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Remark: Other feedbacks from the academic federations running categories for a significant time would be enlightening.

The DFN-AAI Experience (DE)

The Identity Federation operated by the German Research and Education Network (DFN) introduced Entity Categories (both for SPs and IdPs) in 2012 in order to support so-called "Virtual Sub-Federations". The setup is based on a whitelist maintained by a specific project or community and which is hooked up with the metadata registry. The project-specific EC is only available for entities listed on such a whitelist - a nightly check removes the EC automatically if an entity disappears from the respective whitelist. Using such an EC, (Shibboleth) SPs are able to select all project-related IdPs from the federation metadata and ignore the rest, while IdPs only have to set up one Attribute Filter Policy in order to release Attributes to a dynamic number of project-related SPs. This concept turned out to be quite popular, meanwhile (2015) three of these ECs are in use, a fourth one has been requested recently.

The CoCo EC was introduced in July 2013, R&S in 2015.  While many SPs registered with the DFN-AAI committed especially to the Code of Conduct, the acceptance by German IdPs is still improvable. One reason for the reluctance of German IdP admins to support the CoCo and R&S ECs is the strictness and complexity of data protection laws and regulations in Germany, cf. http://dariah-aai.daasi.de/attribute-release_and_legal-stuff_wp.pdf

The Greek Federation experience (GR)

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