A Partial identity (of an entity) is all knowledge that a specific party has about that entity. This entity is referred to as the subject of the partial identity. The party fulfills the role of owner of the partial entity, as the partial identity is part of the knowledge that this party owns (see the party-actor pattern for details).
A party does not control the partial identities of which it is the subject, save 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 author and 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 (which still may or may not be the case).