of shareability is between different pieces of software on the same machine. It is common for playlists created with one application to not be usable by another application on the same machine because of different or conflicting interpretations of the playlist format. M3U suffers from this very badly, because M3U playlists often reference files according to a base path which changes from application to application. The XSPF group aimed to fix this by providing unambiguous definitions.
The other type of shareability is between different machines. For playlists to be meaningful on different machines, they must be able to identify network resources. Audio and video objects are often abstractions like "movie X by director Y" rather than computer-friendly objects like "whatever file can be gotten from the URL
http://foo/x/y". To handle this problem, we have provided support for media objects to be found via queries; XSPF identifiers are fuzzy names.