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'''
Created on 24 Sep 2011
@author: cgueret
'''
# python import
import httplib, time
# rdflib import
from rdflib_ import ConjunctiveGraph, RDF, URIRef, Namespace, Literal
# semanticxo import
from semanticxo.sparql import SPARQL
OLPC = Namespace("http://example.org/")
OLPC_TERMS = Namespace("http://example.org/terms#")
_QUERY_INT_KEY = ['timestamp', 'filesize', 'creation_time']
class TripleStore(object):
'''
The TripleStore is a generic object interface with a triple store
'''
def __init__(self, hostname=None):
'''
Constructor of the TripleStore
if an hostname is indicated, query the triple store of that machine
instead of the one at localhost
'''
if hostname == None:
hostname = 'localhost'
self.store_url = '%s:8080' % hostname
self.device_uid = 'ABC1234567890' #TODO find how to get the serial number
def _get_resource(self, uid):
'''
Return the URI associated to a particular UID
'''
return URIRef(OLPC['resource/%s' % uid])
def get_uids(self):
'''
Return all the UIDs of the DSObjects stored in that store
'''
query = """
SELECT ?uid WHERE {
?entry <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <%s>.
?entry <%s> ?uid.
}
""" % (OLPC_TERMS['DSObject'], OLPC_TERMS['uid'])
uids = []
sparql = SPARQL(self.store_url)
for result in sparql.execute_select(query):
uids.append(result['uid'])
return uids
def get_object(self, uid, properties=None):
'''
Get a specific object associated to this UID
'''
metadata = {}
query = 'SELECT ?p ?o WHERE { <%s> ?p ?o. }' % self._get_resource(uid)
sparql = SPARQL(self.store_url)
for result in sparql.execute_select(query):
if result['p'].startswith(OLPC_TERMS):
key = result['p'].split(OLPC_TERMS)[1]
if key in _QUERY_INT_KEY:
metadata[key] = int(result['o'])
else:
metadata[key] = result['o']
# HACK: This is expected to be always present
if 'creation_time' not in metadata:
metadata['creation_time'] = int(time.time())
return metadata
def store_object(self, uid, metadata):
'''
Store an object defined by a uid and its associated metadata
'''
metadata['uid'] = uid
# Preprocess the metadata
props = {}
for key, value in metadata.items():
# Hack to support activities that still pass properties named as
# for example title:text.
if ':' in key:
key = key.split(':', 1)[0]
# Re-encode strings
if isinstance(value, unicode):
value = value.encode('utf-8')
elif not isinstance(value, basestring):
value = str(value)
# Save new binding
props[key] = value
# Compose and save the graph
graph = ConjunctiveGraph()
resource = self._get_resource(uid)
graph.add((resource, RDF.type, OLPC_TERMS['DSObject']))
for key, value in props.items():
if isinstance(key, basestring) and isinstance(value, basestring):
key = OLPC_TERMS[key]
try:
value = Literal(value)
graph.add((resource, key, value))
except:
pass
headers = { 'Accept' : '*/*', 'Content-Type': 'application/rdf+xml' }
conn = httplib.HTTPConnection(self.store_url)
conn.request("PUT", "/data/%s" % resource, body=graph.serialize(), headers=headers)
conn.getresponse()
conn.close()
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