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Service Providers should only request attributes that the service actually uses, so for example if email address is not required by the service it should not be requested. The specification does not explicitly prevent Service Providers from requesting attributes outside the R&S attribute bundle but the expectation is strongly suggests that they should notdo not ("Service Providers SHOULD request a subset of R&S Category Attributes", section 5 of the specification). R&S works best for both Identity Providers and Service Providers when the bundle is treated as the maximal set of attributes requested. Service Providers requiring more unique / bespoke attribute bundles should talk to the REFEDS community.
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