text: from sqlalchemy import create_engine
  from sqlalchemy import Table, Column
  from sqlalchemy import Boolean, Integer, String, Text, DateTime
  from sqlalchemy import MetaData, ForeignKey
  
  from .config import Config
  
  metadata = MetaData()
  
  requests = Table('requests', metadata,
                   Column('request_id', Integer, primary_key=True),
                   Column('ppp_request_id', String),
                   Column('request_question', Text),
                   Column('request_datetime', DateTime),
                  )
  
  responses = Table('responses', metadata,
                    Column('response_id', Integer, primary_key=True),
                    Column('request_id', None, ForeignKey('requests.request_id')),
                    Column('parent_response_id', None, ForeignKey('responses.response_id'), nullable=True),
                    Column('response_is_final_result', Boolean),
                    Column('response_module', String),
                    Column('response_tree', Text),
                    Column('response_language', String),
                    Column('response_measures', Text),
                   )
  
  feedback = Table('feedback', metadata,
                   Column('feedback_id', Integer, primary_key=True),
                   Column('request_id', None, ForeignKey('requests.request_id')),
                   Column('response_is_good', Boolean),
                   Column('response_correction', Text),
                  )
  
  def get_engine(uri):
      """Asks SQLAlchemy to create an engine to connect to the URI and return it."""
      engine = create_engine(uri, echo=Config().debug)
      metadata.create_all(engine)
      return engine
  