SOURCE PowrTagR Fedora CMA

From DigiRepWiki

CMA Object Variations (data, sDef, sDep, cModel):

• Data a container for content
  • data object has 3 parts: foxml:digitalObject, foxml:objectProperties,foxml:datastream
  • data may have many content models -> sDef operations
• Service Definition A container for service definitions, an element of a content model
  • sDef describes the Service and Operations it performs.
  • is an endpoint that may be called to execute operations <-OOP
  • to execute operation must identify data object, sDef and name of operation
    • Some operations use content form datastreams (supplied by the data object)
    • operation prescribed by client program or browser requestingexecution
  • way of saying 'this dataObject supports these operations
    • defines a 'behaviour contract'
  • sDef using identifier resolver system can be used by multiple repositories
• Service Deployment A container for the service deployment bindings
  • is local to repository, only operates with scope of local repo
    • can make amendments to sDef
  • represents how a service is implemented by the repository
  • sDep stores concrete service binding metadata
  • interprets to client which operators from the sDef that the sDep will deploy
  • describes the runtime binding for invoking service methods
  • WSDL used by Fedora to dispatch method requests for representations of DOs (via operations)
  • sDep contain contract between teh service and class of Data objects (as defined by cModel)
  • sDep objects are not freely shareable accross repositories by default
• Content Model A container for content models
  • operations for class' are similar, need to distinguish between operations and content class name
    • rather than directly reference sDef to data
  • All objects are organised into classes by CModel object.
  • data asserts its relation to cModel 'hasModel'
  • data should have datastream listed for each cModel it asserts
  • all objects assigned to default cModel which asserts basic sDef
  • A cModel is free to assert to more than one Service
  • A Service may be related to many cModels
• To GET item, syntax would be: Repository : Get : Data object PID : SDef PID : Operation Name : Optional Parameters

D's notes:

• better to think of CMA in terms of verbs (actions/operations) rather than nouns (objects).
• Some quotes from learned colleagues in regards to how to think about OOP:
  • twitter.com/jimdowning/status/1011278768
  • twitter.com/wee0ne/status/1011282807