Note that because a partial identity is knowledge of that party, it follows automatically that this party is also the owner of that partial identity.
A party does not control the partial identities for which it is the subject, except the one that it owns itself (its self-concept). People that expect they can own all partial identities of which they are the subject, are in for disappointment, as all (except one) such partial identities are outside their scope of control.
Parties that issue credentials about an entity thus issue claims that are part of the partial identity that this party has about the entity. If that party is coherent and consistent in its knowledge, and does not lie, then we may assume that the set of claims in the credential of an issuer is also coherent and consistent, and that this party believes that the knowledge represented by such claims is true.