def get_target(self, name):
if name is None:
if len(self.theory) == 1:
name = self.theory.keys()[0]
elif len(self.theory) == 0:
raise compile.CongressException("No policies exist.")
else:
raise compile.CongressException(
"Must choose a policy to operate on")
if name not in self.theory:
raise compile.CongressException("Unknown policy " + str(name))
return self.theory[name]
def update_would_cause_errors(self, events):
"""Return a list of compile.CongressException.
Return a list of compile.CongressException if we were
to apply the insert/deletes of policy statements dictated by
EVENTS to the current policy.
"""
self.log(None, "update_would_cause_errors %s", iterstr(events))
errors = []
for event in events:
if not compile.is_datalog(event.formula):
errors.append(
compile.CongressException("Non-formula found: {}".format(
str(event.formula))))
else:
if event.formula.is_atom():
errors.extend(
compile.fact_errors(event.formula, self.theories,
self.name))
else:
errors.extend(
compile.rule_errors(event.formula, self.theories,
self.name))
# Would also check that rules are non-recursive, but that
# is currently being handled by Runtime. The current implementation
# disallows recursion in all theories.
return errors
def update_would_cause_errors(self, events):
"""Return a list of compile.CongressException.
Return a list of compile.CongressException if we were
to apply the events EVENTS to the current policy.
"""
self.log(None, "update_would_cause_errors %s", iterstr(events))
errors = []
for event in events:
if not compile.is_datalog(event.formula):
errors.append(
compile.CongressException("Non-formula found: {}".format(
str(event.formula))))
else:
if event.formula.is_atom():
errors.extend(
compile.fact_errors(event.formula, self.theories,
self.name))
else:
errors.extend(
compile.rule_head_has_no_theory(
event.formula,
permit_head=lambda lit: lit.is_update()))
# Should put this back in place, but there are some
# exceptions that we don't handle right now.
# Would like to mark some tables as only being defined
# for certain bound/free arguments and take that into
# account when doing error checking.
# errors.extend(compile.rule_negation_safety(event.formula))
return errors
def update_obj(self, events):
"""Do the updating.
Checks if applying EVENTS is permitted and if not
returns a list of errors. If it is permitted, it
applies it and then returns a list of changes.
In both cases, the return is a 2-tuple (if-permitted, list).
"""
self.table_log(None, "Updating with %s", iterstr(events))
by_theory = self.group_events_by_target(events)
# check that the updates would not cause an error
errors = []
actual_events = []
for th, th_events in by_theory.items():
th_obj = self.get_target(th)
errors.extend(th_obj.update_would_cause_errors(th_events))
actual_events.extend(th_obj.actual_events(th_events))
# update dependency graph (and undo it if errors)
changes = self.global_dependency_graph.formula_update(events)
if changes:
if self.global_dependency_graph.has_cycle():
# TODO(thinrichs): include path
errors.append(compile.CongressException(
"Rules are recursive"))
self.global_dependency_graph.undo_changes(changes)
if len(errors) > 0:
return (False, errors)
# actually apply the updates
changes = []
for th, th_events in by_theory.items():
changes.extend(self.get_target(th).update(events))
return (True, changes)
def create_policy(self, name, abbr=None, kind=None):
"""Create a new policy and add it to the runtime.
ABBR is a shortened version of NAME that appears in
traces. KIND is the name of the datastructure used to
represent a policy.
"""
if not isinstance(name, basestring):
raise KeyError("Policy name %s must be a string" % name)
if name in self.theory:
raise KeyError("Policy with name %s already exists" % name)
if not isinstance(abbr, basestring):
abbr = name[0:5]
LOG.debug("Creating policy <%s> with abbr <%s> and kind <%s>",
name, abbr, kind)
if kind is None:
kind = NONRECURSIVE_POLICY_TYPE
else:
kind = kind.lower()
if kind is None or kind == NONRECURSIVE_POLICY_TYPE:
PolicyClass = NonrecursiveRuleTheory
elif kind == ACTION_POLICY_TYPE:
PolicyClass = ActionTheory
elif kind == DATABASE_POLICY_TYPE:
PolicyClass = Database
elif kind == MATERIALIZED_POLICY_TYPE:
PolicyClass = MaterializedViewTheory
else:
raise compile.CongressException(
"Unknown kind of policy: %s" % kind)
policy_obj = PolicyClass(name=name, abbr=abbr, theories=self.theory)
policy_obj.set_tracer(self.tracer)
self.theory[name] = policy_obj
return policy_obj
def policy_type(self, name):
"""Return type of policy NAME. Throws KeyError if does not exist."""
policy = self.policy_object(name)
if isinstance(policy, NonrecursiveRuleTheory):
return NONRECURSIVE_POLICY_TYPE
if isinstance(policy, MaterializedViewTheory):
return MATERIALIZED_POLICY_TYPE
if isinstance(policy, ActionTheory):
return ACTION_POLICY_TYPE
if isinstance(policy, Database):
return DATABASE_POLICY_TYPE
raise compile.CongressException("Policy %s has unknown type" % name)
def change_rule(self, parsed_rule, context, insert=True):
policy_name = self.policy_name(context)
if policy_name not in self.engine.theory:
raise KeyError("Policy with ID '%s' does not exist", policy_name)
event = runtime.Event(formula=parsed_rule,
insert=insert,
target=policy_name)
(permitted, changes) = self.engine.process_policy_update([event])
if not permitted:
raise compile.CongressException("Errors: " +
";".join((str(x)
for x in changes)))
return changes
def update_would_cause_errors(self, events):
"""Return a list of compile.CongressException.
Return a list of compile.CongressException if we were
to apply the events EVENTS to the current policy.
"""
self.log(None, "update_would_cause_errors %s", iterstr(events))
errors = []
for event in events:
if not compile.is_atom(event.formula):
errors.append(compile.CongressException(
"Non-atomic formula is not permitted: {}".format(
str(event.formula))))
else:
errors.extend(compile.fact_errors(
event.formula, self.theories, self.name))
return errors
def project(self, sequence, policy_theory, action_theory):
"""Apply the list of updates SEQUENCE.
Apply the list of updates SEQUENCE, where actions are described
in ACTION_THEORY. Return an update sequence that will undo the
projection.
SEQUENCE can include atom insert/deletes, rule insert/deletes,
and action invocations. Projecting an action only
simulates that action's invocation using the action's description;
the results are therefore only an approximation of executing
actions directly. Elements of SEQUENCE are just formulas
applied to the given THEORY. They are NOT Event()s.
SEQUENCE is really a program in a mini-programming
language--enabling results of one action to be passed to another.
Hence, even ignoring actions, this functionality cannot be achieved
by simply inserting/deleting.
"""
actth = self.theory[action_theory]
policyth = self.theory[policy_theory]
# apply changes to the state
newth = NonrecursiveRuleTheory(abbr="Temp")
newth.tracer.trace('*')
actth.includes.append(newth)
# TODO(thinrichs): turn 'includes' into an object that guarantees
# there are no cycles through inclusion. Otherwise we get
# infinite loops
if actth is not policyth:
actth.includes.append(policyth)
actions = self.get_action_names(action_theory)
self.table_log(None, "Actions: %s", iterstr(actions))
undos = [] # a list of updates that will undo SEQUENCE
self.table_log(None, "Project: %s", sequence)
last_results = []
for formula in sequence:
self.table_log(None, "** Updating with %s", formula)
self.table_log(None, "Actions: %s", iterstr(actions))
self.table_log(None, "Last_results: %s", iterstr(last_results))
tablename = formula.tablename()
if tablename not in actions:
if not formula.is_update():
raise compile.CongressException(
"Sequence contained non-action, non-update: " +
str(formula))
updates = [formula]
else:
self.table_log(tablename, "Projecting %s", formula)
# define extension of current Actions theory
if formula.is_atom():
assert formula.is_ground(), (
"Projection atomic updates must be ground")
assert not formula.is_negated(), (
"Projection atomic updates must be positive")
newth.define([formula])
else:
# instantiate action using prior results
newth.define(last_results)
self.table_log(tablename, "newth (with prior results) %s",
iterstr(newth.content()))
bindings = actth.top_down_evaluation(
formula.variables(), formula.body, find_all=False)
if len(bindings) == 0:
continue
grounds = formula.plug_heads(bindings[0])
grounds = [act for act in grounds if act.is_ground()]
assert all(not lit.is_negated() for lit in grounds)
newth.define(grounds)
self.table_log(tablename,
"newth contents (after action insertion): %s",
iterstr(newth.content()))
# self.table_log(tablename, "action contents: %s",
# iterstr(actth.content()))
# self.table_log(tablename, "action.includes[1] contents: %s",
# iterstr(actth.includes[1].content()))
# self.table_log(tablename, "newth contents: %s",
# iterstr(newth.content()))
# compute updates caused by action
updates = actth.consequences(compile.is_update)
updates = self.resolve_conflicts(updates)
updates = unify.skolemize(updates)
self.table_log(tablename, "Computed updates: %s",
iterstr(updates))
# compute results for next time
for update in updates:
newth.insert(update)
last_results = actth.consequences(compile.is_result)
last_results = set([atom for atom in last_results
if atom.is_ground()])
# apply updates
for update in updates:
undo = self.project_updates(update, policy_theory)
if undo is not None:
undos.append(undo)
undos.reverse()
if actth is not policyth:
actth.includes.remove(policyth)
actth.includes.remove(newth)
return undos
