Joern Nettingsmeier wrote:
[...]
1) Backwards compatibility
Since meta data are stored with the content, they must either
be stable, or there must be a migration tool.
that's what i was aiming at: if we introduce modular, arbitraty
metadata, it should still be clear which is "core", meaning: for these
fields the maintainers will take care of backwards compatibility or
provide a migration tool.
Where should this information be available?
Isn't it sufficient that these meta data are declared by the core?
2) Protection
Maybe some meta data should be read-only, or only accessible from
certain components.
important point. i hadn't thought of that...
that implies we should have a central component that handles all
metadata operations - i'm not familiar with the code, perhaps that is
already the case?
At the moment, there are separate classes for different meta data.
IMO this polymorphism should be replaced by configuration, and all
meta data should be handled by a single component.
3) Validation
It should be possible to define additional meta data sets which are
used by custom components. The meta data should be validated, i.e.
the set of keys is fixed.
hmmm. i don't understand. either the set of keys is fixed, or it's
possible to define addtional data sets... can you explain?
From my point of view, meta data can be organized in sets.
A set is identified by a namespace.
Lenya should allow to declare sets, each of which has a
well-defined set of elements. New core components and custom
components wouldn't have to extend the existing sets, but could
introduce new sets. The key sets of the existing sets wouln't
have to be changed.
For each set, the common meta data component could check if
a key exists, if a key supports multiple values etc.
Some Lenya core sets are:
DublinCoreTerms dc:creator, dc:title, ...
DublinCoreElements dcterms:contributor, dcterms:coverage, ...
DocumentMetaData resourceType, sourceExtension, ...
WorkflowMetaData version
Custom sets could be
MuseumMetaData painter, year, technique, ...
BicycleMetaData manufacturer, no. of gears, ...
I hope this explains what I mean,
-- Andreas
--
Andreas Hartmann
Wyona Inc. - Open Source Content Management - Apache Lenya
http://www.wyona.com http://lenya.apache.org
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