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+import arrow
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+
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+from uuid import uuid4
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+
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+from rdflib import Dataset, Graph
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+from rdflib.namespace import FOAF, RDF, XSD
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+from rdflib.plugins.sparql import prepareQuery
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+from rdflib.plugins.stores.sparqlstore import SPARQLUpdateStore
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+from rdflib.term import URIRef, Literal
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+
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+from lakesuperior.core.namespaces import ns_collection as nsc
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+from lakesuperior.core.namespaces import ns_mgr as nsm
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+from lakesuperior.store_layouts.rdf.base_rdf_layout import BaseRdfLayout
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+
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+
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+class FullProvenanceLayout(BaseRdfLayout):
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+ '''This is an implementation of the
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+ [graph-per-resource pattern](http://patterns.dataincubator.org/book/graph-per-resource.html)
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+ which stores each LDP resource in a separate graph, with a "main" graph
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+ to keep track of resource metadata.
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+ '''
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+
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+ DEFAULT_AGENT_URI = nsc['lake'].defaultAgent
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+ MAIN_GRAPH_URI = nsc['fcg'].meta
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+
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+
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+ ## MAGIC METHODS ##
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+
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+ def __init__(self):
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+ self.main_graph = self.ds.graph(self.MAIN_GRAPH_URI)
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+
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+
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+ ## PUBLIC METHODS ##
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+
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+ def ask_rsrc_exists(self, uuid):
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+ '''Return whether the resource exists.
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+
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+ @param uuid Resource UUID.
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+
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+ @retrn boolean
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+ '''
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+ res = self.ds.graph(self.UNION_GRAPH_URI).resource(nsc['fcres'][uuid])
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+
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+ return len(res) > 0
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+
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+
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+ def get_rsrc(self, uuid):
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+ '''Get a resource graph.
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+ '''
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+ res = self.ds.graph(self.UNION_GRAPH_URI).query(
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+ 'CONSTRUCT WHERE { ?s ?p ?o }',
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+ initBindings={'s' : nsc['fcres'][uuid]}
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+ )
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+
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+ return self.globalize_graph(res.graph)
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+
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+
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+ def put_rsrc(self, uuid, data, format='text/turtle', base_types=None,
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+ agent=None):
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+ '''Create a resource graph.
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+
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+ If the resource UUID exists already, it is either overwritten or a
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+ version snapshot is created, depending on the parameters.
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+ '''
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+ if agent is None:
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+ agent = self.DEFAULT_AGENT_URI
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+
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+ res_urn = nsc['fcres'][uuid]
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+
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+ # If there is a statement by this agent about this resource, replace
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+ # its contents.
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+ if self._get_res_stmt_by_agent(res_urn, agent):
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+ pass # @TODO
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+
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+
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+ # If the graph URI does not exist, create a new resource.
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+ else:
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+ # Create a new UUID for the statement set.
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+ stmset_uri = nsc['stmset'][str(uuid4())]
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+
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+ # Create a temp graph to store the loaded data. For some reason,
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+ # loading directly into the stored graph throws an assertion error.
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+ tmp_g = Graph()
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+ tmp_g.parse(data=data.decode('utf-8'), format=format,
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+ publicID=str(res_urn))
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+
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+ # Create the graph and add the data.
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+ g = self.ds.graph(stmset_uri)
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+ g += tmp_g
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+
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+ # Add metadata.
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+ ts = arrow.utcnow()
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+ main_graph = self.ds.graph(self.MAIN_GRAPH_URI)
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+
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+ main_graph.add((stmset_uri, FOAF.primaryTopic, res_urn))
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+ main_graph.add((stmset_uri, RDF.type, nsc['prov'].Entity))
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+ main_graph.add(
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+ (stmset_uri, nsc['prov'].generatedAtTime,
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+ Literal(ts, datatype=XSD.dateTime)))
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+ main_graph.add(
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+ (stmset_uri, nsc['prov'].wasAttributedTo, agent))
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+
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+
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+ #self.create_version(res_urn)
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+
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+ if base_types:
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+ for type_uri in self.base_types:
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+ main_graph.add((stmset_uri, RDF.type, type_uri))
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+
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+ # @TODO Create containment triples
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+
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+ self.conn.store.commit()
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+
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+
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+
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+ #def create_version(self, res_urn):
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+ # '''Swap out previous version if existing, and create new version
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+ # dependency.'''
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+ # main_graph = ds.graph(URIRef('urn:lake:' + self.MAIN_GRAPH_NAME))
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+ # prv_res_urn = self.select_current_graph_for_res(res_urn)
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+
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+ # if prv_res_urn:
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+ # main_graph.remove((prv_res_urn, RDF.type, nsc['lake'].Resource))
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+ # main_graph.add((prv_res_urn, RDF.type, nsc['lake'].Snapshot))
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+
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+ # main_graph.add((res_urn, RDF.type, nsc['lake'].Resource))
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+ # main_graph.add((res_urn, nsc['lake'].previousVersion, prv_res_urn))
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+
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+
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+ #def select_current_graph_for_res(self, urn):
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+ # '''Select the current graph URI for a given resource.'''
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+ # qry = '''
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+ # SELECT ?g {
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+ # GRAPH ?mg { ?g a ?gt . }
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+ # GRAPH ?g { ?s ?p ?o . }
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+ # }
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+ # LIMIT 1
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+ # '''
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+ # rsp = self.ds.query(qry, initBindings={
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+ # 'mg' : URIRef('urn:lake:' + self.MAIN_GRAPH_NAME),
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+ # 'gt' : RESOURCE_TYPE_URI,
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+ # 's' : urn
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+ # })
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+
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+ # return list(rsp[0][0])
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+
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+
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+ def _ask_res_stmt_by_agent_exists(self, res_urn, agent):
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+ '''Ask if any statements have been made by a certain agent about a
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+ certain resource.
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+
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+ @param rdflib.term.URIRef res_urn Resource URN.
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+ @param rdflib.term.URIRef agent Agent URI.
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+
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+ @return boolean
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+ '''
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+ return self.query('''
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+ ASK {
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+ GRAPH ?mg {
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+ ?g prov:wasAttributedTo ?a .
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+ }
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+ GRAPH ?g {
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+ ?s ?p ?o .
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+ }
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+ }
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+ ''', initBindings={
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+ 'a' : agent,
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+ 's' : res_urn,
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+ })
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+
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Stefano Cossu