Item (a) is not mutually exclusive, as actually at
some point both are needed, I see a single data model and multiple description
languages.
Anthony Nadalin | Work 512.838.0085 | Cell 512.289.4122
"Jim
Sermersheim" <jimse@xxxxxxxxxx>
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"Jim
Sermersheim" <jimse@xxxxxxxxxx>
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Subject
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Re: [higgins-dev]
Revised Higgins data model goals
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9
and 10 talk about schema, and seem to say this:
a) Some schema data model or description language
is desired
b) Schema is tied to a Context, and is applied to
everything in that
Context (I'm inferring this)
c) Objects (I assume we're talking about
DigitalSubjects) have a
governing schema description
c.1) An object's schema description governs the
data allowed/required
to exist on the object
Beyond that, this is not mentioned:
d) Schema descriptors may apply to data elements
of an object
(attributes/relationships). In other words, schema
descriptors can be
used to govern certain aspects of data. i.e. a SSN
may only hold one
value, a surname may hold multiple values.
I'm inclined to envision how some of these goals
turn into reality in
my head, and then argue against the picture I see.
I agree with (a) above.
I disagree with (b). It seems unreasonable to tie
everything in a
Context to a fixed set of schema descriptors,
especially where a Context
may be fabricated from the conglomeration of
disparate data sources or
other Contexts.
I think (c) is fine as long as an object may be
governed by an "any"
schema descriptor. When this happens, an
application should be able to
enumerate and examine each element that makes up
the object (rather than
using a-priori knowledge of what it expects to be
there).
I assume that the schema governing an object's
data elements
(attributes/relationships), is discoverable given
that element's
identifier. In other words, an application can see
an identifier like
xyz://foo/bar/surname and know how to
access/display its data either by
some hard-coded knowledge of the
"surname" schema descriptor, or by
looking up the "surname" schema
descriptor and discovering things like
form, sub-elements, allowed meta-data,
multiplicity, yada yada.
I also assume that the schema governing an
object's data elements
(attributes/relationships) is independent of the
schema governing the
object which holds it. In other words, a
xyz://foo/bar/country element
behaves the same whether its held on a person
object or a device
object.
Is there a goal in terms of the access of schema?
I mean, I see two
possibilities: 1) Schema is accessed via a Context
or the objects held
with in the Context. 2) Schema is accessed
externally (by following the
identifier's URL, and read using some external
protocol like HTTP). I
think the goals are implying #1
Jim
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