On Dec 30, 2008, at 8:33 PM, Antony Blakey wrote:
On 30/12/2008, at 1:40 AM, Robert Dionne wrote:
With respect to a meta structure, I was going to make this comment
yesterday as I think Geir was arguing for this:
It seems to me that occam's razor argues for the simplicity of a
single JSON doc, rather that a "metadoc" envelope that contains
another JSON doc embedded in it. It's not clear to me that
creating this separation of concerns buys anything at all. The use
of an underscore to designate distinguished fields at the top
level is a fairly easy convention to get your arms around.
That's not actually the issue. The issue is about having a single
name, and not inventing a namespace technique for json docs. The
choices are:
I understand the issue. I noted the use of _id versus id myself and
wasn't that put off by it, just seemed a quirk of the implementation.
I realize you've likely written a lot of code a this point and have
run into reuse issues. It's not unusual to have different names for
the same thing if the context is different.
1. The current scheme of prepending _ to atom names when the atom
is used inside a document. Con is the breakage of name identity,
which has technical consequences as well as cognitive ones. Does
the rule only apply at the top level of a document? What about
future injected metadata that has internal structure?
2. Use '_' for all atoms, inside and outside documents. Con is the
noise of extra underscores everywhere.
3. Don't use underscores inside documents - for id and rev at
least, this wouldn't seem to be a big issue, but isn't future-proof
if you want to handle other injected fields.
4. Use '_' for atoms that have to be injected, and make the name BE
the '_' form. Con is that you have to decide in advance if an atom
is going to ever be injected.
5. Use a '_meta' wrapper for the metadata. I don't see any
technical cons, and IMO is by far the cleanest model. Name identity
is preserved, it's arbitrarily extensible without scalability
concerns, and is structural rather than lexical.
It is clearly cleaner and has it's advantages, however I have to
agree with an earlier poster; "Putting them in a _meta group might
encourage aggregation and manipulation of the bookkeeping metadata
separately from the document, which to me sounds like a recipe for
trouble."
This would be a more complex design than the current use of the
underscore at the top level of documents and would definitely
encourage a quite different implementation. I don't know the
internals enough yet to comment on this. The code there to date is
remarkably terse for what it does but this may just reflect the use
of Erlang.
Cheers,
Bob
IMO option 5 is the best and cleanest solution.
Antony Blakey
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