globals.py

"""
Copyright 2015, University of Freiburg.

Elmar Haussmann <haussmann@cs.uni-freiburg.de>
"""
from ConfigParser import SafeConfigParser
from itertools import tee, izip
import logging

logger = logging.getLogger(__name__)

FREEBASE_NS_PREFIX = "http://rdf.freebase.com/ns/"
FREEBASE_SPARQL_PREFIX = "fb"
FREEBASE_NAME_RELATION = "type.object.name"
FREEBASE_KEY_PREFIX = "http://rdf.freebase.com/key/"

sparql_backend = None
# When a configuration is read, store it here to make it accessible.
config = None

# TODO(elmar): move this somewhere else.
def get_sparql_backend(config_options):
    global sparql_backend
    from sparql_backend.backend import  SPARQLHTTPBackend
    if not sparql_backend:
        sparql_backend = SPARQLHTTPBackend.init_from_config(config_options)
    return sparql_backend


def get_prefixed_qualified_mid(mid, prefix):
    return "%s:%s" % (prefix, mid)


def read_configuration(configfile):
    """Read configuration and set variables.

    :return:
    """
    global config
    logger.info("Reading configuration from: " + configfile)
    parser = SafeConfigParser()
    parser.read(configfile)
    config = parser
    return parser

def get_qualified_mid(mid):
    '''
    Returns a fully qualified MID, with NS
    prefix and brackets.
    :param mid:
    :return:
    '''
    return "<%s%s>" % (FREEBASE_NS_PREFIX, mid)

def get_mid_from_qualified_string(qualified_str):
    '''
    Returns a fully qualified MID, with NS
    prefix and brackets.
    :param mid:
    :return:
    '''
    if qualified_str.startswith('<') and qualified_str.endswith('>'):
        qualified_str = qualified_str[1:-1]
    return remove_freebase_ns(qualified_str)

def remove_freebase_ns(mid):
    '''
    Returns a fully qualified MID, with NS
    prefix and brackets.
    :param mid:
    :return:
    '''
    if mid.startswith(FREEBASE_NS_PREFIX):
        return mid[len(FREEBASE_NS_PREFIX):]
    return mid

def pairwise(iterable):
    a, b = tee(iterable)
    next(b, None)
    return izip(a, b)


def get_freebase_easy_name_for_freebase_relation_suffix(fb_suffix):
    '''
    Return the Freebase easy name for a freebase relation suffix,
    e.g. people.person.born_in -> people/person/born_in
    :param fb_suffix:
    :return:
    '''
    fb_suffix = fb_suffix.replace('.', '/')
    return fb_suffix