Hi Everyone,
Based on yesterday’s discussion, let me offer an example as a basis for discussion. For clarity, I’m leaving out all namespace stuff
We start with a schema that defines a simple type:
<xs:simpleType name=”MySimpleType” base=”xs:integer”>
<xs:minInclusive value=”5”/>
</xs:simpleType>
Let’s assume the schema defining this type is read in and that SDO has created the type. Sometime later, we read in another schema that uses the type in an element property… I’m imagining it in a second schema, if the use is in the
same schema, we could potentially decide when defining the type that it’s instance class should be Integer and not “int”, but if the usage is in a second schema, then clearly we can no longer modify the existing type definition. So, let’s imagine a second
schema
<xs:element name=”MyDoc” type=”MyComplexType”>
<xs:complexType name=”MyComplexType”>
<xs:sequence>
<xs:element name=”mst” type=”MySimpleType”/>
<xs:element name=”mst_nillable” xs:nillable=”true” type=”MySimpleType”/>
<xs:element name=”i” type=”xs:integer”/>
<xs:element name=”i_nillable” xs:nillable=”true” type=”xs:integer”/>
</xs:sequence>
</xs:complexType>
Here’s an instance document:
<MyDoc>
<mst>7</mst>
<mst_nillable xsi:nil=”true”/>
<i>21</i>
<i_nillable xsi:nil=”true”/>
</MyDoc>
Let’s imagine some code using these files:
DataObject myObject = xmlHelper.load(…).getRootObject();
Type complexType = myObject.getType();
Property pMst = complexType.getProperty(“mst”);
Property pMstNillable = complexType.getProperty(“mst_nillable”);
Property pI = complexType.getProperty(“i”);
Property pINillable = complexType.getProperty(“i_nillable”);
So, I guess the first question is:
Q1: What is the value of pMstNillable.getType()?
A1-1: pMst.getType(), that is pMstNillable.getType().getName().equals(“MySimpleType”);
I think this is what users would expect.
A1-2: sdo:IntObject, that is pINillable.getType().
This is what the spec currently says. But of course, we are losing information…in this case, the restriction. Not to mention that theres a round-tripping problem.
I guess A1-1 is preferable, but it creates problems when dealing with nils. This brings us to our second question:
Q2: Assuming “A1-1”, what should myObject.get(pMstNillable) return?
A2-1: 0 – this would mean ignoring the nillable attribute.
A2-2: null – this gives the detail about nil value, but I think users will still be surprised, since the value is inconsistent with the property’s metadata.
A2-3: A wrapper data object, and we could add some means of inspecting it for “isNull”… this is the pattern we use when dealing with dataTypes that need to be handled like objects.
Q2: Assuming “A1-1”, what should myObject.get(Integer.class, pMstNillable) return?
A2-1: Integer.valueOf(0) – this would mean ignoring the nillable attribute.
A2-2: null – this is what users would expect. It would mean the implementation must remember the xsi:nill=”true” in addition to the integer value.
BTW, sorry if there are errors in the schema or java code…this is only meant to be the basis for discussion, and I think the intent is clear.
My own current thinking is that the first answers to each question is the best choice. But maybe there are other solutions.
OK… let the discussion begin!
Ron
_____________________________________________
Von: Barack, Ron
Gesendet: Dienstag, 17. August 2010 16:31
An: sdo@lists.oasis-open.org
Betreff: ISSUE 99: Error in allocating SDO Type for elements with nillable=true
Hi everyone.
In the current WD, the problem is in the table in section 7.4.2, in the block “Element with nillable”. There are a lot of editorial issues with this text, for instance, the reference to Java types does not really belong
in the core spec. but more substantively: the issue boils down to the problem that “xsi:nillable” is on properties, but “sdo:nullable” is on types. If you have a type that is defined as being an unboxed primitive value, we can’t simply change the type’s
definition because it’s used in a nillable property. (I hope we all agree here).
In my opinion there are 4 possibilities.
- We ignore the xsi:nillable
- We use a SDO primitive object type (IntObject), and use the type referenced in the XSD as the XmlType only.
- We use wrapper objects.
- We defer the issue
I prefer option 3 and volunteer to write it up, if we get approval for the approach on today’s call.
Ron