adding new feature to JAXP validator for folded simpleType->list assertions
evaluation
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Key: XERCESJ-1496
URL: https://issues.apache.org/jira/browse/XERCESJ-1496
Project: Xerces2-J
Issue Type: Improvement
Components: XML Schema 1.1 Structures
Affects Versions: 2.11.0
Reporter: Mukul Gandhi
Assignee: Mukul Gandhi
Priority: Minor
Here' a description of the rationale and benefits of this change, and a small
schema 1.1 validation use case illustrating the proposed changes.
One of the test cases in W3C XML Schema 1.1 test suite is as follows:
XML document [1]:
<list>1 2 3 4 5</list>
XML Schema document [2]:
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema";>
<xs:element name="list">
<xs:simpleType>
<xs:list>
<xs:simpleType>
<xs:restriction base="xs:integer">
<xs:assertion test="count($value) eq
count(distinct-values($value))" />
</xs:restriction>
</xs:simpleType>
</xs:list>
</xs:simpleType>
</xs:element>
</xs:schema>
The assertion facet in this example would mean,
"there must be no duplicates in the list"
Xerces (before this change) didn't support an use case like above. For the
above example Xerces evaluates assertion for each list item (therefore Xerces
would make 5 calls to an assertion for this example, and the XPath 2 context
variable $value being different/"list item" in each iteration) -- but this
would not serve the purpose of this use case.
I believe we must support this use case. To support this facility I propose a
change along the following lines:
Introduce a new feature on JAXP validator with name
"http://apache.org/xml/features/validation/foldedSTlist-assertion-evaluation";
whose default value is an boolean 'false' (therefore not setting this feature
or making it explicitly 'false' would retain the current Xerces behavior).
Setting this feature to 'true' would cause assertion evaluation as required by
the above use case.
The current Xerces implementation to evaluate assertion facet on each list item
is also beneficial; for example with a schema 1.1 fragment something like below:
<xs:element name="list">
<xs:simpleType>
<xs:list>
<xs:simpleType>
<xs:restriction base="xs:integer">
<xs:assertion test="$value mod 2 = 0" />
</xs:restriction>
</xs:simpleType>
</xs:list>
</xs:simpleType>
</xs:element>
(the assertion failure error messages in this example would tell us, that what
all list items didn't pass the test AND I believe that this run-time behavior
is also useful)
To summarize this change:
1. Setting the mentioned JAXP feature to 'true' would cause assertion to be
evaluated only once on the entire list (which would have a type annotation
xs:anyAtomicType*).
2. Not setting this JAXP feature explicitly (since it's default value is
'false' within Xerces XML Schema 1.1 validator), or setting explicitly it's
value to 'false' would retain the current Xerces behavior as has been explained
above.
I hope that this enhancement is useful. I'll shortly be committing changes for
this facility (along with related support in jaxp.SourceValidator sample). Any
comments about this change would be helpful to us.
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