There is a misleading description of identity-realm in DMR [1]. It says "A security realm definition where identities are represented in the management model." whereas an XSD documentation says "Realm definition for a realm which contains a single pre-defined identity.".
In general, the XSD description looks clearer to me. Moreover, the identities word may be misleading since identity-realm's purpose is to "to store one identity, with one attribute and no credential" [3]. Thus I would suggest to also change the description of attribute-values from
"The values associated with the identities attribute." to something like "The values associated with the identity attributes."

Suggestions for improvement:

• Change description identity-realm according to XSD
• Change description of attribute-values attr (in both DMR and XSD)
• to consider: unify descriptions in XSD and DMR

[1] /subsystem=elytron/identity-realm=somerealm:read-resource-description
[2] https://github.com/wildfly-security/elytron-subsystem/blob/master/src/main/resources/schema/wildfly-elytron_1_0.xsd#L412
[3] HipChats's WildFly Elytron chat room on Nov 21