```ruby
require_relative 'xml'

module Resync
  module XMLFactory

    ROOT_TYPES = [
      CapabilityList,
      ChangeDump,
      ChangeDumpManifest,
      ChangeList,
      ResourceDump,
      ResourceDumpManifest,
      ResourceList,
      SourceDescription
    ]

    CAPABILITY_ATTRIBUTE = "/*/[namespace-uri() = 'http://www.openarchives.org/rs/terms/' and local-name() = 'md']/@capability"

    def self.parse(xml:)
      root_element = XML.element(xml)
      capability = REXML::XPath.first(root_element, CAPABILITY_ATTRIBUTE).value
      root_type = ROOT_TYPES.find { |t| t::CAPABILITY == capability }
      root_type.load_from_xml(root_element)
    end

  end
end
```

Use alternate mapping when parsing sitemapindex
user
```ruby
require_relative 'xml'

module Resync
  module XMLFactory

    ROOT_TYPES = [
      CapabilityList,
      ChangeDump,
      ChangeDumpManifest,
      ChangeList,
      ResourceDump,
      ResourceDumpManifest,
      ResourceList,
      SourceDescription
    ]

    CAPABILITY_ATTRIBUTE = "/*/[namespace-uri() = 'http://www.openarchives.org/rs/terms/' and local-name() = 'md']/@capability"

    def self.parse(xml:)
      root_element = XML.element(xml)
      capability = REXML::XPath.first(root_element, CAPABILITY_ATTRIBUTE).value
      mapping = root_element.name == 'sitemapindex' ? :sitemapindex : :_default
      root_type = ROOT_TYPES.find { |t| t::CAPABILITY == capability }
      root_type.load_from_xml(root_element, mapping: mapping)
    end

  end
end
```
assistant