[ubl-cmsc] The "Phase 1 context methodology" proposal

["Eve L. Maler" <eve.maler@sun.com>]

I took an action to explain the proposal that I came up with for a Phase 
1 CM deliverable.  I'm also supposed to try to set up a CM telecon to 
keep the discussion going.  (There were other big CM developments last 
week as well...)  Matt, s'okay with you?  If so, here are the times I'm 
free in the coming few days; please respond with your own subset of 
these times and I would be happy to set up a phone call:

Fri 14 Jun: 7am-10am PT / 10am-1pm ET / 3-6pm UK / 4-7pm Eur
Mon 17 Jun: 7am-10am PT / 10am-1pm ET / 3-6pm UK / 4-7pm Eur
Tue 18 Jun: 7am-11am PT / 10am-2pm ET / 3-7pm UK / 4-8pm Eur
Thu 20 Jun: 9am-11am PT / 12n-2pm ET  / 5-7pm UK / 6-8pm Eur
Fri 14 Jun: 7am-10am PT / 10am-1pm ET / 3-6pm UK / 4-7pm Eur

Eventually I will have to write up the proposal properly (and give it a 
cutesie name; nothing has stuck yet :-), but I wanted to try and get the 
bare bones out there as soon as I could.  Here it is:

Summary:

. For Phase 1, do not yet enable the description of *deltas* between
   less-contextualized and more-contextualized types and schemas (context
   rules). Instead, enable merely the *description of the actual
   contexts* that apply to hand-derived schema modules built on top of
   UBL.  Allow these descriptions to be "defaulted" somehow for all types
   in a schema module, for ease/economy of context value assignment.

Consequences:

. Makes contextualized schemas stay strictly compliant with XSD
   derivation.  (And likely pushes us in this direction for future CM
   phases...)  Allows us not to have to re-solve all the problems that
   XSD currently solves, such as worrying about how to set the namespace
   of the constructs in the resulting contextualized schema.

. Pushes the work of generating derivations onto fairly knowledgeable
   schemographers.  (Since there are tools and tutorials extant for XSD
   work but not yet for context rules design, this doesn't seem like much
   of a cost.)

. Will probably encourage the creation of contextualized schemas
   overall, possibly resulting in a more confused picture of what modules
   get registered and what their relationships are to each other.
   However, getting this input will be a real win for our work on Phase
   2.

. Will result in the context descriptors for contextualized schemas and
   for the base UBL Library modules taking exactly the same form, which
   is nice.

Work to be done:

. We need to fully solve the general problem of documenting applicable
   contexts in order to allow hand-coders to add their context
   descriptions to their own types.  We discussed this at some length
   in the NDR meeting last week and made some progress.

. We need to figure out the defaulting rules of context descriptors that
   appear "globally" in the prolog of a schema module.  It must be
   possible at any time to "compute", given a stack of schema modules,
   the applicable context for any object class.

. We need to fully flesh out the rules for allowable contextualizations,
   much as XSD defines the rules for allowable derivations.  The context
   descriptors will be metadata on types that forms a phantom context
   hierarchy; what are the rules for context derivation?  Eduardo has
   already proposed one about properly specializing the context value
   hierarchy (see the NDR F2F minutes).  We will probably also need
   rules about computing from "additive" contexts (e.g.,
   geo="Americas+Asia") and ranges of contexts.

I would say that, if this proposal is acceptable to the fully 
constituted CM group, we need to produce this deliverable *fast* and we 
would need to promote it in much the same way as the code list 
recommendation, since both apply mostly to external producers and not 
just UBL proper.

A random observation: If formal mathematical comparison of XSD modules 
were easy to do, in the fashion that RELAX NG is amenable to this, then 
heck -- the context rules themselves could possibly be computed from the 
comparison of two contextually related schema modules!

BTW, I am taking cutesie name suggestions.

	Eve

-- 
Eve Maler                                    +1 781 442 3190
Sun Microsystems XML Technology Center   eve.maler @ sun.com