Ruby script to detect default namespace declaration in an OAI-PMH response containing metadata records in ISO/TS 19139. Output is tab-separated text containing lines with two columns of (1) last namespace URI and (2) gmd:fileIdentifier/*/text(). Tested with ruby-1.8.7, libxml-ruby 1.1.3, and libxml2 20706.

nsdecl.rb

require 'rubygems'
require 'xml'

include XML

class Scanner

  def initialize parent
    @parent = parent
    @reader = @xpath = nil
  end

  def check_atts
    n = @reader.attribute_count
    @reader.move_to_first_attribute
    n.times do
      if @reader.namespace_declaration?
        @parent.nsdecl(@reader.name, @reader.value)
      end
      @reader.move_to_next_attribute
    end
  end

  def open_tag
    @xpath.push [@reader.local_name, @reader.namespace_uri]
    @parent.open_rec if @parent.md_metadata?(@xpath)
  end

  def close_tag nametest = nil
    @parent.close_rec if @parent.md_metadata?(@xpath)
    name = @xpath.pop.first
    return unless nametest
    raise "BadXML <#{name}>...</#{nametest}>" unless name == nametest
  end

  def scanfile fpath
    @reader = Reader.file(fpath)
    @xpath = []
    while @reader.read
      case @reader.node_type
      when Reader::TYPE_TEXT
	@parent.fid = @reader.value if @parent.fileIdentifier?(@xpath)
      when Reader::TYPE_ELEMENT
        open_tag
	emptyp = @reader.empty_element?
	check_atts if @reader.has_attributes?
	close_tag if emptyp
      when Reader::TYPE_END_ELEMENT
        close_tag @reader.local_name
      end
    end
  end

end

class App

  def initialize
    @scanner = Scanner.new(self)
    @rec = nil
    @count = 0
  end

  def open_rec
    close_rec if @rec
    @count += 1
    @rec = {:nr => @count}
  end

  def close_rec
    return unless @rec
    puts [@rec['xmlns'], @rec[:fid]].join("\t") if @rec['xmlns']
    @rec = nil
  end

  def arg args
    @scanner.scanfile args
    close_rec
  end

  def fileIdentifier? xpath
    xpath[-2] == ['fileIdentifier', 'http://www.isotc211.org/2005/gmd']
  end

  def fid= fid
    @rec[:fid] = fid
  end

  def md_metadata? xpath
    xpath[-2] == ['metadata', 'http://www.openarchives.org/OAI/2.0/']
  end

  def nsdecl prefix, uri
    return unless @rec
    @rec[prefix] = uri
  end

end

app = App.new
ARGV.each {|args| app.arg(args) }