AW: AW: [sdo] Update of remaining XML Fidelity duplicate names issues

["Barack, Ron" <ron.barack@sap.com>]

Hi Frank, others,

I think we should try a little harder, here.  SAP is part of the camp that does not think of SDOPath's similarity to Xpath as being required for XML fidelity, but we do see the need to to have a SDOPath with a readable, understandable syntax, that can address any property.  I think SDO will be weakened if we don't offer some standard solution here.  We at SAP can live with Oracle's as well as IBM's proposals, maybe we will have luck and be able to find a middle ground.

One reason why I think the "xml:" notation is superior to IBM's proposal is that it allows implementations more flexibility in deciding how to handle conflicting local names, that is, it allows implementations to mangle the SDOName.  Or not.  The XML name, qualified by "@" or by "namespace-uri" seems to be our only chance of coming up with a standard way to name the property for the purposes of SDOPath.

But while allowing for name mangling, Oracle's proposal (I mean here proposal 1) does not require it.  As I understand the current proposal, however, the "xml:" prefix is not really othogonal to the "namespace-uri" predicates, namely, the "namespace-uri" can only in association with "xml:".

One thing we could do is weaken this, allow namespace-uri to be used with or without the "xml" prefix.  First of all, we need to weaken it anyway, to handle open content properties, So why not just say the two predicates are orthogonal.  One way to look at an SDOPath element is that it's a query on the metadata.  Saying o.get("x") essentially performs a query on the instance properties, returning the property where p.getName().equals("x").  Saying o.get("x[namespace-uri()='foo']") is simply adding another clause to the query, asking that additionally XSDHelper.getNamespaceURI(p).equals("foo").

If we go in this way, then at least we give the implementation the choice not to do any name mangling, and for such implementations, since the SDO name will be the same as the XML name, the "xml:" prefix becomes optional, so the SDOPath string becomes exactly what Frank suggested in his proposal.  True, this will be implementation specific behavior, as will any behavior that relies on the implementation's name mangling algorithm.  But at least we have a standard, portable solutions that allows the vendor specific solution that IBM would prefer.  

We could also go to the other extreme and say that namespace-uri implies the use of an XML name, that is, that "xml:" is redundant in this case.  Then we also get SDOPaths that look like Xpath, but we loose the ability to use the SDO name with namespace-uri.  I also think it's a bit convoluted for one clause in the "metadata query" to affect the meaning of the other clause.

Regarding the "@" operator... It's true that using it to distinguish attributes and elements is a breaking change.  It would, however, be a breaking change that is in SAP's opinion fully acceptable:  we don't think may users are relying on this behavior, we don't think there will be many breaks.  Blaise's arguement that the character sets us up for further extensions of other datacentric languages is something I haven't really been able to understand.  Perhaps, Blaise, you could describe what such a possible future extension might be.  Otherwise, I would rather try to get a consensus solution to the current issues.


Ron

-----Ursprüngliche Nachricht-----
Von: Frank Budinsky [mailto:frankb@ca.ibm.com] 
Gesendet: Freitag, 5. September 2008 03:29
An: sdo@lists.oasis-open.org
Betreff: Re: AW: [sdo] Update of remaining XML Fidelity duplicate names issues

Hi guys,

I've spent quite a bit of time thinking about and discussing the attached 
proposal within IBM, but unfortunately the conclusion is that we don't 
find it to be an acceptable solution for these issues. By this, I mean the 
SDOPath part of the proposal (option 1 or 2). As we agreed (and voted) in 
last week's TC call, we do like and support the XSDHelper.getProperty() 
part of the proposal.

The problem with the SDOPath part of the proposal is that it doesn't meet 
our (IBMs) goal of XPath Fidelity. IBM feels that XPath Fidelity is an 
important part of XML Fidelity in general. That is, SDOPaths should be as 
compatible with XPath as possible and thus as natural as possible for an 
XML-savvy programmer to use. Neither using xml: prefixes in the path nor 
using (verbose) function syntax meets this requirement. We also don't see 
a use case that would require the ability to mix SDO name matching and XML 
name matching within the steps of a single path, so the additional 
complexity is not warranted in our view.

Given that it appears that others don't feel as strongly about XPath 
Fidelity, and since we need to start making more progress given our target 
date for SDO 3, we feel it would be best to end the discussion of these 
issues and simply leave the spec as it is, only making sure that 
implementations are allowed to solve these issues in 
implementation-dependent ways. Although we realize that this is less 
satisfying than to agree on a standard solution, we feel that the 
XSDHelper.getProperty() method that we've agreed to already provides one 
way to handle duplicate names. We believe that also handling them though 
SDOPath via an implementation-dependent approach will be good enough.

I believe that the IBM solutions to these issues (described below) are 
arguably compliant with the spec already. This conclusion is based on one 
of my favorite paragraphs in the spec :-) That is, section 3.1.3: 

SDO specifies minimum functionality for implementations. An implementation 
may provide additional function so that valid results would be returned 
where this specification would produce an error, provided that the 
functionality is a strict superset and all valid uses of the SDO 
specification operate correctly. 

Also, this wording in section 12: 

names including any of the special characters of the syntax (./[]='"@) are 
not accessible.

I interpret section 12 to mean get("@foo") would be an error condition. 
However, according to 3.1.13 an implementation can "provide additional 
function" in this case. IBM, for SDO-71 (for example), would go the route 
of providing the additional function of adding "@foo" as an aliasName for 
attribute backed properties named "foo" and then allowing them to be 
accessed through DataObject.get("@foo"). 

Does anybody believe that we are wrong in this assumption, in that this 
would make IBM's implementation of SDO noncompliant? The only possible 
issue I can see is this sentence in section 12: 

The presence or absence of the @ sign in a path has no meaning. 

This seems to imply that implementations MUST implement get("@foo") to 
return an element-backed property, if it is the first foo in the list. In 
my opinion, a user would likely consider this an error. It conflicts with 
the purpose of allowing the @ sign in the first place (to allow standard 
XPath syntax to be used to retrieve attribute-backed property values).

Although, maybe IBM could argue that our implementation provides 
"additional function" in this case as well - i.e., in our implementation 
the presence or absence of the @ sign in a path HAS meaning.

Does anybody believe that the SDO spec should say that an implementation 
is noncompliant if it doesn't return an element from get("@foo"), when the 
first foo property is an element? I think that, as we've always tried to 
do in the past, it would be in SDO's best interest to remove this (or any 
other) wording that appears in the spec which is necessary in order to 
allow this to be compliant (i.e., allow an implementation to do better).

Thanks,
Frank




Blaise Doughan <blaise.doughan@oracle.com> 
08/26/2008 09:44 AM

To
sdo@lists.oasis-open.org
cc

Subject
Re: AW: [sdo] Update of remaining XML Fidelity duplicate names issues






Hello All,

Attached is the Oracle proposal addressing the following SDO issues:
SDO-67 Handling of Namespace in SDO Path (section 2.1.4)
SDO-71 SDOPath handling of '@' character (section 2.1.1)
SDO-83 Clarification of special "value" property and how to avoid name 
clashes (section 2.1.5)
-Blaise

Frank Budinsky wrote: 
Hi guys,

The current status of at least SDO-67 is that we're waiting to evaluate a 
counter proposal from Oracle. I'm not sure if it will also address SDO-71 
(or SDO-83, which the current SDO-71 proposal also solves). If so, we need 

to see this proposal and evaluate it ASAP. Otherwise, I'd like to suggest 
making SDO-71 an optional feature. All that's needed for that is to 
"allow" SDO names to include the '@' character after which IBM, or anyone 
else that wants to, could implement SDO-71 as described below, and still 
be spec compliant.

The final issue below, SDO-82, is unrelated. Are there any objections to 
that proposal? If not, can we at least resolve it?

It looks like our tentative plan to publish a CD by the end of August is 
becoming highly unlikely. I think we need to put a greater sense of 
urgency on making progress on this spec, or I feel that SDO 3 may come 
unravelled.

Comments?

Thanks,
Frank




"Barack, Ron" <ron.barack@sap.com> 
08/11/2008 06:32 AM

To
Frank Budinsky/Toronto/IBM@IBMCA, <sdo@lists.oasis-open.org>
cc

Subject
AW: [sdo] Update of remaining XML Fidelity duplicate names issues






Hi Frank

I like these proposals.  Two comments, additions.

First, I would like to go through the document and take out all text 
stating that name conflicts must be resolved by annotating with sdo:name. 
We are now allowing duplicate SDO names, and specifying the behavior.

Second, when dealing with name conflicts, I would rather avoid explicitly 
requiring name mangling.  I would rather say that the e.g., attribute 
names must never hide element names.  This is the behavior that is 
interesting for the user.  Name mangling is an implementation detail in 
order to achieve this.  Your wording for proposal 3 is actually already 
what I have in mind, and I would like similar wording in proposal 2.


Ron

-----Ursprüngliche Nachricht-----
Von: Frank Budinsky [mailto:frankb@ca.ibm.com] 
Gesendet: Freitag, 8. August 2008 22:02
An: sdo@lists.oasis-open.org
Betreff: [sdo] Update of remaining XML Fidelity duplicate names issues

Hi Guys,

I've updated the 4 remaining unresolved duplicate name proposals, to 
reflect the discussions/feedback so far.

The remaining issues are (see also section 2.1 in 
http://www.oasis-open.org/committees/download.php/26722/SDO_XML_Issues.doc
):

1. SDO-67 Handling of Namespace in SDO Path (section 2.1.4)
2. SDO-71 SDOPath handling of '@' character (section 2.1.1)
3. SDO-82 Name conflicts with anonymous XSD types (section 2.1.2)
4. SDO-83 Clarification of special "value" property and how to avoid name 
clashes (section 2.1.5)

I'd like to further discuss and hopefully vote on these proposals during 
next weeks TC call.

Thanks,
Frank


PROPOSAL 1. SDO-67 Handling of Namespace in SDO Path (section 2.1.4)

The resolution to this issue is to extend the SDO Path syntax to support 
the namespace-uri() function from standard XPath. Although the syntax is 
somewhat ugly, it's important to not invent our own syntax, but instead 
conform to the original goal of SDOPath which was to be (mostly) a 
compatible subset of proper XPath. 

Given the following schema:

    <xsd:complexType name="TwoBars">
        <xsd:sequence>
            <xsd:element name="bar" type="xsd:string"/>
            <xsd:element ref="tns2:bar"/>
        </xsd:sequence>
    </xsd:complexType>

An SDO user can then retrieve the second "bar" property as follows:

dataObject.get("bar[namespace-uri()='http://the-tns2-namespace']");

As in previous versions of SDO:

dataObject.get("bar");

would continue to return the first "bar".

The specific change to the SDO 2.1 spec is in section 12, change:

step ::= '@'? property
      | property '[' index_from_1 ']'
      | property '.' index_from_0
      | reference '[' attribute '=' value ']'
      | ".."

to the following:

step ::= '@'? property
      | property '[' index_from_1 ']'
      | property '.' index_from_0
      | property '[' namespace-uri() '=' uri ']'
      | reference '[' attribute '=' value ']'
      | ".."

uri ::= '"' anyURI "'" 
      | "'" anyURI "'"


In addition to the above resolution, Stefan has proposed adding the 
following methods to XSDHelper:

XSDHelper.getProperty(Type type, String uri, String xsdName, boolean 
isElement)
XSDHelper.getInstanceProperty(DataObject, String uri, String xsdName, 
boolean isElement)

These methods provide a non-SDOPath alternative for handling this issue as 


well as SDO-71. I'm also OK with adding these methods.


PROPOSAL 2. SDO-71 SDOPath handling of '@' character (section 2.1.1)

TestCase in ZIP file: DuplicateNamesTest.testAttributeElementClash()

The resolution to this issue is to require implementations to 
automatically mangle the name of attributes that conflict with an element 
in a type, and to also specify that XSD attributes will map to properties 
that have @name as an aliasName.

Given the following schema:

    <xsd:complexType name="TwoFoos">
        <xsd:sequence>
            <xsd:element name="foo" type="xsd:string"/>
        </xsd:sequence>
        <xsd:attribute name="foo" type="xsd:int"/>
    </xsd:complexType>

This will produce an SDO Type named "TwoFoos" with two properties:

1. name="foo", type=String
2. name="some_mangled_name", type=Int, aliasName="@foo"

An SDO user can then retrieve the foo element as follows:

dataObject.get("foo");

And the foo attribute like this:

dataObject.get("@foo");

Although this solution is not 100% backwards compatible (i.e., it does not 


allow an XML element to be accessed using the "@name" syntax), it is 
backwards compatible for all practical purposes, since it's highly 
unlikely that there are any existing SDO users that rely on the ability to 


use the @ syntax to retrieve element properties.

Note 1: with this proposal, an attribute-backed property that appears 
after an element-backed property in the getProperties() list does not 
necessarily conflict, since the spec already says that in the case of 
duplicates the first property will hide the others. Since the goal of this 


resolution is to ensure that the element-backed property will always take 
precedence we could allow an implementation to choose not to actually 
mangle the attribute-backed property name in this case, as long as it 
still sets the aliasName as specified above.

Note 2: with this solution SDO Path works with SDO names. The 
attribute/element aspects only impact the mapping from XSD to SDO. 

The specific changes to the SDO 2.1 spec for this issue are:

1) In section 9.3 change:

If elements and attributes within a complexType, and its base types, have 
the same local name then unique names must be assigned by sdo:name. 

to the following:

If elements and attributes within a complexType, and its base types, have 
the same local name and unique names are not assigned by sdo:name, then an 


implementation will automatically rename the attribute property (i.e., the 


one for which XSDHelper.isAttribute returns true) to an 
implementation-dependent mangled name. 

(NOTE, do we want to open another issue to consider standardizing the 
mangled name used for conflicting attributes? Personally, I think that if 
users care, they should use sdo:name annotations.)

2) In section 9.3.1, first row of the table (i.e., "Attribute" row), 
change:

Property name=[NAME] 
  type=[TYPE]

to the following:

Property name=[NAME] 
  type=[TYPE]
  aliasName=@[NAME]

3) In section 12, change:

step ::= '@'? property
      | property '[' index_from_1 ']'
      | property '.' index_from_0
      | reference '[' attribute '=' value ']'
      | ".."
property ::= NCName      ;; may be simple or complex type
attribute ::= NCName     ;; must be simple type
reference :: NCName      ;; must be DataObject type

to the following:

step ::= property
      | property '[' index_from_1 ']'
      | property '.' index_from_0
      | reference '[' attribute '=' value ']'
      | ".."
property ::= sdoName      ;; may be simple or complex type
attribute ::= sdoName     ;; must be simple type
reference ::= sdoName      ;; must be DataObject type
sdoName ::= '@'? NCName

Also in section 12, change:

The presence or absence of the @ sign in a path has no meaning. Properties 


are always matched by name independent of their XML representation.

to the following:

Unlike standard XPath, the @ sign is not required for accessing 
attribute-backed properties. It can be used to access properties that have 


an aliasName that includes the @ sign, typically XML attributes - see 
section 9.3.1.


PROPOSAL 3. SDO-82 Name conflicts with anonymous XSD types (section 2.1.2)

TestCase in ZIP file: DuplicateNamesTest.testAnonymousTypeClash()

This issues has already been partially resolved in SDO 2.1.1 (JSR 235). In 


JSR 235 it was agreed that anonymous types in locally defined elements are 


automatically mangled so as not to conflict with global types. For 
example:

    <xsd:complexType name="personRoot">
        <xsd:sequence>
            <xsd:element name="person">
                <xsd:complexType>
                    <xsd:sequence>
                        <xsd:element name="identifier" type="xsd:string"/>
                    </xsd:sequence>
                </xsd:complexType>
            </xsd:element>
        </xsd:sequence>
    </xsd:complexType> 

Unlike SDO 2.1, in SDO 2.1.1 the anonymous type declared under the local 
"person" element will not conflict with a global type "person" such as:

    <xsd:complexType name="person">
        <xsd:sequence>
          <xsd:element name="firstName" type="xsd:string"/>
          <xsd:element name="lastName" type="xsd:string"/>
        </xsd:sequence>
    </xsd:complexType>

However, in JSR 235 it was not required that an implementation also mangle 


the name of an anonymous type under a global element:

    <xsd:element name="person">
        <xsd:complexType>
            <xsd:sequence>
                <xsd:element name="name" type="xsd:string"/>
            </xsd:sequence>
        </xsd:complexType>
    </xsd:element>

The proposed resolution to this issue is to take the extra step to say 
that the name of this anonymous type must also be mangled. This is 
required in order for SDO to guarantee that:

typeHelper.getType(NS_DUPLICATES, "person");

will always return a real globally defined complexType, as above.

The specific change to the SDO spec for this issue is:

1) the changes to reflect the resolution of the issue in JSR 235
2) State clearly that anonymous types (under local or global 
elements/attributes) will never be given name that hides a globally 
defined type with the same name.


PROPOSAL 4. SDO-83 Clarification of special "value" property and how to 
avoid name clashes (section 2.1.5)

TestCase in ZIP file: DuplicateNamesTest.testValuePropertyClash()

Since only attributes named "value" can conflict with the special "value" 
property, the solution to Proposal 2 (SDO-71) will also solve this issue, 
as long as the special "value" property is treated like an element-type 
property. This will be the case, given the proposed wording for SDO-71, 
that is, it uses XSDHelper.isAttribute() as its test. Therefore, since the 


special "value" property is not an attribute, it will be treated like an 
element.



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