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RE: [xacml] [CR] DataType attribute required?

  • 1.  RE: [xacml] [CR] DataType attribute required?

    Posted 08-29-2002 16:00
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    Subject: RE: [xacml] [CR] DataType attribute required?


    On Thu, 29 Aug 2002, Daniel Engovatov wrote:
    
    >
    > ..which raises another issue.
    >
    > Do we want to allow the same named attribute to be declared of
    > different types in different rules.
    >
    > So that "AccountNumber" is used as integer in one rule, and as <date> in
    > another..
    >
    > Having "DataType" specified, we may specify that within one PolicySet,
    > same AttributeId should be associated with one and only one data
    > type..
    
    Still, you can infer the type information from the functions applied in
    the expression it appears in.
    
    -Polar
    
    
    >
    > Daniel.
    >
    >
    > -----Original Message-----
    > From: Polar Humenn [mailto:polar@syr.edu]
    > Sent: Thursday, August 29, 2002 12:29 PM
    > To: XACML
    > Subject: RE: [xacml] [CR] DataType attribute required?
    >
    >
    >
    > Such is the thingy with "optional" attributes. If we don't need them now,
    > why have them. You can always "add" an optional attribute to the schema
    > later, unless there is some non-standard use for it. Otherwise if it
    > exists, it just holds redundant information.
    >
    > -Polar
    >
    > On Thu, 29 Aug 2002, Daniel Engovatov wrote:
    >
    > >
    > > That is correct.
    > >
    > > When we started discussion about functions, at least my personal idea was
    > > that
    > > if you specify data type within arguments - you can overload function
    > > names (so when you see add(integer, integer) you know which add to use).
    > > But then we decided to have argument type embedded into function names, so
    > > now we have all string-sequence and decimal-member-of.  Type of the
    > argument
    > > is indeed redundant now - as the external source is not aware of XACML
    > types
    > > and
    > > PDP gets everything encoded as strings anyway..
    > >
    > > But this will work as long as we do not allow any type conversions ever.
    > If
    > > we
    > > decide to specify that any functions taking a decimal (numeric) can also
    > > take
    > > an integer, and promote it to decimal, you may get yourself an ambiguous
    > > situation
    > > with extensions.
    > >
    > > If I remember correctly - that was exactly the reason  - at some point we
    > > have
    > > proposed implicit promotion between numeric datatypes..
    > >
    > > I think no much harm is done by having DataType embedded.
    > > Simplifies some things..  May be more useful in the future..
    > >
    > > Daniel.
    > >
    > >
    > >
    > >
    > > -----Original Message-----
    > > From: Polar Humenn [mailto:polar@syr.edu]
    > > Sent: Thursday, August 29, 2002 11:42 AM
    > > To: Michiharu Kudoh
    > > Cc: xacml@lists.oasis-open.org
    > > Subject: Re: [xacml] [CR] DataType attribute required?
    > >
    > >
    > >
    > > Taking this approach to the extreme, means you really need a typechecking
    > > compiler that not only "checks" the type correctness of the policy, but to
    > > WILL HAVE TO "infer" the types of the elements, which is a little bit of a
    > > harder problem. However, in this simple type system (i.e. no recursive,
    > > abstract types), it's not much harder.
    > >
    > > So, if you go that far, you might as well eliminate DataType attribute
    > > altogether from the schema, as it doesn't buy you anything but possible
    > > confusion.
    > >
    > > As as Michiharu says "In most cases...". However, I would say "In all
    > > cases...." since we can see every expression only appears in a Target or
    > > Condition. The top level expressions in a Target or a Condition in XACML
    > > must result in xs:boolean, and as Michiharu states, the types of all
    > > elements in the expression can be "inferred" from the functions applied to
    > > them.
    > >
    > > I would propose to remove the DataType attribute, in this case.
    > >
    > > Cheers,
    > > -Polar
    > >
    > > On Thu, 29 Aug 2002, Michiharu Kudoh wrote:
    > >
    > > > DataType attribute in AttributeDesignatorType is 'required'. But in most
    > > > cases, AttributeDesignator is used below the matching function (e.g.
    > > > string-match) and that function is type-specific. So I think "DataType"
    > > > attribute is not required. I propose to change it to "optional".
    > > >
    > > > <xs:complexType name="AttributeDesignatorType">
    > > >   <xs:attribute name="AttributeId" type="xs:anyURI" use="required"/>
    > > >   <xs:attribute name="DataType" type="xs:anyURI" use="required"/>
    > > >   <xs:attribute name="Issuer" type="xs:anyURI" use="optional"/>
    > > > </xs:complexType>
    > > >
    > > > [should be]
    > > > <xs:complexType name="AttributeDesignatorType">
    > > >   <xs:attribute name="AttributeId" type="xs:anyURI" use="required"/>
    > > >   <xs:attribute name="DataType" type="xs:anyURI" use="optional"/>
    > > >   <xs:attribute name="Issuer" type="xs:anyURI" use="optional"/>
    > > > </xs:complexType>
    > > >
    > > > Michiharu
    > > >
    > > > IBM Tokyo Research Laboratory, Internet Technology
    > > > Tel. +81 (46) 215-4642   Fax +81 (46) 273-7428
    > > >
    > > >
    > > >
    > > >
    > > >
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