An entity attribute is a SAML attribute associated with a SAML entity (an identity provider or a service provider) in metadata. For example, an entity ID is a distinguished entity attribute associated with every SAML entity in metadata.
...
In this case, the name of the attribute is http://macedir.org/entity-category and its value is http://id.incommon.org/category/research-and-scholarship. Like all SAML attributes, an entity attribute may be single-valued or multi-valued. (As it turns out, the above entity attribute is multi-valued.)
Uses
Entity attributes turn out to be are extremely useful. Operationally, entity attributes are used in policy configurations in lieu of entity IDs. The advantages of doing so are overwhelmingly positive.
...