Class: JSON::LD::API

Inherits:
Object
  • Object
show all
Includes:
Compact, Expand, Frame, FromTriples, Triples
Defined in:
lib/json/ld/api.rb

Overview

A JSON-LD processor implementing the JsonLdProcessor interface.

This API provides a clean mechanism that enables developers to convert JSON-LD data into a a variety of output formats that are easier to work with in various programming languages. If a JSON-LD API is provided in a programming environment, the entirety of the following API must be implemented.

See Also:

Author:

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Methods included from Frame

#cleanup_preserve, #flatten, #frame, #get_framing_subjects, #remove_dependents

Methods included from Utils

#blank_node?, #list?, #subject?, #subject_reference?, #value?

Methods included from FromTriples

#from_statements

Methods included from Triples

#add_quad, #node, #parse_list, #statements

Methods included from Compact

#compact

Methods included from Expand

#expand

Constructor Details

#initialize(input, context, options = {}) {|api| ... } ⇒ API

Initialize the API, reading in any document and setting global options

Parameters:

  • input (String, #read, Hash, Array)
  • context (String, #read, , Hash, Array) —

    An external context to use additionally to the context embedded in input when expanding the input.

  • options (Hash) (defaults to: {})

Yields:

  • (api)

Yield Parameters:



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# File 'lib/json/ld/api.rb', line 37

def initialize(input, context, options = {}, &block)
  @options = options
  @value = case input
  when Array, Hash then input.dup
  when IO, StringIO then JSON.parse(input.read)
  when String
    content = nil
    RDF::Util::File.open_file(input) {|f| content = JSON.parse(f.read)}
    content
  end
  @context = EvaluationContext.new(options)
  @context = @context.parse(context) if context
  
  if block_given?
    case block.arity
      when 0, -1 then instance_eval(&block)
      else block.call(self)
    end
  end
end

Instance Attribute Details

#context ⇒ Object

Returns the value of attribute context.



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# File 'lib/json/ld/api.rb', line 26

def context
  @context
end

#value ⇒ Object

Returns the value of attribute value.



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# File 'lib/json/ld/api.rb', line 25

def value
  @value
end

Class Method Details

.compact(input, context, callback = nil, options = {}) {|jsonld| ... } ⇒ Hash

Compacts the given input according to the steps in the Compaction Algorithm. The input must be copied, compacted and returned if there are no errors. If the compaction fails, an appropirate exception must be thrown.

If no context is provided, the input document is compacted using the top-level context of the document

The resulting ‘Hash` is returned via the provided callback.

Note that for Ruby, if the callback is not provided and a block is given, it will be yielded

Parameters:

  • input (String, #read, Hash, Array) —

    The JSON-LD object to copy and perform the compaction upon.

  • context (String, #read, Hash, Array) —

    The base context to use when compacting the input.

  • callback (Proc) (defaults to: nil) —

    (&block) Alternative to using block, with same parameters.

  • options (Hash{Symbol => Object}) (defaults to: {}) —

    Other options passed to Expand#expand

Options Hash (options):

  • :optimize (Boolean) — default: false —

    Perform further optimmization of the compacted output. (Presently, this is a noop).

Yields:

  • jsonld

Yield Parameters:

  • jsonld (Hash) —

    The compacted JSON-LD document

Returns:

  • (Hash) —

    The compacted JSON-LD document

Raises:

See Also:



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# File 'lib/json/ld/api.rb', line 127

def self.compact(input, context, callback = nil, options = {})
  expanded = result = nil

  # 1) Perform the Expansion Algorithm on the JSON-LD input.
  #    This removes any existing context to allow the given context to be cleanly applied.
  expanded = API.expand(input, nil, nil, options)

  API.new(expanded, context, options) do
    debug(".compact") {"expanded input: #{expanded.to_json(JSON_STATE)}"}
    result = compact(value, nil)

    # xxx) Add the given context to the output
    result = case result
    when Hash then self.context.serialize.merge(result)
    when Array
      kwgraph = self.context.compact_iri('@graph', :quiet => true)
      self.context.serialize.merge(kwgraph => result)
    when String
      kwid = self.context.compact_iri('@id', :quiet => true)
      self.context.serialize.merge(kwid => result)
    end
  end
  callback.call(result) if callback
  yield result if block_given?
  result
end

.expand(input, context = nil, callback = nil, options = {}) {|jsonld| ... } ⇒ Array<Hash>

Expands the given input according to the steps in the Expansion Algorithm. The input must be copied, expanded and returned if there are no errors. If the expansion fails, an appropriate exception must be thrown.

The resulting ‘Array` is returned via the provided callback.

Note that for Ruby, if the callback is not provided and a block is given, it will be yielded

Parameters:

  • input (String, #read, Hash, Array) —

    The JSON-LD object to copy and perform the expansion upon.

  • context (String, #read, Hash, Array) (defaults to: nil) —

    An external context to use additionally to the context embedded in input when expanding the input.

  • callback (Proc) (defaults to: nil) —

    (&block) Alternative to using block, with same parameters.

  • options (Hash{Symbol => Object}) (defaults to: {})

Options Hash (options):

  • :base (Boolean) —

    Base IRI to use when processing relative IRIs.

Yields:

  • jsonld

Yield Parameters:

  • jsonld (Array<Hash>) —

    The expanded JSON-LD document

Returns:

  • (Array<Hash>) —

    The expanded JSON-LD document

Raises:

See Also:



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# File 'lib/json/ld/api.rb', line 82

def self.expand(input, context = nil, callback = nil, options = {})
  result = nil
  API.new(input, context, options) do |api|
    result = api.expand(api.value, nil, api.context)
  end

  # If, after the algorithm outlined above is run, the resulting element is an
  # JSON object with just a @graph property, element is set to the value of @graph's value.
  result = result['@graph'] if result.is_a?(Hash) && result.keys == %w(@graph)

  # Finally, if element is a JSON object, it is wrapped into an array.
  result = [result] unless result.is_a?(Array)
  callback.call(result) if callback
  yield result if block_given?
  result
end

.frame(input, frame, callback = nil, options = {}) {|jsonld| ... } ⇒ Array<Hash>

Frames the given input using the frame according to the steps in the Framing Algorithm. The input is used to build the framed output and is returned if there are no errors. If there are no matches for the frame, null must be returned. Exceptions must be thrown if there are errors.

The resulting ‘Array` is returned via the provided callback.

Note that for Ruby, if the callback is not provided and a block is given, it will be yielded

Parameters:

  • input (String, #read, Hash, Array) —

    The JSON-LD object to copy and perform the framing on.

  • frame (String, #read, Hash, Array) —

    The frame to use when re-arranging the data.

  • callback (Proc) (defaults to: nil) —

    (&block) Alternative to using block, with same parameters.

  • options (Hash{Symbol => Object}) (defaults to: {}) —

    Other options passed to Expand#expand

Options Hash (options):

  • :embed (Boolean) — default: true —

    a flag specifying that objects should be directly embedded in the output, instead of being referred to by their IRI.

  • :explicit (Boolean) — default: false —

    a flag specifying that for properties to be included in the output, they must be explicitly declared in the framing context.

  • :omitDefault (Boolean) — default: false —

    a flag specifying that properties that are missing from the JSON-LD input should be omitted from the output.

Yields:

  • jsonld

Yield Parameters:

  • jsonld (Hash) —

    The framed JSON-LD document

Returns:

  • (Array<Hash>) —

    The framed JSON-LD document

Raises:

See Also:



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# File 'lib/json/ld/api.rb', line 187

def self.frame(input, frame, callback = nil, options = {})
  result = nil
  match_limit = 0
  framing_state = {
    :embed       => true,
    :explicit    => false,
    :omitDefault => false,
    :embeds      => nil,
  }
  framing_state[:embed] = options[:embed] if options.has_key?(:embed)
  framing_state[:explicit] = options[:explicit] if options.has_key?(:explicit)
  framing_state[:omitDefault] = options[:omitDefault] if options.has_key?(:omitDefault)

  # de-reference frame to create the framing object
  frame = case frame
  when Hash then frame.dup
  when IO, StringIO then JSON.parse(frame.read)
  when String
    content = nil
    RDF::Util::File.open_file(frame) {|f| content = JSON.parse(f.read)}
    content
  end

  # Expand frame to simplify processing
  expanded_frame = API.expand(frame)
  
  # Expand input to simplify processing
  expanded_input = API.expand(input)

  # Initialize input using frame as context
  API.new(expanded_input, nil, options) do
    debug(".frame") {"context from frame: #{context.inspect}"}
    debug(".frame") {"expanded frame: #{expanded_frame.to_json(JSON_STATE)}"}
    debug(".frame") {"expanded input: #{value.to_json(JSON_STATE)}"}

    # Get framing subjects from expanded input, replacing Blank Node identifiers as necessary
    @subjects = Hash.ordered
    depth {get_framing_subjects(@subjects, value, BlankNodeNamer.new("t"))}
    debug(".frame") {"subjects: #{@subjects.to_json(JSON_STATE)}"}

    result = []
    frame(framing_state, @subjects, expanded_frame[0], result, nil)
    debug(".frame") {"after frame: #{result.to_json(JSON_STATE)}"}
    
    # Initalize context from frame
    @context = depth {@context.parse(frame['@context'])}
    # Compact result
    compacted = depth {compact(result, nil)}
    compacted = [compacted] unless compacted.is_a?(Array)

    # Add the given context to the output
    kwgraph = context.compact_iri('@graph', :quiet => true)
    result = context.serialize.merge({kwgraph => compacted})
    debug(".frame") {"after compact: #{result.to_json(JSON_STATE)}"}
    result = cleanup_preserve(result)
  end

  callback.call(result) if callback
  yield result if block_given?
  result
end

.fromRDF(input, callback = nil, options = {}) {|jsonld| ... } ⇒ Array<Hash>

Take an ordered list of RDF::Statements and turn them into a JSON-LD document.

The resulting ‘Array` is returned via the provided callback.

Note that for Ruby, if the callback is not provided and a block is given, it will be yielded

Parameters:

  • input (Array<RDF::Statement>)
  • callback (Proc) (defaults to: nil) —

    (&block) Alternative to using block, with same parameteres.

  • options (Hash{Symbol => Object}) (defaults to: {})

Options Hash (options):

  • :notType (Boolean) —

    don’t use @type for rdf:type

Yields:

  • jsonld

Yield Parameters:

  • jsonld (Hash) —

    The JSON-LD document in expanded form

Returns:

  • (Array<Hash>) —

    The JSON-LD document in expanded form



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# File 'lib/json/ld/api.rb', line 297

def self.fromRDF(input, callback = nil, options = {})
  result = nil

  API.new(nil, nil, options) do |api|
    result = api.from_statements(input)
  end

  callback.call(result) if callback
  yield result if block_given?
  result
end

.toRDF(input, context = nil, callback = nil, options = {}) {|statement| ... } ⇒ Object

Processes the input according to the RDF Conversion Algorithm, calling the provided callback for each triple generated.

Note that for Ruby, if the callback is not provided and a block is given, it will be yielded

Parameters:

  • input (String, #read, Hash, Array) —

    The JSON-LD object to process when outputting statements.

  • context (String, #read, Hash, Array) (defaults to: nil) —

    An external context to use additionally to the context embedded in input when expanding the input.

  • callback (Proc) (defaults to: nil) —

    (&block) Alternative to using block, with same parameteres.

  • options ({Symbol,String => Object}) (defaults to: {}) —

    Options passed to Expand#expand

Yields:

  • statement

Yield Parameters:

  • statement (RDF::Statement)

Raises:



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# File 'lib/json/ld/api.rb', line 265

def self.toRDF(input, context = nil, callback = nil, options = {})
  # 1) Perform the Expansion Algorithm on the JSON-LD input.
  #    This removes any existing context to allow the given context to be cleanly applied.
  expanded = expand(input, context, nil, options)

  API.new(expanded, nil, options) do
    debug(".expand") {"expanded input: #{value.to_json(JSON_STATE)}"}
    # Start generating statements
    statements("", value, nil, nil, nil) do |statement|
      callback.call(statement) if callback
      yield statement if block_given?
    end
  end
end