ZedDist Profiles Universal Fallback
From zedwiki
This is a landing page page for proposals on the Generic Fallback Mechanism target of ZedDist profiles. It is part of the architecture groups' inception activity, and will eventually contain a finalized proposal.
This page is under construction
Contents |
Rationale
A profile fallback mechanism, as discussed in ZedDist_Profiles is employed to maintain reading device compatibility in a context where multiple DTB profiles are being distributed.
Solution proposals
1. Container-level fallback
In a container-level fallback solution, the distributed examplar can manifest itself in multiple guises to a reading device. The individual guises are uncluttered (in other words: no inlined fallbacks; everything happens at the container level).
- In a document type similar in nature to the z2002/2005 distinfo document type, several package files are identified, each identifying the same publication but in a different guise;
- These share the same media objects where applicable, thus (at least in the cases where large binaries such as audio and video are involved) having only a minimal impact on the distribution size;
- The reading device, being itself aware which profiles it supports, picks the appropriate entry, and continues as usual.
Additional aspects/questions of this approach:
- This can also be used to identify non-z3986 guises (say, mp3 playlist formats alongside the z3986 lightweight audio profile)
- What happens if a reading device supports multiple of the guises provided? The new distinfo file must be able to express a preference hierarchy?
2. Manifest-level fallback
This provides a fallback for an individual file within the fileset of a guise. The OPF fallback mechanism may be all we need.
Can/should be used in conjunction with Container-level fallback.
