def initialize(aws_access_key_id=nil, aws_secret_access_key=nil, params={})
@nil_rep = params[:nil_representation] ? params[:nil_representation] : DEFAULT_NIL_REPRESENTATION
params.delete(:nil_representation)
init({:name => 'SDB',
:default_host => ENV['SDB_URL'] ? URI.parse(ENV['SDB_URL']).host : DEFAULT_HOST,
:default_port => ENV['SDB_URL'] ? URI.parse(ENV['SDB_URL']).port : DEFAULT_PORT,
:default_protocol => ENV['SDB_URL'] ? URI.parse(ENV['SDB_URL']).scheme : DEFAULT_PROTOCOL,
:default_service => ENV['SDB_URL'] ? URI.parse(ENV['SDB_URL']).path : DEFAULT_SERVICE},
aws_access_key_id || ENV['AWS_ACCESS_KEY_ID'],
aws_secret_access_key || ENV['AWS_SECRET_ACCESS_KEY'],
params)
end