Class: Skos2Html

Inherits:
Object
  • Object
show all
Defined in:
lib/skos2html.rb

Overview

Converts a SKOS RDF file to a bare-bones HTML file readabale for humans. Rendering a HTML file consists of three basic steps:

  1. Create a new instance of this class and specify input and output file.

  2. Call load_and_parse.

  3. Call generate_html_document.

  4. Call the write method.

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(infile = nil, outfile = "vocab.html") ⇒ Skos2Html

Initialize the class.

Parameters:

  • infile (String) (defaults to: nil) —

    , a filepath to a SKOS RDF/XML file

  • outfile (String) (defaults to: "vocab.html") —

    , a filepath where the resulting file will be written (overwriting existing files)



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# File 'lib/skos2html.rb', line 23

def initialize(infile=nil, outfile="vocab.html")
  @log = defined?(Rails) ? Rails.logger : Logger.new(STDOUT)
  @log.info("init")

  @infile = infile
  @outfile = outfile

  @default_lang = :en

  @graph = nil
  @vocabs = nil
  set_up_vocabs

  @buffer = ""
  @builder = Builder::XmlMarkup.new(:target=>@buffer, :indent=>2)

  @title = ""

end

Instance Attribute Details

#buffer ⇒ Object

The output buffer to which we write all HTML.



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# File 'lib/skos2html.rb', line 17

def buffer
  @buffer
end

Instance Method Details

#concept_scheme_title ⇒ Object

Get the title of this vocabulary for use in the HTML title element



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# File 'lib/skos2html.rb', line 301

def concept_scheme_title

  title_properties = ["http://purl.org/dc/terms/title",
      "http://www.w3.org/2000/01/rdf-schema#label",
      "http://www.w3.org/2004/02/skos/core#prefLabel"]

  title = ""

  conceptschemes = RDF::Query.execute(@graph) do
    pattern [:scheme, RDF.type, RDF::SKOS.ConceptScheme]
  end

  if conceptschemes.size == 1

    scheme = conceptschemes[0]
    @log.info("Looking for title for " + scheme.scheme)

    scheme_info = RDF::Query.execute(@graph) do
      pattern [scheme.scheme, :predicate, :object]
    end

    scheme_info.each do |solution|

      case solution.predicate.to_s
      when *title_properties
        title = solution.object.value
      end
    end

    return title

  end

end

#generate_concept(concept_uri) ⇒ Object

Generate the HTML for an individual concept.



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# File 'lib/skos2html.rb', line 339

def generate_concept(concept_uri)

  concept_info = RDF::Query.execute(@graph) do
    pattern [concept_uri, :predicate, :object]
  end

  preflabels = []
  altlabels = []
  definition = ""

  concept_info.each do |solution|

    case solution.predicate
    when "http://www.w3.org/2004/02/skos/core#prefLabel"
      if solution.object.language?
        preflabels << {"lang" => solution.object.language.to_sym, "val" => solution.object.to_s}
      else
        preflabels << {"lang" => nil, "val" => solution.object.to_s}
      end
    when "http://www.w3.org/2004/02/skos/core#altLabel"
      if solution.object.language?
        altlabels << {"lang" => solution.object.language.to_sym, "val" => solution.object.to_s}
      else
        altlabels << {"lang" => nil, "val" => solution.object.to_s}
      end
    when "http://www.w3.org/2004/02/skos/core#definition"
      definition = string_for(solution.object, @default_lang)
    end

  end


  @builder.div(:id => concept_uri.fragment, :class => "concept") { |html|
    # preflabel in defaultlang
    html.h2(preflabels.detect {|label| label["lang"] == @default_lang}["val"])
    html.dl {
      html.dt("Definition", :class => "definition")
      html.dd(definition, :class => "definition")

      if altlabels.size > 0
        html.dt("Alternative labels", {:class => "altlabels"})

        altlabels.each do |label|

          if label["lang"]

            if label["lang"] != @default_lang
              html.dd(label["val"] + "(#{label['lang']})", :lang => label["lang"], :class => "altlabel")
            else
              html.dd(label["val"], :class => "altlabel")
            end

          else
              html.dd(label["val"], :class => "altlabel")
          end
        end
      end

      html.dt("Identifier", :class => "identifier")
      html.dd(concept_uri, :class => "identifier")
    }
  }

end

#generate_concepts ⇒ Object 



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# File 'lib/skos2html.rb', line 283

def generate_concepts
  concepts = RDF::Query.execute(@graph) do
    pattern [:concept_uri, RDF.type, RDF::SKOS.Concept]
  end

  @log.info("Concept count: #{concepts.size}")

  concepts.each do |concept|
    generate_concept(concept.concept_uri)
  end

end

#generate_conceptscheme_info ⇒ Object 



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# File 'lib/skos2html.rb', line 199

def generate_conceptscheme_info

  conceptschemes = RDF::Query.execute(@graph) do
    pattern [:scheme, RDF.type, RDF::SKOS.ConceptScheme]
  end


  @log.info("Concept scheme count #{conceptschemes.size}")


  if conceptschemes.size == 1

    scheme = conceptschemes[0]
    @log.info("Looping concept scheme " + scheme.scheme)

    scheme_info = RDF::Query.execute(@graph) do
      pattern [scheme.scheme, :predicate, :object]
    end

    # Title
    title = ""

    # Description
    description = ""

    # Creators
    creators = []

    # Contributors
    contributors = []

    # get values
    scheme_info.each do |solution|

      case solution.predicate
      when "http://purl.org/dc/terms/title"
      when "http://www.w3.org/2000/01/rdf-schema#label"
        title = string_for(solution.object, @default_lang)
      when "http://purl.org/dc/terms/description"
        description = string_for(solution.object, @default_lang)
      when "http://purl.org/dc/terms/contributor"
        contributors << string_for(solution.object, nil)
      when "http://purl.org/dc/terms/creator"
        creators << string_for(solution.object, nil)
      end

    end

    @builder.div(:class => "conceptscheme") { |html|

      html.h1(title)

      html.dl { |html|

        html.dt("Description")
        html.dd(description, "class" => "description")

        if contributors.size > 0
          html.dt("Contributors")

          contributors.each do |item|
            html.dd(item, "class" => "contributor")
          end
        end

        if creators.size > 0
          html.dt("Creators")

          creators.each do |item|
            html.dd(item, "class" => "creator")
          end
        end

      }
    }

  else
    @log.info("Concept scheme count wrong. Expected 1 was " + conceptschemes.size)
  end

end

#generate_html_body ⇒ Object 



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# File 'lib/skos2html.rb', line 73

def generate_html_body
  @builder.body { |body|
    generate_conceptscheme_info
    generate_concepts
  }
end

#generate_html_document ⇒ Object 



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# File 'lib/skos2html.rb', line 63

def generate_html_document
  @builder.declare! :DOCTYPE, :html

  @builder.html(:lang => @default_lang) { |html|
    generate_html_head
    generate_html_body
  }
end

#generate_html_head ⇒ Object 



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# File 'lib/skos2html.rb', line 81

def generate_html_head

  title = concept_scheme_title

  @builder.head { |head|
    head.meta(:charset => "UTF-8")
    head.title(title)
    head.meta(:name => "generator", :content => "skos2html")
    head.style("""
html {
  margin: auto;
  max-width: 800px;
  font-family: Helvetica, Arial, sans-serif;
}

dt {
  font-weight: bold;
  margin: 0.8em 0 0.2em 0;
}

dd {
  margin: 0;
}

dd.contributor {
  display:inline;
}

dd.contributor:after { content: ', '; }
dd.contributor:last-child:after { content: ''; }

dd.identifier {
font-family: Consolas, 'Lucida Console', 'Courier New', sans-serif;
}

div.conceptscheme {
  border-bottom: 1px solid #aaa;
  margin: 1em 0 2em 0;
}

div.concept {
margin: 0 0 2.5em 0;
}
               """)
  }

end

#label_for(uri, lang) ⇒ Object 



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# File 'lib/skos2html.rb', line 178

def label_for(uri, lang)

  @log.info("label_for #{uri} #{lang}")

  labels = labels_for(uri)

  @log.info("labels: #{labels.inspect}")

  if labels
    labels.each do |label|

      @log.info("label: #{label}")

      if label.language == lang
        return label.value
      end
    end
  end
end

#labels_for(uri) ⇒ Object 



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# File 'lib/skos2html.rb', line 131

def labels_for(uri)

  solutions = RDF::Query.execute(@vocabs) do
    pattern [RDF::URI.new(uri), RDF::RDFS.label, :label]
  end

  result = []

  if solutions
    solutions.each do |solution|
      # adding RDF literals
      result << solution.label
    end
  end

  return result
end

#load_and_parse ⇒ Object

Load the SKOS RDF file into a graph object.



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# File 'lib/skos2html.rb', line 54

def load_and_parse

  if @infile
    @graph = RDF::Graph.load(@infile)
  end

end

#set_up_vocabs ⇒ Object

Load some basic vocabularies in order to retrieve labels etc.



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# File 'lib/skos2html.rb', line 46

def set_up_vocabs
  @vocabs = RDF::Graph.load(File.expand_path("skos.rdf", File.dirname(__FILE__)))
  @vocabs << RDF::Graph.load(File.expand_path("dcterms.rdf", File.dirname(__FILE__)))
  @vocabs << RDF::Graph.load(File.expand_path("rdf-schema.rdf", File.dirname(__FILE__)))
end

#string_for(obj, lang) ⇒ Object 



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# File 'lib/skos2html.rb', line 151

def string_for(obj, lang)
  # return a human readable representation of obj - for literals the literal
  # value in lang. For URI:s lookup something.

  case obj
  when String
    return obj
  when RDF::Literal
    if lang
      if obj.language == lang
        return obj.to_s
      else
        return "[Not available in #{lang}]"
      end
    else
      return obj.to_s
    end
  when RDF::URI
    # TODO: fetch it...
    return "[fetched label for #{obj.to_s}]"
  else
    @log.info("unknown class")
  end
end

#write ⇒ Object

Write the output to disk as an UTF-8 encoded file.



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# File 'lib/skos2html.rb', line 407

def write

  # output to disk
  File.open(@outfile, 'w:UTF-8') { |file|
    file.write(@buffer)
  }
end