ISO Schematron

% gem install schematron

% stron my_schema.stron my_xml_document.xml

# overhead
require "libxml"
require "schematron"

include LibXML

# load the schematron xml
stron_doc = XML::Document.file "/path/to/my_schema.stron"

# make a schematron object
stron = Schematron::Schema.new stron_doc

# load the xml document you wish to validate
xml_doc = XML::Document.file "/path/to/my_xml_document.xml"

# validate it
results = stron.validate xml_doc

# print out the results
stron.validate(instance_doc).each do |error|
  puts "#{error[:line]}: #{error[:message]}"
end