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Specification documenting the binding obligations on UMA participants. (You can see the old document that used to live on this page by visiting old revisions.)
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http://kantarainitiative.org/confluence/display/uma/UMA+Trust+Model+User+guide
Domenico Catalano's latest work on leveraging UMA in an actual deployed ecosystem.
http://kantarainitiative.org/confluence/display/uma/Measuring+elements+of+Trust
Domenico's early study analyzing the UMA trust proposition.
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