new (DataMapper::Migration)

    # File lib/dm-migrations/migration.rb, line 17
        def initialize( position, name, opts = {}, &block )
          @position, @name = position, name
          @options = opts

          @database = DataMapper.repository(@options[:database] || :default)
          @adapter = @database.adapter

          case @adapter.class.to_s
          when /Sqlite3/  then @adapter.extend(SQL::Sqlite3)
          when /Mysql/    then @adapter.extend(SQL::Mysql)
          when /Postgres/ then @adapter.extend(SQL::Postgresql)
          else
            raise "Unsupported Migration Adapter #{@adapter.class}"
          end

          @verbose = @options.has_key?(:verbose) ? @options[:verbose] : true

          @up_action   = lambda {}
          @down_action = lambda {}

          instance_eval &block
        end