I'm no expert in SQL data types, but does a table like this help the
discussion along?
http://wiki.osafoundation.org/bin/view/Projects/
ExternalInformationModelDataTypes
The leftmost column contains the types supported by application/
schema.py. The middle column could get filled in with whatever types
Cosmo supports. The rightmost column are guesses at some SQL types
based on the MySQL documentation.
On Sep 12, 2006, at 12:31 PM, Phillip J. Eby wrote:
I'd like for us to meet on Thursday, September 14th, at 3pm PST to
discuss the type system for the sharing external information model
between Chandler and Cosmo. Morgen and Brian Moseley have both
proposed using XSD, but I think we need to narrow the field a
little, since XSD is much broader than what either the Chandler or
Cosmo backends can actually accept at this point in time. So, I
don't field comfortable making the spec allow you to just throw in
there whatever types XSD allows. We should at least narrow it down
to the subset of XSD that each backend can comfortably support,
even if we use the XSD model for specifying types.
However, we could also just as easily use a very strict concrete
typing based on SQL types, or just list out what types and
variations thereof we will allow in the current version, and how we
will communicate that type information.
So the first goal of the meeting is to decide "what types we care
about", in the sense of both the specific types themselves, and
what *distinctions* between types are necessary. For example, the
Chandler repository doesn't care about how big a Text field is, but
SQL databases usually do, and often make a distinction between
short text and long "memo" types at a smaller size than one would
usually care about in Chandler before switching to a blob type.
Another similar distinction is numeric precision, since SQL
databases tend to use fixed decimal places to describe their
numeric types, vs. the way Python and Java effectively use numbers
of bits.
So, we should establish what distinctions are critical, and then
from there decide whether to use an XSD subset, an SQL-like type/
precision notation, a fixed set of predefined types without any
variation allowed, or something else altogether.
Of course, if we can answer these questions via email before
Thursday and don't have to have a meeting, that's even better. :)
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