anchor.diff:  
   SPRING ..> S : manages
   DS "is a"-u-> S
  -DS --> A : contributes\n 1..*\n
  +DS --> A : has 1..*
   @enduml
   --
   
  -*_Viewmodels_* and *_Entities_* are specializations of *_Domain-Objects_*. 
  +*_Viewmodels_* and *_Entities_* are specializations of *_Domain Objects_*. 
   
  -_Domain-Objects_ have *_Properties_*, *_Collections_* and *_Actions_*, 
  +_Domain Objects_ have *_Properties_*, *_Collections_* and *_Actions_*, 
   while _Viewmodels_ are (lifecycle-) managed by _Apache Isis_, 
   _Entities_ are managed by the configured persistence layer 
   (either JDO or JPA).
   
  -*_Services_* in general are (lifecycle-) managed by _Spring_. 
  -We distinguish between _Services_ that *_contribute_* to the metamodel
  -and those that don't. Contributing _Services_ we call *_Domain-Services_*. 
  -Those do contribute _Actions_ to the metamodel. 
  +*_Services_* in general are (lifecycle-) managed by _Spring_.
  +We distinguish between _Services_ that are *_included_* in the metamodel
  +and those that are not. Included _Services_ we call *_Domain Services_*,
  +and their _Actions_ (like _Domain Objects_) are part of the metamodel.
  +
   Those _Actions_ are either visible as _Menu Actions_ in the UI 
   and/or made available for the _Restful Objects Viewer_. 
   (As indicated by the so called _Service's_ *_Nature_*.)
   
  -*_Mixins_* do contribute either a _Property_, a _Collection_ 
  +*_Mixins_* do *_contribute_* either a _Property_, a _Collection_ 
   or an _Action_ to their *_Mixee_* (-type). 
  
positive.code: (Service) as S
  (Domain\nService) as DS
  (<i>Spring</i>) as SPRING
  (Member) as MB
  (Property) as P
  (Collection) as C
  (Action) as A
  
  together {
      DO <-d-"is a" VM
      DO <-d-"is a" E
      FW .u.> VM : manages
      PL .u.> E : manages
  }
  
  together {
      P "is a"-u-> MB
      C "is a"-u-> MB
      A "is a"-u-> MB
  }
  DO --> MB : has 1..*
  
  M "contributes\n a"..> MB
  
negative.code: skinparam nodesep 20
  skinparam ranksep 1
  
  together {
  	(Domain\nObject) as DO
  	(Entity) as E
  	(View\nModel) as VM
  }
  (<i>Apache Isis</i>) as FW
  (Persistence\nLayer) as PL
  together {
  