Add some documentation and tests for basic graph store interaction.

doc/src/use_cases_transactions.md

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+# Use cases that may involve a transaction
+
+## Add a LDP-RS
+
+1. Add a named graph with some triples
+2. Add metadata about the graph
+
+## Update an LDP-RS
+
+1. Query current resource (named graph)
+2. Apply SPARQL-UPDATE to in-memory graph
+3. Add new named graph with new dataset
+4. Modify (insert and delete triples) metadata in main graph
+
+## (Soft-)Delete a resource
+
+1. Mark resource as deleted in the main graph (set type to tombstone)

lakesuperior/ldp/fcrepo/README.md

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+Implementation of Fedora specs here. Extend LDP classes.

lakesuperior/ldp/lakesuperior/README.md

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+All classes that provide extensions of the standard FCREPO specs go here.

requirements.txt

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+arrow==0.10.0
+Flask==0.12.2
+pytest==3.2.2
+PyYAML==3.12
+rdflib==4.2.2
+requests==2.18.4
+requests-toolbelt==0.8.0
+SPARQLWrapper==1.8.0

tests/initial_tests.py

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+#!/usr/bin/env python3
+
+## Small set of tests to begin with.
+## For testing, import this file:
+##
+## `from tests.initial_tests import *`
+##
+## Then clear the data store with clear() and run
+## individual functions inspecting the dataset at each step.
+
+import pdb
+
+import rdflib
+
+from rdflib.graph import Dataset
+from rdflib.namespace import RDF
+from rdflib.plugins.stores.sparqlstore import SPARQLUpdateStore
+from rdflib.term import URIRef
+
+query_ep = 'http://localhost:3030/lakesuperior-dev/query'
+update_ep = 'http://localhost:3030/lakesuperior-dev/update'
+
+store = SPARQLUpdateStore(queryEndpoint=query_ep, update_endpoint=update_ep,
+        autocommit=False)
+ds = Dataset(store, default_union=True)
+
+
+def query(q):
+    res = ds.query(q)
+    print(res.serialize().decode('utf-8'))
+
+
+def clear():
+    '''Clear triplestore.'''
+    for g in ds.graphs():
+        ds.remove_graph(g)
+    store.commit()
+    print('All graphs removed from store.')
+
+
+def insert(report=False):
+    '''Add a resource.'''
+
+    res1 = ds.graph(URIRef('urn:res:001'))
+    res1.add((URIRef('urn:lake:12873624'), RDF.type, URIRef('http://example.edu#Blah')))
+
+    # Add to default graph. This allows to do something like:
+    # CONSTRUCT {?s ?p ?o}
+    # WHERE {
+    #   ?g1 a <http://example.edu#Resource>  .
+    #   GRAPH ?g1 {
+    #     ?s ?p ?o .
+    #   }
+    # }
+    ds.add((URIRef('urn:res:001'), RDF.type, URIRef('http://example.edu#Resource')))
+    store.commit()
+
+    if report:
+        print('Inserted resource:')
+        query('''
+            SELECT *
+            WHERE {
+              ?g1 a <http://example.edu#Resource>  .
+              GRAPH ?g1 {
+                ?s ?p ?o .
+              }
+            }'''
+        )
+
+
+def update(report=False):
+    '''Update resource and create a historic snapshot.'''
+
+    res2 = ds.graph(URIRef('urn:res:002'))
+    res2.add((URIRef('urn:lake:12873624'), RDF.type, URIRef('http://example.edu#Boo')))
+
+    ds.remove((URIRef('urn:res:001'), RDF.type, URIRef('http://example.edu#Resource')))
+    ds.add((URIRef('urn:res:001'), RDF.type, URIRef('http://example.edu#Snapshot')))
+    ds.add((URIRef('urn:res:002'), RDF.type, URIRef('http://example.edu#Resource')))
+    ds.add((URIRef('urn:res:002'), URIRef('http://example.edu#hasVersion'), URIRef('urn:res:001')))
+    store.commit()
+
+    if report:
+        print('Updated resource:')
+        query('''
+            SELECT *
+            WHERE {
+              ?g1 a <http://example.edu#Resource>  .
+              GRAPH ?g1 {
+                ?s ?p ?o .
+              }
+            }'''
+        )
+        print('Version snapshot:')
+        query('''
+            SELECT *
+            WHERE {
+              ?g1 a <http://example.edu#Snapshot>  .
+              GRAPH ?g1 {
+                ?s ?p ?o .
+              }
+            }'''
+        )
+
+
+def delete(report=False):
+    '''Delete resource and leave a tombstone.'''
+
+    ds.remove((URIRef('urn:res:002'), RDF.type, URIRef('http://example.edu#Resource')))
+    ds.add((URIRef('urn:res:002'), RDF.type, URIRef('http://example.edu#Tombstone')))
+    store.commit()
+
+    if report:
+        print('Deleted resource (tombstone):')
+        query('''
+            SELECT *
+            WHERE {
+              ?g1 a <http://example.edu#Tombstone>  .
+              GRAPH ?g1 {
+                ?s ?p ?o .
+              }
+            }'''
+        )
+
+
+def undelete(report=False):
+    '''Resurrect resource from a tombstone.'''
+
+    ds.remove((URIRef('urn:res:002'), RDF.type, URIRef('http://example.edu#Tombstone')))
+    ds.add((URIRef('urn:res:002'), RDF.type, URIRef('http://example.edu#Resource')))
+    store.commit()
+
+    if report:
+        print('Undeleted resource:')
+        query('''
+            SELECT *
+            WHERE {
+              ?g1 a <http://example.edu#Resource>  .
+              GRAPH ?g1 {
+                ?s ?p ?o .
+              }
+            }'''
+        )
+
+
+def abort_tx(report=False):
+    '''Abort an operation in the middle of a transaction and roll back.'''
+
+    try:
+        res2 = ds.graph(URIRef('urn:res:002'))
+        res2.add((URIRef('urn:lake:12873624'), RDF.type, URIRef('http://example.edu#Werp')))
+        raise RuntimeError('Something awful happened!')
+        store.commit()
+    except RuntimeError as e:
+        print('Exception caught: {}'.format(e))
+        store.rollback()
+
+    if report:
+        print('Failed operation (no updates):')
+        query('''
+            SELECT *
+            WHERE {
+              ?g1 a <http://example.edu#Resource>  .
+              GRAPH ?g1 {
+                ?s ?p ?o .
+              }
+            }'''
+        )
+
+
+def partial_query(report=False):
+    '''Execute a query containing a token that throws an error in the middle.
+
+    The purpose of this is to verify whether the store is truly transactional,
+    i.e. the whole operation in a transaction is rolled back even if some
+    updates have already been processed.'''
+
+    # @TODO
+    pass