anchor.diff:  (define-resource musician-group ()
     :class (s-prefix "bravoer:MusicianGroup")
     :properties `((:name :string,(s-prefix "vcard:hasName"))
  -		(:created :date ,(s-prefix "dcterms:created"))
  -		(:modified :date ,(s-prefix "dcterms:modified")))
  +		(:created :datetime ,(s-prefix "dcterms:created"))
  +		(:modified :datetime ,(s-prefix "dcterms:modified")))
     :resource-base (s-url "http://data.bravoer.be/id/musician-groups/")
     :has-many `((musician :via ,(s-prefix "vcard:hasMember")
   			:as "members"))
  
positive.code: 		(:organization-name :string ,(s-prefix "vcard:hasOrganizationName"))
                  (:communication :string ,(s-prefix "bravoer:communicationsMedium"))
  		(:email :url ,(s-prefix "vcard:hasEmail"))
  		(:created :date ,(s-prefix "dcterms:created"))
  		(:modified :date ,(s-prefix "dcterms:modified")))
    :resource-base (s-url "http://data.bravoer.be/id/contacts/")
    :has-one `((address :via ,(s-prefix "locn:address")
  		      :as "address"))
  
negative.code:                 (:location :string ,(s-prefix "bravoer:libraryLocation"))
                  (:is-original :boolean ,(s-prefix "music:isOriginalScore"))
                  (:loan :string ,(s-prefix "music:loan"))
  		(:created :datetime ,(s-prefix "dcterms:created"))
  		(:modified :datetime ,(s-prefix "dcterms:modified")))
    :resource-base (s-url "http://data.bravoer.be/id/scores/")
    :has-many `((part :via ,(s-prefix "nie:isLogicalPartOf")
  			   :inverse t
  