OK found this. I am not completely clear as to the change to be made to the
schema or to core however.
I assume that this means that
1) no change to the spec is required
2) only change to core is the addition of a note to explain the useage
I have added the following explanatory note in AttributeValue:
If the data content of an AttributeValue element is of a XML Schema simple
type (e.g. interger, string, etc) the data type MAY be declared explicitly
by means of an xsi:type declaration in the <AttributeValue> element. If the
attribute value contains structured data the necessary data elements may be
defined in an extension schema introduced by means of the xmlns= mechanism.
This is not completely clear, but the only way to make it clearer would be
to introduce some examples, which hitherto we have not done in the core
document.
I suggest we revisit this in the committee last call.
Phill
Phillip Hallam-Baker FBCS C.Eng.
Principal Scientist
VeriSign Inc.
781 245 6996 x227
> -----Original Message-----
> From: Chris McLaren [mailto:]
> Sent: Tuesday, December 04, 2001 2:11 PM
> To: 'oasis sstc'
> Subject: [security-services] A15 & A23: Attribute Values
>
>
> A number of suggestions have been made and questions raised
> with regards to
> the use of the <saml:Attribute> element, specifically around how to
> communicate the "type" of the contents of the
> <AttributeValue> element. I'm
> going to attempt to answer what I think some of those questions are.
>
> 1. How is someone supposed to know what to do with the
> <AttributeValue>
>
> First, simple, answer: Every <Attribute> has an "AttributeNamespace"
> attribute that functions as a context identifier for what's
> in the element's
> <AttributeValue>. This "AttributeNamespace" could identify a
> publiclly-available DTD or schema, or could refer to something more
> proprietary. Essentially this can be used as the key that tells a SAML
> consumer how to interpret the <AttributeValue>. Note that there is no
> requirement that the combination of the AttributeName and
> AttributeNamespace
> attributes uniquely identify a type for the data contained in the
> value--they MAY, but they are not required to.
>
> For a more generic form of this solution it is noted that
> there are some XML
> specifications that allow generic serialization of objects
> into XML, and the
> AttributeNamespace can be used to identify these specifications.
>
> Second, better, answer: The <AttributeValue> element can have
> an "xsi:type"
> attribute added to it that indentifes the type of the contents.
> <AttributeValue> contains an "any" element, which in the
> schema definition
> is assigned the type "xsd:anyType". Since "xsd:anyType" is
> the ur-type from
> which everything in schema is derived, any other schema type
> counts as a
> descendant type, and can thus be used in xsi:type substitution.
>
> In other words, it is perfectly valid to have an Attribute
> that looks like
> this:
>
> <Attribute AttributeName="my_name"
> AttributeNamespace="some_namespace">
> <AttributeValue xsi:type="prefix:SomeType">
> ... contents as defined by the prefix:SomeType
> definition in the prefix
> schema
> </AttributeValue>
> </Attribute>
>
> This amounts to using definitions from another schema to
> define the contents
> of your values.
>
> 2. What if all my values are just simple types like strings
> and integers?
> Why should I have to pull in another schema for
> <AttributeValue> for these
> simple cases?
>
> You don't have to. You already have "pulled in" the
> definitions from schema
> itself (and probably schema-instance also). You can use these
> exactly as in
> the second answer above. You just use type substitution to
> specify what type
> your value is, and point to the simple types defined in
> schema itself. For
> example:
>
> <Attribute AttributeName="Department"
> AttributeNamespace="some_namespace">
> <AttributeValue xsi:type="xsd:string">
> Engineering
> </AttributeValue>
> </Attribute>
>
> 3. Why isn't this stuff in the core document?
>
> Does it really belong there? Perhaps a line of the form "If
> your attribute
> values are simple types defined in XML Schema you SHOULD add xsi:type
> attributes to the <AttributeValue> element identifying their
> type." with an
> example could be added to the <AttributeValue> section, with
> a link to a
> more complete discussion in non-normative text somewhere?
>
> --
> Chris McLaren, Principal Engineer
> B2B Research Group Netegrity, Inc.
>
>
>
>
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