Thank you, Valerio and Joni, for the clarification. I now understand what you are trying to achieve with the ordering of VO membership attributes. Instead of relying on the ordering of attributes, which implicitly conveys a primary attribute, even in those cases where a primary does not exist, why not make the primary attribute explicit? As an example, consider the eduPerson specification http://www.nmi-edit.org/eduPerson/internet2-mace-dir-eduperson-200604.html on which the MACE-Dir SAML Attribute Profiles is based http://middleware.internet2.edu/dir/docs/internet2-mace-dir-saml-attributes-... There we have a multi-valued attribute called eduPersonAffiliation and a corresponding single-valued attribute called eduPersonPrimaryAffiliation. The ordering of attribute values within eduPersonAffiliation is unspecified while eduPersonPrimaryAffiliation exposes a distinguished such attribute value. Making the primary affiliation explicit is preferable to an implicit ordering, I think. Can VO membership be handled in this way? Cheers, Tom On 10/31/06, Joni Hahkala <joni.hahkala@cern.ch> wrote:
Just extending a bit with the reasoning we have used in EGEE...
Yes, the "primary" VO and group etc are important for the accounting, for example who gets changed for the CPU time and the storage space. Also usually it is good to have a concept of file owner, which the primary group/vo facilitates.
For the plain access control they are probably not so important, unless you think the obligations like account name etc are part of access control.
Cheers, Joni
Valerio Venturi wrote, On 10/31/2006 03:21 PM:
On 10/16/06, Valerio Venturi <valerio.venturi@cnaf.infn.it> wrote:
Attribute Authority Interface We've red the OASIS draft that we were pointed to in Washington OGF by Tom Scavo and found it good and detailed. It's pretty much like what we were thinking about, so we dont' think there's need for producing another doc which won't add much. We'll contact Tom with some concerns we have. We look forward to your feedback regarding this draft document.
VOMS first attribute Frank Siebenlist asked whether it would be possible to add a tag to mark the first of VOMS attributes (both in the context of Attribute Certificates and SAML Assertions) since it had a special semantic. Actually, it is the order of the attributes that is meaningfull in VOMS, not only the first. The voms client indeed have a mean of specyfing the entire order in which attributes appear. In the context of AC, this is not a problem since you can specify order in a ASN.1 SEQUENCE. It is in the context of a SAML Assertion, since despite the fact that most of the parser will return the child elements of AttributeStatement as they appear in the doc, this is not mandatoiry. So we are thinking about how to retain the same behaviour using SAML Assertion. The ordering of Attribute elements in a SAML AttributeStatement is unspecified. If an ordering is required, a new XML indexing attribute is needed: index="1", index="2", etc. Can you explain why such an ordering is required (or just point me to the relevant document where this is discussed)? Sorry for the late reply Tom. Probably we won't need ordering of Attributes, since we'll change the rendering of VOMS attributes using SAML. (we will move the problem to AttributeValue ordering, and we'll probably be doing what you suggested). However, in general, ordering of VOMS attributes is needed because it is relevant to authorization decisions. VOMS may return a
On Mon, 2006-10-16 at 13:25 -0400, Tom Scavo wrote: list of groups in the VO that the user belong to and an authorization function may want to know which groups are more relevant (if some are). As a real life example, mapping to local accounts in gLite grid is done after the first group present in the VOMS AC.
Valerio
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