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'''
Created on Apr 11, 2011
@author: cgueret
'''
import logging
import httplib
import time
from rdflib import ConjunctiveGraph, RDF, URIRef, Namespace, Literal
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 MetadataStore(object):
'''
Store metadata into the triple store using HTTP calls.
'''
def __init__(self):
self._url = '127.0.0.1:8080'
def store(self, uid, metadata):
logging.debug('[MDS] store ' + uid + ' ' + str(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
# Save it
logging.debug('[MDS] save > %s' % graph.serialize())
headers = { 'Accept' : '*/*', 'Content-Type': 'application/rdf+xml' }
conn = httplib.HTTPConnection(self._url)
conn.request("PUT", "/data/%s" % resource, body=graph.serialize(), headers=headers)
conn.getresponse()
conn.close()
def retrieve(self, uid, properties=None):
logging.debug('[MDS] retrieve %r' % uid)
props = {}
query = 'SELECT ?p ?o WHERE { <%s> ?p ?o. }' % self._get_resource(uid)
sparql = SPARQL()
for result in sparql.execute_select(query):
logging.debug('[MDS] result %r' % result)
print result
if result['p'].startswith(OLPC_TERMS):
key=result['p'].split(OLPC_TERMS)[1]
if key in _QUERY_INT_KEY:
props[key] = int(result['o'])
else:
props[key] = result['o']
# HACK: This is expected to be always present
if 'creation_time' not in props:
props['creation_time'] = int(time.time())
return props
def delete(self, uid):
print '[MDS] delete'
pass
def get_property(self, uid, key):
print '[MDS] get'
pass
def set_property(self, uid, key, value):
print '[MDS] set'
pass
def _get_resource(self, uid):
return URIRef(OLPC['resource/%s' % uid])
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