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unify fields and tags

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Joey Hess 2014-02-11 16:27:27 -04:00
parent faed5d3cc2
commit b7ffe599e8
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1 changed files with 7 additions and 14 deletions
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doc/design/metadata.mdwn
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@ -2,16 +2,14 @@
# metadata
Attach an arbitrary set of metadata to a key.
Attach an arbitrary set of metadata to a key. This consists of any number
of fields. Each field has an unordered set of values. The special field
"tag" has as its values any tags that are set for the key.
Store in git-annex branch, next to location log files.
Metadata can be tags, but it can also be fields with values (ie, date=xxx,
conference=yyy). Fields can have multiple values, for example
multiple authors.
Storage needs to support union merging, including removing tags, and
changing values.
Storage needs to support union merging, including removing an old value
of a field, and adding a new value of a field.
## automatically added metadata
@ -33,9 +31,6 @@ metadata is derived, at least year=yyyy and probably also month, etc.
This is probably not stored anywhere. It's computed on demand by a pure
function from the other metadata.
From the set of tags a file has, a "tag" field is derived, which has the
value of each tag. See example below.
Should be a general mechanism for this. (It probably generalizes to
sql queries if we want to go that far.)
@ -65,10 +60,8 @@ filtered/year=2012,2013,2014/talk/conference=fosdem,icfp. Now there
are nested subdirectories. They follow the format of the branch,
so 2013/icfp, 2014/fosdem, etc.
`git annex filter tag=haskell,debian` uses the "tag" field that is
automatically derived from the set of tags. So this yields a branch
with haskell and debian subdirectories, containing the files tagged with
either.
`git annex filter tag=haskell,debian` yields a branch with haskell
and debian subdirectories.
To see all tags, `git annex filter tag=*` !