- From: <paul.downey@bt.com>
- Date: Sun, 12 Mar 2006 22:17:50 -0000
- To: <public-xsd-databinding@w3.org>
Draft minutes from the Cannes F2F:
http://www.w3.org/2002/ws/databinding/6/3/F2F-databinding-minutes.html
and below for tracker's searching ..
W3C
- DRAFT -
XML Schema Patterns for Databinding WG F2F
27-28 February 2006
W3C Technical Plenary, Cannes-Mandelieu La-Napoule
Agenda
See also: IRC log: Monday, Tuesday
Log is incomplete due to networking issues.
Attendees
Present
Paul Downey (BT)
Jon Calladine (BT)
Yves Lafon (W3C)
Observers Present for part of meeting:
Philippe Le Hégare (W3C)
David Ezell (NACS)
Paul Thorpe (OSS Nokalva)
Michael Sperberg-McQueen (W3C)
Carine Bournez (W3C)
Regrets
Chair
pauld
Scribe
pauld
Contents
* Monday
1. Administrivia
2. How we work
3. ISSUE-4 - Collection of Databinding Implementations
4. ISSUE-1 - Scope of structures to be addressed
5. ISSUE-12 - Identifying a conformant schema
6. ISSUE-16 - Multiple patterns for a single data structure
7. ISSUE-2 - WSDL and the Test Suite
8. How we work, Redux
9. ISSUE-10 - mapping element and type names
10. ISSUE-19: Advice against using the 'all' model group
11. ISSUE-7 xsi:nil and minOccurs=0
Tuesday
1. ISSUE-17 - Advice for representing a duration
2. ISSUE-23 - Use of Mixed Content datatype
3. ISSUE-18 - Schema Authoring Style
4. ISSUE-13 and ISSUE-14 - xs:default handling by generated types
5. ISSUE-8 - Using patterns to constrain numerical types
6. ISSUE-20 - Extension of collections
7. ISSUE-7 - xsi:nil and minOccurs=0 xsi:nil, Redux
8. ISSUE-15 - ASN.1 null datatype
9. General ways forward
* Summary of Action Items
trackbot, init
<trackbot> Tracking ISSUEs and ACTIONs from http://www.w3.org/2005/06/tracker/databinding/
trackbot, start meeting
<trackbot> Date: 27 February 2006
Administrivia
discussion about participation, goals for this meeting
pauld: want's to document 'state of the art' in Basic patterns and work towards an interop fest during CR, later this year
discussion on roadmap
pauld: would like to identify schema features used by each document
... will enumerate 'features'
discussion of process, low participation is a worry from a 'mindshare' pov. we do have some people on the list who are adding value
pauld: basic patterns is really aimed at schema authors - here's what works well now with 'mainstream' tools
... 'mainstream' is a loaded term
... advanced is aimed at implementers. We have few implementers in the working group
<scribe> ACTION: pdowney to enumerate schema 'features' for the roadmap [recorded in http://www.w3.org/2006/02/27-databinding-minutes.html#action01]
<trackbot> Created ACTION-17 - Enumerate schema \'features\' for the roadmap [on Paul Downey - due 2006-03-06].
jonc:identification of patterns - we need to enlist help from schema gurus
How we work
Philippe joins us and we discuss how we can make progress
in essence we are doing unglamerous QA work
it's tough at the bottom :)
<Yves> http://www.w3.org/2005/06/tracker/databinding/issues/4
pauld: issues list is member visible
<scribe> ACTION: yves to write a wget script to publish issues on the public page [recorded in http://www.w3.org/2006/02/27-databinding-minutes.html#action02]
<trackbot> Created ACTION-18 - Write a wget script to publish issues on the public page [on Yves Lafon - due 2006-03-06].
ISSUE-4 - Collection of Databinding Implementations
pauld: suggest writing a small XSLT to rebuild Schema WG list
yves: and the subset is a list within the world of Web services
<scribe> ACTION: pdowney to build list of implementations [recorded in http://www.w3.org/2006/02/27-databinding-minutes.html#action03]
<trackbot> Created ACTION-19 - Build list of implementations [on Paul Downey - due 2006-03-06].
yves: flag list to SOAPbuilders
pauld: missing tools should ping us
ISSUE-1 Scope of structures
http://www.w3.org/2005/06/tracker/databinding/issues/1
discussion on mapping specific data structures - a pattern for vector doesn't have to be represented as a vector
not in business of saying this pattern MUST be presented as 'a vector' in all toolkits
pauld: or specifying turn-round patterns
document contains three sections - issues, schema patterns and data stuctures
Philippe: don't forget you can publish versions of a Rec 1.0, 1.1, etc
... what about testing this section
pauld: we can't test how each pattern is represented internally
discussion of echo test
pauld: test consists schema, schema instance, echo input document, toolkit desrialises, then serialises, client compares infosets
Philippe: sounds like you could re-use ws-addressing CR test suite
discussion of xs:any and how that might imact 'the bar' for basic patterns
ISSUE-12 identifying a conformant schema
<Yves> http://www.w3.org/2005/06/tracker/databinding/issues/12
<Yves> let's produce one using xslt and close the issue
<Philippe> W3C can host XSLT validation service
ISSUE-16 - Multiple patterns for a single data structure
RESOLUTION: first version of Basic patterns will not include quantification, may be added in later versions
ISSUE-2 - WSDL and the Test Suite
we could take schemas from the wild and identify elements, but more likely to create feature based testing
requires work one schema per pattern, we can build one WSDL per pattern or one 'mother or all
WSDLs' for all of the patterns
How we work, Redux
discussion of anti-patterns
testsuite, again
dezell: rather then just echo, how about an 'operation', e.g add two numbers, count elements, concat type values
discussion of pattern checker
dezell: maybe you could look ar XQuery as well as XSLT
.. declarative XML processing language
.. in 'selling' mode, so may be able to offer resource!
<Yves> Agenda: http://lists.w3.org/Archives/Public/public-xsd-databinding/2006Feb/0046.html
ISSUE-10 - mapping element and type names
pauld: introduces the issue
dezell: programing language to programming language is one problem
... xml is the superset? are there characters in programming languages not allowed in XML?
pauld: perl names begin with $, @, % etc
... NCName ::= (Letter | '_') (NCNameChar)*
... will recommending developers can using any XML NCName for elements and types give 'good experience' with 'state of the union' toolkits?
... recommending schema authors stick to US-ASCII would work best with C programming languge, but as a W3C WG, we can't go against i18n
yves: even if we allowed japanese variable names, it wouldn't help non-japanses programmers
... we could add text to say 'consider the audience of your schemas'
jonc: protect ourselves with that statement, but guarentee US-ASCII
pauld: worry about hand waving, when Kanji element names won't give 'good experience' with many tools
... maybe a 'warning' from the test suite, would be good enough
yves: not even US-ASCII - alphanumeric, not CR, LF, + * @ etc
dezell: we should say there is a general purpose mechanism, but we should also allow to advise a subset
RESOLUTION: ISSUE-6 closed, will use same text as ISSUE-10
ISSUE-19: Advice against using the 'all' model group
dezell: sequence should be used
- when you care about order of elements,
- and when you don't care!
... 'all' otoh is useful when order has meaning, i.e. 'a' before 'b' is different in meaning to 'b' 'a'
pauld: brilliant!, but cites example of reflection of Java class
dezell: can databinding tools keep a record of the schema defined sequence
... schema 1.1 working group working on the 'all' issue
... is it better to put the burdon of ordering on the sender or the receiver?
jonc: sender is usually best, e.g. receiver may not be schema aware
pauld: surely it 'depends', cites XDR (v) IDL 'sender makes good' (v) receiver makes good
dezell: ordering is useful, lack of ordering can lead to interoperability and can provide a processing burdon
... sees providing a default value as being closely related
jonc: would like all default values to be filled in ahead
dezell: many in the schema WG would agree with you
pauld: are we suggesting 'all' doesn't appear in our basic patterns?
yves: well, everything is ordered in memory
jonc: do toolkits generate 'all'?
pauld: not sure
<scribe> ACTION: jcalladi to report on code-first experiences with 'all' and toolkits [recorded in http://www.w3.org/2006/02/27-databinding-minutes.html#action05]
<trackbot> Created ACTION-21 - Report on code-first experiences with \'all\' and toolkits [on Jonathan Calladine - due 2006-03-06].
<trackbot> Tracking ISSUEs and ACTIONs from http://www.w3.org/2005/06/tracker/databinding/
let's go to break - back at 15:45 to talk about xsi:nil
ISSUE-7 xsi:nil and minOccurs=0
dezell: rec stands on its own, but can offer context for nil in the language
... distinction between absence of an element and null value - null is 'infectious'
... designation as null or nil, expresses half-hearted deprecation of data
jonc: paul biron has differences between not knowing and not existing
pauld:let's drill down into combinations http://www.flickr.com/photos/psd/111538769/in/set-72057594072218284/
minOccurs/nillable FALSE TRUE
0 OK AMBIGUOUS
=1 OK OK
>1 OK OK
dezell: analogous to floating point and NaN
... it's purely semantics
yves: should we document the background?
discussion of history .. nil is mea culpa in the document, not here means "not here"
jonc: minOccurs="0" nillable="true" does at least help mask toolkits which send nil regardless of the schema
pauld: let's work on the minOccurs/nillable truth table
dezell: are you sanctioning what works over best practice?
... XML Schema says little on the semantics of xsi:nil
... spec allows attibutes on a nil='true' element!!!
yves: use-case of an empty vector over no vector at all
pauld: maybe we could allow all combinations, but document avoiding 'nillable="true"/minOccurs="0"' as not being goood practice
dezell: noodles on yve's use-case ; we could advicate against the bad practice
... how do we get interoperability, even in a dark corner - do we say what each case "means"?
yves: can I craft a counter example to demonstrate the interop issue? I can try to produce something based upon the vector example
<scribe> ACTION: yves to craft vector counter example for ISSUE-7
<trackbot> Created ACTION-22 - Craft vector counter example for ISSUE-7 [on Yves Lafon - due 2006-03-06].
pauld: decision we have to make surrounds minOccurs=0 and nillable=true. Do we a) include it in BASIC patterns b) if we include it, do we add advice to avoid it
dezell: I would only cite nillable='true' on simple content
pauld: sounds like an excellent suggestion
... worry about the effect on the fixed array of objects use-case
dezell: suggests adding conservative on sending, liberal on reception rule at start of document
paud: Postel's law
yves: HTML horror!
<scribe> ACTION: jcalladi to craft text for ISSUE-7, table followed by 'best practice' against using nil minOccurs=0 and nillable
dezell: xsi:type in combination with a union makes sense
ISSUE-5 and ISSUE-9
move both issues to advanced patterns
ISSUE-23 Use of Mixed Content datatype
pauld: what does it 'mean' (to a toolkit) to say mixed='true'
msmq: likely to be handed a DOM, what does a DOM mean to an OO developer
yves: it's generic, and lacks types
pauld: essence of schema is adding types, I could imagine being given a PSVI annotated DOM node as being useful
msmq: natural language prose, XML allows me to add in phrase level annotations, tagging data would then give me a bag of typed data
pauld: were trying to document the art of the possible, my experience is tools bail when they hit mixed
dezell: by bail you mean drop to DOM
pauld: yes, (on a good day). We're not seeing 'strings' containing objects
ISSUE-17 - Advice for representing a duration
dezell: schema 1.1 working group looking at calculation of duration from two datetime values. Unambiguous representations. We took out leap seconds from calculations.
pauld: do people have good experiences using xs:duration
dezell: XSQuery has shaken a lot of the bugs out of this area
... a combination of a duration and a datetime isn't ambiguous
pauld: ws-addressing chose to use longInteger seconds
yves: documenting in BASIC that a duration is best represented
as a whole number of units: minutes, seconds, hours, years
dezell: derivative types of xs:duration works
ednote work taking place in XML Schema 1.1 WG
ISSUE-23 - Use of Mixed Content datatype
dezell: what do we do about sending HTML, mixed='true'
pauld: escaping seems attractive to many
yves: they base64 encode it!
discussion of appealing to i18n, markup may be required
for right to left.
pauld: cites ws-addressing log file use-case where BOM and
encoding caused problems, but saw great value in keeping contained XML as XML
msmq: proposition - suggest mixed content drops to DOM, should be easy to implement
discussion of mixed content use-cases
yves: basic patterns is documenting state of the art
jonc: we have recent experience with a mainstream SIP server which rejects schemas that contain mixed, anywhere
dezell: tentative solution is not to include it in the BASIC patterns
pauld: for me mixed is key to XML, it's saying a node contains XML
want to say something, even if it's an anti-pattern
discussion around anti-patterns, what's so special about mixed?
dezell: 'indictment', Advanced could be seen as 'ammunition'
pauld: I see this is like the name mapping - we have to document 'what works' but what works is so abhorrent we have to document what SHOULD work and say 'buyer beware'
msmq: draws attention to Henry's sample collection 1023 schemas 133 contain 'mixed'
yves: not many of those are likely to be databinding
dezell: would bet most of those are to escape HTML
<scribe> ACTION: msmq to report on status of Schema Collection
RESOLUTION: close ISSUE-23 with advice that tools should support mixed as a DOM node, but YMMV
ISSUE-18 - Schema Authoring Style
discussion of venetian (v) russian doll, salami slice akin to a DTD.
how Java inner and anonymous types may be represented
jonc: BT best practice has been to use venetian blind
pauld: worries this may be out of date, we need to do some work with recent versions of tools
<scribe> ACTION: pauld to investigate tools with authoring styles
ISSUE-13 and ISSUE-14 - xs:default handling by generated types
msmq: if validation was faster, wouldn't people use it all the time?
yves: it's seen as being redundant as processing the data model adds checking
pauld: issue falls into two parts: xs:default (v) other features
discussion around sender / receiver performing validation and completing default values
pauld: I have a schema with 500 optional/default values, my 80 point is sending 5 values in a message, xs:default seems useful
msmq: topnode validation at least, seems like an obvious, minimal requirement to me, mapping to objects seems to have the opportunity to perform validation. making it survive invalid documents seems like more work.
dezell: error reporting seems implementation dependent
... statement "for interoperability, all documents MUST be schema valid"
msmq: Mary is interested in partial validity
pauld: versioning is to be discussed this afternoon, and that's a good use-case for partial validity. Can't we say "SHOULD"
dezell: MUST seems to be state of the art
pauld: hears three issues here: xs:default (we've drilled into) and partial validation (state of the art seems seems to be strict validation) and the versioning use-case (possibly advanced patterns)
... seems like we're in need of some understanding of how tools handle xs:default in the wild
dezell: 'skip' and 'lax' seems to build upon PSVI
msmq: 'skip' seems to be a drop to DOM
dezel: is there a Web services use-case for lax and skip?
msmq: versioning?
jonc: we have a use-case with WS-Notification - cites use-case
discussion of lax and strict and wrapping
pauld: sounds like an implicit choice, an xsi:type even
jonc: it's not my spec :-)
msmq: sounds like sub-classing, difference seems to be you're avoiding substitution groups
<scribe> ACTION: pdowney to raise a new issue on 'skip'
<scribe> ACTION: pdowney to raise a new issue on 'lax'
pauld: skip and lax seems to be similar to 'mixed'
jonc: Erik's issue is about defaulting creating a wrapper element
pauld: seems like a common bug which we can document as an issue
<scribe> ACTION: pdowney to investigate xs:default with tools
ISSUE-8 - Using patterns to constrain numerical types
msmq: some patterns may be harmless (ignore leading zeros)
whereas others can be difficult
dezell: patterns could ask for even numbers, multiple of 10
msmq: forbidding some lexical forms as opposed to *all* lexical forms for a value. imagine incrementing a counter then trying to generate a lexical value
- a pattern may prevent or make that task difficult
msmq: procedure is to generate a lexical value, then schema validate it
msmq: Patterns can get complex. Have a schema pattern to only allow modulo any number!
dezell: nice theorem and matches all of my empirical cases
dezell: BASIC seems like don't do it
pauld: wondering how to manage this issue. would like to close it for BASIC and open a separate issue for Advanced
msmq: patterns should be OK for strings, and other lexical forms. Will enumerate (as soon as network wakes up)
... decimal, prescisionDecimal, etc
... strings, URIs and other one-to-one mappings (date times not including minutes and seconds, year, day, etc don't have leading zeros one-to-one mapping) should be OK
... all patterns are ok, so long as they don't remove a canonical form
dezell: boolean?
msmq: if you removed '0' and 'false' then 'true' and '1' would be allowed, checking to see if can serialised would be OK in that case. writing a pattern of '0'|'true' would require an oracle, possible for boolean, but much harder for 'float'.
dezell: '0'|'1' or 'false'|'true' seems to be the common use-case. A pattern could prevent leading zeros, why would that be bad
msmq: a System 370 editor pattern may always lead to a value with a leading zero. A brute-force approach doesn't work for numerical forms, they may be almost infinite.
yves: my pattern allows odd numbers, adding leading zeros will never help ..
dezell: in the advanced we should explain if a pattern eliminates any lexical form, it should eliminate *all* lexical forms of that value. You still have to serialize and then check.
pauld: Sounds like we're moving towards a point where we can craft a concrete proposal.
Lunch!
ISSUE-20 - Extension of collections
Paul introduces topic, cites chartered requirement to consider additonal elements as a use-case
discussion of ignoring additional content.
dezell: extension element, with a model group
pault: ideally you know what types you're going to extend
pauld: the patterns with extension wrapper leads to a staircase of elements
dezell: it's horrible, no matter what you do
pault: sounds like it comes from ASN.1 - cites pattern of extending at the end
dezell: schema 1.1 is looking at extensions at the suffix, or I prefer the validate twice - remove unknowns. turns all type derivation into restriction
pauld: we went down that road with WSDL 2.0 LC124, 'unknown' has to be just that - 'unknown' in the schema
pault: ASN.1 has extensibility implied - adds to the end of each type implicitly
dezell: Schema 1.1 is likely to have good stuff, but not for this WG
discussion of adding to end of structure, contrived extension patterns, v1-v2-v3 evolotions. Sadly detailed notes were lost thanks to pauld's mac crashing and our not being able to use IRC :-(
pault: can't we suggest extension at end in a different namespace
pauld: do you mean identify extension for v2 in v1 structures?
... coming to the conclusion we won't have a basic pattern for versioning, but we'll have to show our working
ISSUE-7 - xsi:nil and minOccurs=0 xsi:nil, Redux
Jonc presents proposed text for ISSUE-7 (projected, not on the list)
pauld: minOccurs=0 and nil=true is a design point
dezell: we discussed this at length, bottom line is nil use-case for database vendors sending missing (unexpected) values (e.g. mirroring databases)
pauld: wants to call out the design point between nil=true and minOccurs=0 as one of our documented issues
... want's to avoid normative advice to toolkit implementers in BASIC patterns
jonc: will continue to work on text and post to list
ISSUE-15 - ASN.1 null datatype
pault: null datatype useful in a choice of types in which one may be explicity missing
... also seen bitstring like applications, for citing missing values
pauld: sounds like yet another semantically different null, minOccurs=0
pault: choice itself could be optional, other ways of making it absent.
... some people wanted to say this explicitly - I always have a value
... it's never sent in packed encodings
pauld: seems like it has use-cases, mapping to ASN.1 is very interesting for fast-XML etc,
but how do current toolkits deal with it? Is it suitable for BASIC patterns?
jonc: worries if this may become an alternative to minOccurs=0 or nillable for empty content
pauld: doesn't seem as attractive as minOccurs or nillable, but has utility for ASN.1
jonc: what happens if you hang attributes off the element?
pault: from ASN.1 perspective, attribute no different to element
pauld: likely to be mapped to a class - my concern is an empty element may not work with tools
... lets park this
<scribe> ACTION: pdowney to investigate null patterns on tools
<scribe> ACTION: pdowney to raise an issue on more than one way to express empty or missing content
General ways forward
pauld: worries about depth of knowledge from within WG, especially wrt practical implementation of schema
pauld: starting to worry less about content, but more about written style of our specs.
yves: specification guidelines from the QA activity will help, may be able to enlist editorial guidance.
<scribe> ACTION: pdowney to plan two Editorial/F2F meetings in Europe
pauld: we need to move forward with the text. noodling on splitting the weekly call to have 15min/45min editorial/WG split
pauld: thanks paulf, and would like to record thanks to our other observers for their valuable input
... and thanks the W3C for hosting!
yves: W3C is sorry about the network!
ADJOURNED!
Summary of Action Items
[NEW] ACTION: pdowney to enumerate schema 'features' for the roadmap
[NEW] ACTION: yves to write a wget script to publish issues on the public page
[NEW] ACTION: pdowney to build list of implementations
[NEW] ACTION: jcalladi to report on code-first experiences with 'all' and toolkits
[NEW] ACTION: yves to craft vector counter example for ISSUE-7
[NEW] ACTION: jcalladi to craft text for ISSUE-7, table followed by 'best practice' against using nil minOccurs=0 and nillable
[NEW] ACTION: msmq to report on status of Schema Collection
[NEW] ACTION: pauld to investigate tools with authoring styles
[NEW] ACTION: pdowney to raise a new issue on 'skip'
[NEW] ACTION: pdowney to raise a new issue on 'lax'
[NEW] ACTION: pdowney to investigate xs:default with tools
[NEW] ACTION: pdowney to investigate null patterns on tools
[NEW] ACTION: pdowney to raise an issue on more than one way to express empty or missing content
[NEW] ACTION: pdowney to plan two Editorial/F2F meetings in Europe
[End of minutes]
Minutes formatted by David Booth's scribe.perl version 1.127 (CVS log)
$Date: 2006/03/12 21:54:41 $
Received on Sunday, 12 March 2006 22:17:59 UTC