Class: RDF::LDP::DirectContainer

Inherits:
Container show all
Defined in:
lib/rdf/ldp/direct_container.rb

Overview

An extension of ‘RDF::LDP::Container` implementing direct containment. This adds the concepts of a membership resource, predicate, and triples to the Basic Container’s containment triples.

When the membership resource is an ‘RDFSource`, the membership triple is added/removed from its graph when the resource created/deleted within the container. When the membership resource is a `NonRDFSource`, the triple is added/removed on its description’s graph instead.

A membership constant URI and membership predicate MUST be specified as described in LDP–exactly one of each. If none is given, we default to the container itself as a membership resource and ‘ldp:member` as predicate. If more than one of either is given, all `#add/#remove` (POST/DELETE) requests will fail.

See Also:

Direct Known Subclasses

IndirectContainer

Constant Summary collapse

MEMBER_URI = 
RDF::Vocab::LDP.member.freeze
MEMBERSHIP_RESOURCE_URI = 
RDF::Vocab::LDP.membershipResource.freeze
RELATION_TERMS = 
[RDF::Vocab::LDP.hasMemberRelation.freeze,
RDF::Vocab::LDP.isMemberOfRelation.freeze].freeze

Constants inherited from Resource

Resource::CONTAINS_URI, Resource::INVALIDATED_AT_URI, Resource::MODIFIED_URI

Instance Attribute Summary

Attributes inherited from Resource

#metagraph, #subject_uri

Class Method Summary collapse

Instance Method Summary collapse

Methods inherited from Container

#add_containment_triple, #container?, #containment_triples, #has_containment_triple?, #make_containment_triple, #remove_containment_triple, #update

Methods inherited from RDFSource

#destroy, #graph, #initialize, #rdf_source?, #to_response, #update

Methods inherited from Resource

#allowed_methods, #container?, #containers, #destroy, #destroyed?, #etag, #exists?, find, gen_id, #initialize, interaction_model, #last_modified, #ldp_resource?, #match?, metagraph_name, #non_rdf_source?, #rdf_source?, #request, #to_response, #to_uri, #update

Constructor Details

This class inherits a constructor from RDF::LDP::RDFSource

Class Method Details

.to_uri ⇒ Object 



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# File 'lib/rdf/ldp/direct_container.rb', line 27

def self.to_uri
  RDF::Vocab::LDP.DirectContainer
end

Instance Method Details

#add(resource, transaction = nil) ⇒ Object

Adds a member ‘resource` to the container. Handles containment and adds membership triple to the memebership resource.

See Also:



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# File 'lib/rdf/ldp/direct_container.rb', line 67

def add(resource, transaction = nil)
  process_membership_resource(resource,
                              transaction) do |container, quad, subject|
    super(subject, transaction) # super handles nil transaction case
    target = transaction || container.graph
    target.insert(quad)
  end
  self
end

#container_class ⇒ RDF::URI

Returns a URI representing the container type.

Returns:

  • (RDF::URI) —

    a URI representing the container type



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# File 'lib/rdf/ldp/direct_container.rb', line 33

def container_class
  CONTAINER_CLASSES[:direct]
end

#create(input, content_type) ⇒ Object

TODO:

Make atomic. Consider just raising an error instead of adding triples. There’s a need to handle this issue for repositories with snapshot reads, as well as those without.

Note:

the addition of default triples is handled in a separate transaction. It is possible for the second transaction to fail, causing the resource to persist in an invalid state. It is also possible for a read to occur between the two transactions.

Creates and inserts default relation triples if none are given.

See Also:



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# File 'lib/rdf/ldp/direct_container.rb', line 49

def create(input, content_type)
  super

  graph.transaction(mutable: true) do |tx|
    tx.insert(default_member_relation_statement) if
      member_relation_statements.empty?
    tx.insert(default_membership_resource_statement) if
      membership_resource_statements.empty?
  end

  self
end

#make_membership_triple(resource) ⇒ RDF::URI

Returns the membership triple representing membership of the ‘resource` parameter in this container.

Parameters:

  • resource (RDF::Term) —

    a member for this container

Returns:

  • (RDF::URI) —

    the membership triple representing membership of the ‘resource` parameter in this container

See Also:



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# File 'lib/rdf/ldp/direct_container.rb', line 134

def make_membership_triple(resource)
  predicate = membership_predicate
  return RDF::Statement(membership_constant_uri, predicate, resource) if
    member_relation_statements.first.predicate == RELATION_TERMS.first
  RDF::Statement(resource, predicate, membership_constant_uri)
end

#membership_constant_uri ⇒ RDF::URI

Gives the membership constant URI. If none is present in the container state, we add the current resource as a membership constant.

Returns:

  • (RDF::URI) —

    the membership constant uri for the container

Raises:

See Also:



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# File 'lib/rdf/ldp/direct_container.rb', line 102

def membership_constant_uri
  statements = membership_resource_statements
  return statements.first.object if statements.count == 1

  raise(NotAcceptable, 'An LDP-DC MUST have exactly one membership ' \
                       "resource; found #{statements.count}.")
end

#membership_predicate ⇒ RDF::URI

Gives the membership predicate. If none is present in the container state, we add the current resource as a membership constant.

Returns:

  • (RDF::URI) —

    the membership predicate

Raises:

See Also:



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# File 'lib/rdf/ldp/direct_container.rb', line 119

def membership_predicate
  statements = member_relation_statements
  return statements.first.object if statements.count == 1

  raise(NotAcceptable, 'An LDP-DC MUST have exactly one member ' \
                       "relation triple; found #{statements.count}.")
end

#remove(resource, transaction = nil) ⇒ Object

Removes a member ‘resource` to the container. Handles containment and removes membership triple to the memebership resource.

See Also:



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# File 'lib/rdf/ldp/direct_container.rb', line 82

def remove(resource, transaction = nil)
  process_membership_resource(resource,
                              transaction) do |container, quad, subject|
    super(subject, transaction) # super handles nil transaction case
    target = transaction || container.graph
    target.delete(quad)
  end
  self
end