Metacat

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  \newpage

Identifier Management

---------------------

.. index:: Identifiers

Author

  Matthew B. Jones

Date

  - 20100301 [MBJ] Initial draft of Identifier documentation

Goal

  Extend Metacat to support identifiers with arbitrary syntax

Summary 

  Metacat currently supports identifier strings called 'docids' that have

  the syntax 'scope.object.revision', such as 'foo.34.1' (we will refer to

  these as 'LocalIDs'). We now want Metacat to support identifiers that are 

  arbitrary strings, but still enforce uniqueness and proper revision

  handling (referred to these as GUIDs).  Metacat must be able to accept 

  these strings as identifiers for all CRUD operations, and reference them 

  in search results.

Identifier Resolution

=====================

Because Metacat uses LocalIDs throughout the code for references to objects,

and that LocalID has a constrained structure that includes semantics about

revisions in the identifier, it is difficult to wholesale replace it with

less-constrained string identifiers without re-writing much of Metacat.

Thus, our alternate strategy would is to wrap the Metacat APIs with a

identifier resolution layer that keeps track of the unconstrained GUIDs and

maps them to constrained local identifiers which are used internally within

Metacat. The basic identifer table model is shown in Figure 1, while the

basic strategy for retrieving an object is shown in Figure 2.

Identifier Table Structure

~~~~~~~~~~~~~~~~~~~~~~~~~~

.. figure:: images/identifiers.png

   Figure 1. Table structure for identifiers.

..

  This block defines the table structure diagram referenced above.

  @startuml images/identifiers.png

  identifiers "*" -- "1" xml_documents

  identifiers : String identifier

  identifiers : String docid

  identifiers : Integer rev

  xml_documents : String docid

  xml_documents : String rev

  note right of identifiers

    "identifiers.(docid,rev) is a foreign key into xml_documents"

  end note

  @enduml

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  \newpage

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  PageBreak

Handling document read operations

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

An overview of the process needed to read an object using a GUID.

.. figure:: images/guid_read.png

   Figure 2. Basic handling for string identifiers (GUIDs) as mapped to

   docids (LocalIDs) to retrieve an object.

..

  @startuml images/guid_read.png

  !include plantuml.conf

  actor User

  participant "Client" as app_client << Application >>

  participant "CRUD API" as c_crud << MetacatRestServlet >>

  participant "Identifier Manager" as ident_man << IdentifierManager >>

  participant "Handler" as handler << MetacatHandler >>

  User -> app_client

  app_client -> c_crud: get(token, GUID)

  c_crud -> ident_man: getLocalID(GUID)

  c_crud <-- ident_man: localID

  c_crud -> handler: handleReadAction(localID)

  c_crud <-- handler: object

  c_crud --> app_client: object

  @enduml

Handling document create operations

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

An overview of the process needed to create an object using a GUID.

.. figure:: images/guid_insert.png

   Figure 3. Basic handling for string identifiers (GUIDs) as mapped to

   docids (LocalIDs) to create an object.

..

  @startuml images/guid_insert.png

  !include plantuml.conf

  actor User

  participant "Client" as app_client << Application >>

  participant "CRUD API" as c_crud << MetacatRestServlet >>

  participant "Identifier Manager" as ident_man << IdentifierManager >>

  participant "Handler" as handler << MetacatHandler >>

  User -> app_client

  app_client -> c_crud: create(token, GUID, object, sysmeta)

  c_crud -> ident_man: identifierExists(GUID)

  c_crud <-- ident_man: T or F 

  alt identifierExists == "F"

      c_crud -> ident_man: mapToLocalId(GUID)

      c_crud <-- ident_man: localID

      c_crud -> handler: handleInsertAction(localID)

      c_crud <-- handler: success

      note right of c_crud

        "Also need to address how to handle the sysmeta information wrt insertion methods"

      end note

      app_client <-- c_crud: success

  else identifierExists == "T"

      app_client <-- c_crud: IdentifierNotUnique

  end

  @enduml

Handling document update operations

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

An overview of the process needed to update an object using a GUID.

.. figure:: images/guid_update.png

   Figure 4. Basic handling for string identifiers (GUIDs) as mapped to

   docids (LocalIDs) to update an object.

..

  @startuml images/guid_update.png

  !include plantuml.conf

  actor User

  participant "Client" as app_client << Application >>

  participant "CRUD API" as c_crud << MetacatRestServlet >>

  participant "Identifier Manager" as ident_man << IdentifierManager >>

  participant "Handler" as handler << MetacatHandler >>

  User -> app_client

  app_client -> c_crud: update(token, GUID, object, obsoletedGUID, sysmeta)

  c_crud -> ident_man: identifierExists(obsoletedGUID)

  c_crud <-- ident_man: T or F 

  alt identifierExists == "T"

      c_crud -> ident_man: identifierExists(GUID)

      c_crud <-- ident_man: T or F 

      alt identifierExists == "F"

          c_crud -> ident_man: mapToLocalId(GUID, obsoletedGUID)

          c_crud <-- ident_man: localID

          c_crud -> handler: handleUpdateAction(localID)

          c_crud <-- handler: success

          note right of c_crud

            "Also need to address how to handle the sysmeta information wrt update methods"

          end note

          app_client <-- c_crud: success

      else identifierExists == "T"

          app_client <-- c_crud: IdentifierNotUnique

      end

  else identifierExists == "F"

      app_client <-- c_crud: NotFound

  end

  @enduml

Handling document delete operations

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

An overview of the process needed to delete an object using a GUID.

.. figure:: images/guid_delete.png

   Figure 5. Basic handling for string identifiers (GUIDs) as mapped to

   docids (LocalIDs) to delete an object.

..

  @startuml images/guid_delete.png

  !include plantuml.conf

  actor User

  participant "Client" as app_client << Application >>

  participant "CRUD API" as c_crud << MetacatRestServlet >>

  participant "Identifier Manager" as ident_man << IdentifierManager >>

  participant "Handler" as handler << MetacatHandler >>

  User -> app_client

  app_client -> c_crud: delete(token, GUID)

  c_crud -> ident_man: identifierExists(GUID)

  c_crud <-- ident_man: T or F 

  alt identifierExists == "T"

      c_crud -> ident_man: mapToLocalId(GUID)

      c_crud <-- ident_man: localID

      c_crud -> handler: handleDeleteAction(localID)

      c_crud <-- handler: success

      app_client <-- c_crud: success

  else identifierExists == "F"

      app_client <-- c_crud: NotFound

  end

  @enduml

..

  This block defines the interaction diagram referenced above.

  startuml images/01_interaction.png

    !include plantuml.conf

    actor User

    participant "Client" as app_client << Application >>

    User -> app_client

    participant "CRUD API" as c_crud << Coordinating Node >>

    activate c_crud

    app_client -> c_crud: resolve(GUID, auth_token)

    participant "Authorization API" as c_authorize << Coordinating Node >>

    c_crud -> c_authorize: isAuth(auth_token, GUID)

    participant "Verify API" as c_ver << Coordinating Node >>

    c_authorize -> c_ver: isValidToken (token)

    c_authorize <-- c_ver: T or F

    c_crud <-- c_authorize: T or F

    app_client <-- c_crud: handle_list

    deactivate c_crud

    participant "CRUD API" as m_crud << Member Node >>

    activate m_crud

    app_client -> m_crud: get(auth_token, handle)

    participant "Server Authentication API" as m_authenticate << Member Node >>

    m_crud -> m_authenticate: isAuth(auth_token, GUID)

    m_crud <-- m_authenticate: T or F

    m_crud -> m_crud: log(get, UserID, GUID)

    app_client <-- m_crud: object or unauth or doesNotExist

    deactivate m_crud

  enduml