cubicweb/schema.py
changeset 11057 0b59724cb3f2
parent 11039 6424a2e112f5
child 11151 4259c55df3e7
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/cubicweb/schema.py	Sat Jan 16 13:48:51 2016 +0100
@@ -0,0 +1,1458 @@
+# copyright 2003-2014 LOGILAB S.A. (Paris, FRANCE), all rights reserved.
+# contact http://www.logilab.fr/ -- mailto:contact@logilab.fr
+#
+# This file is part of CubicWeb.
+#
+# CubicWeb is free software: you can redistribute it and/or modify it under the
+# terms of the GNU Lesser General Public License as published by the Free
+# Software Foundation, either version 2.1 of the License, or (at your option)
+# any later version.
+#
+# CubicWeb is distributed in the hope that it will be useful, but WITHOUT
+# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+# FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public License for more
+# details.
+#
+# You should have received a copy of the GNU Lesser General Public License along
+# with CubicWeb.  If not, see <http://www.gnu.org/licenses/>.
+"""classes to define schemas for CubicWeb"""
+from __future__ import print_function
+
+__docformat__ = "restructuredtext en"
+
+import re
+from os.path import join, basename
+from logging import getLogger
+from warnings import warn
+
+from six import PY2, text_type, string_types, add_metaclass
+from six.moves import range
+
+from logilab.common import tempattr
+from logilab.common.decorators import cached, clear_cache, monkeypatch, cachedproperty
+from logilab.common.logging_ext import set_log_methods
+from logilab.common.deprecation import deprecated, class_moved, moved
+from logilab.common.textutils import splitstrip
+from logilab.common.graph import get_cycles
+
+import yams
+from yams import BadSchemaDefinition, buildobjs as ybo
+from yams.schema import Schema, ERSchema, EntitySchema, RelationSchema, \
+     RelationDefinitionSchema, PermissionMixIn, role_name
+from yams.constraints import (BaseConstraint, FormatConstraint, BoundaryConstraint,
+                              IntervalBoundConstraint, StaticVocabularyConstraint)
+from yams.reader import (CONSTRAINTS, PyFileReader, SchemaLoader,
+                         cleanup_sys_modules, fill_schema_from_namespace)
+
+from rql import parse, nodes, RQLSyntaxError, TypeResolverException
+from rql.analyze import ETypeResolver
+
+import cubicweb
+from cubicweb import ETYPE_NAME_MAP, ValidationError, Unauthorized, _
+
+try:
+    from cubicweb import server
+except ImportError:
+    # We need to lookup DEBUG from there,
+    # however a pure dbapi client may not have it.
+    class server(object): pass
+    server.DEBUG = False
+
+
+PURE_VIRTUAL_RTYPES = set(('identity', 'has_text',))
+VIRTUAL_RTYPES = set(('eid', 'identity', 'has_text',))
+
+# set of meta-relations available for every entity types
+META_RTYPES = set((
+    'owned_by', 'created_by', 'is', 'is_instance_of', 'identity',
+    'eid', 'creation_date', 'cw_source', 'modification_date', 'has_text', 'cwuri',
+    ))
+WORKFLOW_RTYPES = set(('custom_workflow', 'in_state', 'wf_info_for'))
+WORKFLOW_DEF_RTYPES = set(('workflow_of', 'state_of', 'transition_of',
+                           'initial_state', 'default_workflow',
+                           'allowed_transition', 'destination_state',
+                           'from_state', 'to_state', 'condition',
+                           'subworkflow', 'subworkflow_state', 'subworkflow_exit',
+                           'by_transition',
+                           ))
+SYSTEM_RTYPES = set(('in_group', 'require_group',
+                     # cwproperty
+                     'for_user',
+                     'cw_schema', 'cw_import_of', 'cw_for_source',
+                     'cw_host_config_of',
+                     )) | WORKFLOW_RTYPES
+NO_I18NCONTEXT = META_RTYPES | WORKFLOW_RTYPES
+
+SKIP_COMPOSITE_RELS = [('cw_source', 'subject')]
+
+# set of entity and relation types used to build the schema
+SCHEMA_TYPES = set((
+    'CWEType', 'CWRType', 'CWComputedRType', 'CWAttribute', 'CWRelation',
+    'CWConstraint', 'CWConstraintType', 'CWUniqueTogetherConstraint',
+    'RQLExpression',
+    'specializes',
+    'relation_type', 'from_entity', 'to_entity',
+    'constrained_by', 'cstrtype',
+    'constraint_of', 'relations',
+    'read_permission', 'add_permission',
+    'delete_permission', 'update_permission',
+    ))
+
+WORKFLOW_TYPES = set(('Transition', 'State', 'TrInfo', 'Workflow',
+                      'WorkflowTransition', 'BaseTransition',
+                      'SubWorkflowExitPoint'))
+
+INTERNAL_TYPES = set(('CWProperty', 'CWCache', 'ExternalUri', 'CWDataImport',
+                      'CWSource', 'CWSourceHostConfig', 'CWSourceSchemaConfig'))
+
+UNIQUE_CONSTRAINTS = ('SizeConstraint', 'FormatConstraint',
+                      'StaticVocabularyConstraint',
+                      'RQLVocabularyConstraint')
+
+_LOGGER = getLogger('cubicweb.schemaloader')
+
+# entity and relation schema created from serialized schema have an eid
+ybo.ETYPE_PROPERTIES += ('eid',)
+ybo.RTYPE_PROPERTIES += ('eid',)
+
+def build_schema_from_namespace(items):
+    schema = CubicWebSchema('noname')
+    fill_schema_from_namespace(schema, items, register_base_types=False)
+    return schema
+
+# Bases for manipulating RQL in schema #########################################
+
+def guess_rrqlexpr_mainvars(expression):
+    defined = set(split_expression(expression))
+    mainvars = set()
+    if 'S' in defined:
+        mainvars.add('S')
+    if 'O' in defined:
+        mainvars.add('O')
+    if 'U' in defined:
+        mainvars.add('U')
+    if not mainvars:
+        raise BadSchemaDefinition('unable to guess selection variables in %r'
+                                  % expression)
+    return mainvars
+
+def split_expression(rqlstring):
+    for expr in rqlstring.split(','):
+        for noparen1 in expr.split('('):
+            for noparen2 in noparen1.split(')'):
+                for word in noparen2.split():
+                    yield word
+
+def normalize_expression(rqlstring):
+    """normalize an rql expression to ease schema synchronization (avoid
+    suppressing and reinserting an expression if only a space has been
+    added/removed for instance)
+    """
+    union = parse(u'Any 1 WHERE %s' % rqlstring).as_string()
+    if PY2 and isinstance(union, str):
+        union = union.decode('utf-8')
+    return union.split(' WHERE ', 1)[1]
+
+
+def _check_valid_formula(rdef, formula_rqlst):
+    """Check the formula is a valid RQL query with some restriction (no union,
+    single selected node, etc.), raise BadSchemaDefinition if not
+    """
+    if len(formula_rqlst.children) != 1:
+        raise BadSchemaDefinition('computed attribute %(attr)s on %(etype)s: '
+                                  'can not use UNION in formula %(form)r' %
+                                  {'attr' : rdef.rtype,
+                                   'etype' : rdef.subject.type,
+                                   'form' : rdef.formula})
+    select = formula_rqlst.children[0]
+    if len(select.selection) != 1:
+        raise BadSchemaDefinition('computed attribute %(attr)s on %(etype)s: '
+                                  'can only select one term in formula %(form)r' %
+                                  {'attr' : rdef.rtype,
+                                   'etype' : rdef.subject.type,
+                                   'form' : rdef.formula})
+    term = select.selection[0]
+    types = set(term.get_type(sol) for sol in select.solutions)
+    if len(types) != 1:
+        raise BadSchemaDefinition('computed attribute %(attr)s on %(etype)s: '
+                                  'multiple possible types (%(types)s) for formula %(form)r' %
+                                  {'attr' : rdef.rtype,
+                                   'etype' : rdef.subject.type,
+                                   'types' : list(types),
+                                   'form' : rdef.formula})
+    computed_type = types.pop()
+    expected_type = rdef.object.type
+    if computed_type != expected_type:
+        raise BadSchemaDefinition('computed attribute %(attr)s on %(etype)s: '
+                                  'computed attribute type (%(comp_type)s) mismatch with '
+                                  'specified type (%(attr_type)s)' %
+                                  {'attr' : rdef.rtype,
+                                   'etype' : rdef.subject.type,
+                                   'comp_type' : computed_type,
+                                   'attr_type' : expected_type})
+
+
+class RQLExpression(object):
+    """Base class for RQL expression used in schema (constraints and
+    permissions)
+    """
+    # these are overridden by set_log_methods below
+    # only defining here to prevent pylint from complaining
+    info = warning = error = critical = exception = debug = lambda msg,*a,**kw: None
+    # to be defined in concrete classes
+    rqlst = None
+    predefined_variables = None
+    full_rql = None
+
+    def __init__(self, expression, mainvars, eid):
+        """
+        :type mainvars: sequence of RQL variables' names. Can be provided as a
+                        comma separated string.
+        :param mainvars: names of the variables being selected.
+
+        """
+        self.eid = eid # eid of the entity representing this rql expression
+        assert mainvars, 'bad mainvars %s' % mainvars
+        if isinstance(mainvars, string_types):
+            mainvars = set(splitstrip(mainvars))
+        elif not isinstance(mainvars, set):
+            mainvars = set(mainvars)
+        self.mainvars = mainvars
+        self.expression = normalize_expression(expression)
+        try:
+            self.full_rql = self.rqlst.as_string()
+        except RQLSyntaxError:
+            raise RQLSyntaxError(expression)
+        for mainvar in mainvars:
+            # if variable is predefined, an extra reference is inserted
+            # automatically (`VAR eid %(v)s`)
+            if mainvar in self.predefined_variables:
+                min_refs = 3
+            else:
+                min_refs = 2
+            if len(self.rqlst.defined_vars[mainvar].references()) < min_refs:
+                _LOGGER.warn('You did not use the %s variable in your RQL '
+                             'expression %s', mainvar, self)
+        # syntax tree used by read security (inserted in queries when necessary)
+        self.snippet_rqlst = parse(self.minimal_rql, print_errors=False).children[0]
+        # graph of links between variables, used by rql rewriter
+        self.vargraph = vargraph(self.rqlst)
+        # useful for some instrumentation, e.g. localperms permcheck command
+        self.package = ybo.PACKAGE
+
+    def __str__(self):
+        return self.full_rql
+    def __repr__(self):
+        return '%s(%s)' % (self.__class__.__name__, self.full_rql)
+
+    def __lt__(self, other):
+        if hasattr(other, 'expression'):
+            return self.expression < other.expression
+        return True
+
+    def __eq__(self, other):
+        if hasattr(other, 'expression'):
+            return self.expression == other.expression
+        return False
+
+    def __ne__(self, other):
+        return not (self == other)
+
+    def __hash__(self):
+        return hash(self.expression)
+
+    def __deepcopy__(self, memo):
+        return self.__class__(self.expression, self.mainvars)
+    def __getstate__(self):
+        return (self.expression, self.mainvars)
+    def __setstate__(self, state):
+        self.__init__(*state)
+
+    @cachedproperty
+    def rqlst(self):
+        select = parse(self.minimal_rql, print_errors=False).children[0]
+        defined = set(split_expression(self.expression))
+        for varname in self.predefined_variables:
+            if varname in defined:
+                select.add_eid_restriction(select.get_variable(varname), varname.lower(), 'Substitute')
+        return select
+
+    # permission rql expression specific stuff #################################
+
+    @cached
+    def transform_has_permission(self):
+        found = None
+        rqlst = self.rqlst
+        for var in rqlst.defined_vars.values():
+            for varref in var.references():
+                rel = varref.relation()
+                if rel is None:
+                    continue
+                try:
+                    prefix, action, suffix = rel.r_type.split('_')
+                except ValueError:
+                    continue
+                if prefix != 'has' or suffix != 'permission' or \
+                       not action in ('add', 'delete', 'update', 'read'):
+                    continue
+                if found is None:
+                    found = []
+                    rqlst.save_state()
+                assert rel.children[0].name == 'U'
+                objvar = rel.children[1].children[0].variable
+                rqlst.remove_node(rel)
+                selected = [v.name for v in rqlst.get_selected_variables()]
+                if objvar.name not in selected:
+                    colindex = len(selected)
+                    rqlst.add_selected(objvar)
+                else:
+                    colindex = selected.index(objvar.name)
+                found.append((action, colindex))
+                # remove U eid %(u)s if U is not used in any other relation
+                uvrefs = rqlst.defined_vars['U'].references()
+                if len(uvrefs) == 1:
+                    rqlst.remove_node(uvrefs[0].relation())
+        if found is not None:
+            rql = rqlst.as_string()
+            if len(rqlst.selection) == 1 and isinstance(rqlst.where, nodes.Relation):
+                # only "Any X WHERE X eid %(x)s" remaining, no need to execute the rql
+                keyarg = rqlst.selection[0].name.lower()
+            else:
+                keyarg = None
+            rqlst.recover()
+            return rql, found, keyarg
+        return rqlst.as_string(), None, None
+
+    def _check(self, _cw, **kwargs):
+        """return True if the rql expression is matching the given relation
+        between fromeid and toeid
+
+        _cw may be a request or a server side transaction
+        """
+        creating = kwargs.get('creating')
+        if not creating and self.eid is not None:
+            key = (self.eid, tuple(sorted(kwargs.items())))
+            try:
+                return _cw.local_perm_cache[key]
+            except KeyError:
+                pass
+        rql, has_perm_defs, keyarg = self.transform_has_permission()
+        # when creating an entity, expression related to X satisfied
+        if creating and 'X' in self.rqlst.defined_vars:
+            return True
+        if keyarg is None:
+            kwargs.setdefault('u', _cw.user.eid)
+            try:
+                rset = _cw.execute(rql, kwargs, build_descr=True)
+            except NotImplementedError:
+                self.critical('cant check rql expression, unsupported rql %s', rql)
+                if self.eid is not None:
+                    _cw.local_perm_cache[key] = False
+                return False
+            except TypeResolverException as ex:
+                # some expression may not be resolvable with current kwargs
+                # (type conflict)
+                self.warning('%s: %s', rql, str(ex))
+                if self.eid is not None:
+                    _cw.local_perm_cache[key] = False
+                return False
+            except Unauthorized as ex:
+                self.debug('unauthorized %s: %s', rql, str(ex))
+                if self.eid is not None:
+                    _cw.local_perm_cache[key] = False
+                return False
+        else:
+            rset = _cw.eid_rset(kwargs[keyarg])
+        # if no special has_*_permission relation in the rql expression, just
+        # check the result set contains something
+        if has_perm_defs is None:
+            if rset:
+                if self.eid is not None:
+                    _cw.local_perm_cache[key] = True
+                return True
+        elif rset:
+            # check every special has_*_permission relation is satisfied
+            get_eschema = _cw.vreg.schema.eschema
+            try:
+                for eaction, col in has_perm_defs:
+                    for i in range(len(rset)):
+                        eschema = get_eschema(rset.description[i][col])
+                        eschema.check_perm(_cw, eaction, eid=rset[i][col])
+                if self.eid is not None:
+                    _cw.local_perm_cache[key] = True
+                return True
+            except Unauthorized:
+                pass
+        if self.eid is not None:
+            _cw.local_perm_cache[key] = False
+        return False
+
+    @property
+    def minimal_rql(self):
+        return 'Any %s WHERE %s' % (','.join(sorted(self.mainvars)),
+                                    self.expression)
+
+
+
+# rql expressions for use in permission definition #############################
+
+class ERQLExpression(RQLExpression):
+    predefined_variables = 'XU'
+
+    def __init__(self, expression, mainvars=None, eid=None):
+        RQLExpression.__init__(self, expression, mainvars or 'X', eid)
+
+    def check(self, _cw, eid=None, creating=False, **kwargs):
+        if 'X' in self.rqlst.defined_vars:
+            if eid is None:
+                if creating:
+                    return self._check(_cw, creating=True, **kwargs)
+                return False
+            assert creating == False
+            return self._check(_cw, x=eid, **kwargs)
+        return self._check(_cw, **kwargs)
+
+
+class CubicWebRelationDefinitionSchema(RelationDefinitionSchema):
+    def constraint_by_eid(self, eid):
+        for cstr in self.constraints:
+            if cstr.eid == eid:
+                return cstr
+        raise ValueError('No constraint with eid %d' % eid)
+
+    def rql_expression(self, expression, mainvars=None, eid=None):
+        """rql expression factory"""
+        if self.rtype.final:
+            return ERQLExpression(expression, mainvars, eid)
+        return RRQLExpression(expression, mainvars, eid)
+
+    def check_permission_definitions(self):
+        super(CubicWebRelationDefinitionSchema, self).check_permission_definitions()
+        schema = self.subject.schema
+        for action, groups in self.permissions.items():
+            for group_or_rqlexpr in groups:
+                if action == 'read' and \
+                       isinstance(group_or_rqlexpr, RQLExpression):
+                    msg = "can't use rql expression for read permission of %s"
+                    raise BadSchemaDefinition(msg % self)
+                if self.final and isinstance(group_or_rqlexpr, RRQLExpression):
+                    msg = "can't use RRQLExpression on %s, use an ERQLExpression"
+                    raise BadSchemaDefinition(msg % self)
+                if not self.final and isinstance(group_or_rqlexpr, ERQLExpression):
+                    msg = "can't use ERQLExpression on %s, use a RRQLExpression"
+                    raise BadSchemaDefinition(msg % self)
+
+def vargraph(rqlst):
+    """ builds an adjacency graph of variables from the rql syntax tree, e.g:
+    Any O,S WHERE T subworkflow_exit S, T subworkflow WF, O state_of WF
+    => {'WF': ['O', 'T'], 'S': ['T'], 'T': ['WF', 'S'], 'O': ['WF']}
+    """
+    vargraph = {}
+    for relation in rqlst.get_nodes(nodes.Relation):
+        try:
+            rhsvarname = relation.children[1].children[0].variable.name
+            lhsvarname = relation.children[0].name
+        except AttributeError:
+            pass
+        else:
+            vargraph.setdefault(lhsvarname, []).append(rhsvarname)
+            vargraph.setdefault(rhsvarname, []).append(lhsvarname)
+            #vargraph[(lhsvarname, rhsvarname)] = relation.r_type
+    return vargraph
+
+
+class GeneratedConstraint(object):
+    def __init__(self, rqlst, mainvars):
+        self.snippet_rqlst = rqlst
+        self.mainvars = mainvars
+        self.vargraph = vargraph(rqlst)
+
+
+class RRQLExpression(RQLExpression):
+    predefined_variables = 'SOU'
+
+    def __init__(self, expression, mainvars=None, eid=None):
+        if mainvars is None:
+            mainvars = guess_rrqlexpr_mainvars(expression)
+        RQLExpression.__init__(self, expression, mainvars, eid)
+
+    def check(self, _cw, fromeid=None, toeid=None):
+        kwargs = {}
+        if 'S' in self.rqlst.defined_vars:
+            if fromeid is None:
+                return False
+            kwargs['s'] = fromeid
+        if 'O' in self.rqlst.defined_vars:
+            if toeid is None:
+                return False
+            kwargs['o'] = toeid
+        return self._check(_cw, **kwargs)
+
+
+# In yams, default 'update' perm for attributes granted to managers and owners.
+# Within cw, we want to default to users who may edit the entity holding the
+# attribute.
+# These default permissions won't be checked by the security hooks:
+# since they delegate checking to the entity, we can skip actual checks.
+ybo.DEFAULT_ATTRPERMS['update'] = ('managers', ERQLExpression('U has_update_permission X'))
+ybo.DEFAULT_ATTRPERMS['add'] = ('managers', ERQLExpression('U has_add_permission X'))
+
+# we don't want 'add' or 'delete' permissions on computed relation types
+# (they're hardcoded to '()' on computed relation definitions)
+if 'add' in yams.DEFAULT_COMPUTED_RELPERMS:
+    del yams.DEFAULT_COMPUTED_RELPERMS['add']
+if 'delete' in yams.DEFAULT_COMPUTED_RELPERMS:
+    del yams.DEFAULT_COMPUTED_RELPERMS['delete']
+
+
+PUB_SYSTEM_ENTITY_PERMS = {
+    'read':   ('managers', 'users', 'guests',),
+    'add':    ('managers',),
+    'delete': ('managers',),
+    'update': ('managers',),
+    }
+PUB_SYSTEM_REL_PERMS = {
+    'read':   ('managers', 'users', 'guests',),
+    'add':    ('managers',),
+    'delete': ('managers',),
+    }
+PUB_SYSTEM_ATTR_PERMS = {
+    'read':   ('managers', 'users', 'guests',),
+    'add': ('managers',),
+    'update': ('managers',),
+    }
+RO_REL_PERMS = {
+    'read':   ('managers', 'users', 'guests',),
+    'add':    (),
+    'delete': (),
+    }
+RO_ATTR_PERMS = {
+    'read':   ('managers', 'users', 'guests',),
+    'add': ybo.DEFAULT_ATTRPERMS['add'],
+    'update': (),
+    }
+
+# XXX same algorithm as in reorder_cubes and probably other place,
+# may probably extract a generic function
+def order_eschemas(eschemas):
+    """return entity schemas ordered such that entity types which specializes an
+    other one appears after that one
+    """
+    graph = {}
+    for eschema in eschemas:
+        if eschema.specializes():
+            graph[eschema] = set((eschema.specializes(),))
+        else:
+            graph[eschema] = set()
+    cycles = get_cycles(graph)
+    if cycles:
+        cycles = '\n'.join(' -> '.join(cycle) for cycle in cycles)
+        raise Exception('cycles in entity schema specialization: %s'
+                        % cycles)
+    eschemas = []
+    while graph:
+        # sorted to get predictable results
+        for eschema, deps in sorted(graph.items()):
+            if not deps:
+                eschemas.append(eschema)
+                del graph[eschema]
+                for deps in graph.values():
+                    try:
+                        deps.remove(eschema)
+                    except KeyError:
+                        continue
+    return eschemas
+
+def bw_normalize_etype(etype):
+    if etype in ETYPE_NAME_MAP:
+        msg = '%s has been renamed to %s, please update your code' % (
+            etype, ETYPE_NAME_MAP[etype])
+        warn(msg, DeprecationWarning, stacklevel=4)
+        etype = ETYPE_NAME_MAP[etype]
+    return etype
+
+def display_name(req, key, form='', context=None):
+    """return a internationalized string for the key (schema entity or relation
+    name) in a given form
+    """
+    assert form in ('', 'plural', 'subject', 'object')
+    if form == 'subject':
+        form = ''
+    if form:
+        key = key + '_' + form
+    # ensure unicode
+    if context is not None:
+        return text_type(req.pgettext(context, key))
+    else:
+        return text_type(req._(key))
+
+
+# Schema objects definition ###################################################
+
+def ERSchema_display_name(self, req, form='', context=None):
+    """return a internationalized string for the entity/relation type name in
+    a given form
+    """
+    return display_name(req, self.type, form, context)
+ERSchema.display_name = ERSchema_display_name
+
+@cached
+def get_groups(self, action):
+    """return the groups authorized to perform <action> on entities of
+    this type
+
+    :type action: str
+    :param action: the name of a permission
+
+    :rtype: tuple
+    :return: names of the groups with the given permission
+    """
+    assert action in self.ACTIONS, action
+    #assert action in self._groups, '%s %s' % (self, action)
+    try:
+        return frozenset(g for g in self.permissions[action] if isinstance(g, string_types))
+    except KeyError:
+        return ()
+PermissionMixIn.get_groups = get_groups
+
+@cached
+def get_rqlexprs(self, action):
+    """return the rql expressions representing queries to check the user is allowed
+    to perform <action> on entities of this type
+
+    :type action: str
+    :param action: the name of a permission
+
+    :rtype: tuple
+    :return: the rql expressions with the given permission
+    """
+    assert action in self.ACTIONS, action
+    #assert action in self._rqlexprs, '%s %s' % (self, action)
+    try:
+        return tuple(g for g in self.permissions[action] if not isinstance(g, string_types))
+    except KeyError:
+        return ()
+PermissionMixIn.get_rqlexprs = get_rqlexprs
+
+orig_set_action_permissions = PermissionMixIn.set_action_permissions
+def set_action_permissions(self, action, permissions):
+    """set the groups and rql expressions allowing to perform <action> on
+    entities of this type
+
+    :type action: str
+    :param action: the name of a permission
+
+    :type permissions: tuple
+    :param permissions: the groups and rql expressions allowing the given action
+    """
+    orig_set_action_permissions(self, action, tuple(permissions))
+    clear_cache(self, 'get_rqlexprs')
+    clear_cache(self, 'get_groups')
+PermissionMixIn.set_action_permissions = set_action_permissions
+
+def has_local_role(self, action):
+    """return true if the action *may* be granted locally (i.e. either rql
+    expressions or the owners group are used in security definition)
+
+    XXX this method is only there since we don't know well how to deal with
+    'add' action checking. Also find a better name would be nice.
+    """
+    assert action in self.ACTIONS, action
+    if self.get_rqlexprs(action):
+        return True
+    if action in ('update', 'delete'):
+        return 'owners' in self.get_groups(action)
+    return False
+PermissionMixIn.has_local_role = has_local_role
+
+def may_have_permission(self, action, req):
+    if action != 'read' and not (self.has_local_role('read') or
+                                 self.has_perm(req, 'read')):
+        return False
+    return self.has_local_role(action) or self.has_perm(req, action)
+PermissionMixIn.may_have_permission = may_have_permission
+
+def has_perm(self, _cw, action, **kwargs):
+    """return true if the action is granted globally or locally"""
+    try:
+        self.check_perm(_cw, action, **kwargs)
+        return True
+    except Unauthorized:
+        return False
+PermissionMixIn.has_perm = has_perm
+
+
+def check_perm(self, _cw, action, **kwargs):
+    # NB: _cw may be a server transaction or a request object.
+    #
+    # check user is in an allowed group, if so that's enough internal
+    # transactions should always stop there
+    DBG = False
+    if server.DEBUG & server.DBG_SEC:
+        if action in server._SECURITY_CAPS:
+            _self_str = str(self)
+            if server._SECURITY_ITEMS:
+                if any(item in _self_str for item in server._SECURITY_ITEMS):
+                    DBG = True
+            else:
+                DBG = True
+    groups = self.get_groups(action)
+    if _cw.user.matching_groups(groups):
+        if DBG:
+            print('check_perm: %r %r: user matches %s' % (action, _self_str, groups))
+        return
+    # if 'owners' in allowed groups, check if the user actually owns this
+    # object, if so that's enough
+    #
+    # NB: give _cw to user.owns since user is not be bound to a transaction on
+    # the repository side
+    if 'owners' in groups and (
+          kwargs.get('creating')
+          or ('eid' in kwargs and _cw.user.owns(kwargs['eid']))):
+        if DBG:
+            print('check_perm: %r %r: user is owner or creation time' %
+                  (action, _self_str))
+        return
+    # else if there is some rql expressions, check them
+    if DBG:
+        print('check_perm: %r %r %s' %
+              (action, _self_str, [(rqlexpr, kwargs, rqlexpr.check(_cw, **kwargs))
+                                   for rqlexpr in self.get_rqlexprs(action)]))
+    if any(rqlexpr.check(_cw, **kwargs)
+           for rqlexpr in self.get_rqlexprs(action)):
+        return
+    raise Unauthorized(action, str(self))
+PermissionMixIn.check_perm = check_perm
+
+
+CubicWebRelationDefinitionSchema._RPROPERTIES['eid'] = None
+# remember rproperties defined at this point. Others will have to be serialized in
+# CWAttribute.extra_props
+KNOWN_RPROPERTIES = CubicWebRelationDefinitionSchema.ALL_PROPERTIES()
+
+
+class CubicWebEntitySchema(EntitySchema):
+    """a entity has a type, a set of subject and or object relations
+    the entity schema defines the possible relations for a given type and some
+    constraints on those relations
+    """
+    def __init__(self, schema=None, edef=None, eid=None, **kwargs):
+        super(CubicWebEntitySchema, self).__init__(schema, edef, **kwargs)
+        if eid is None and edef is not None:
+            eid = getattr(edef, 'eid', None)
+        self.eid = eid
+
+    def targets(self, role):
+        assert role in ('subject', 'object')
+        if role == 'subject':
+            return self.subjrels.values()
+        return self.objrels.values()
+
+    @cachedproperty
+    def composite_rdef_roles(self):
+        """Return all relation definitions that define the current entity
+        type as a composite.
+        """
+        rdef_roles = []
+        for role in ('subject', 'object'):
+            for rschema in self.targets(role):
+                if rschema.final:
+                    continue
+                for rdef in rschema.rdefs.values():
+                    if (role == 'subject' and rdef.subject == self) or \
+                            (role == 'object' and rdef.object == self):
+                        crole = rdef.composite
+                        if crole == role:
+                            rdef_roles.append((rdef, role))
+        return rdef_roles
+
+    @cachedproperty
+    def is_composite(self):
+        return bool(len(self.composite_rdef_roles))
+
+    def check_permission_definitions(self):
+        super(CubicWebEntitySchema, self).check_permission_definitions()
+        for groups in self.permissions.values():
+            for group_or_rqlexpr in groups:
+                if isinstance(group_or_rqlexpr, RRQLExpression):
+                    msg = "can't use RRQLExpression on %s, use an ERQLExpression"
+                    raise BadSchemaDefinition(msg % self.type)
+
+    def is_subobject(self, strict=False, skiprels=None):
+        if skiprels is None:
+            skiprels = SKIP_COMPOSITE_RELS
+        else:
+            skiprels += SKIP_COMPOSITE_RELS
+        return super(CubicWebEntitySchema, self).is_subobject(strict,
+                                                              skiprels=skiprels)
+
+    def attribute_definitions(self):
+        """return an iterator on attribute definitions
+
+        attribute relations are a subset of subject relations where the
+        object's type is a final entity
+
+        an attribute definition is a 2-uple :
+        * name of the relation
+        * schema of the destination entity type
+        """
+        iter = super(CubicWebEntitySchema, self).attribute_definitions()
+        for rschema, attrschema in iter:
+            if rschema.type == 'has_text':
+                continue
+            yield rschema, attrschema
+
+    def main_attribute(self):
+        """convenience method that returns the *main* (i.e. the first non meta)
+        attribute defined in the entity schema
+        """
+        for rschema, _ in self.attribute_definitions():
+            if not (rschema in META_RTYPES
+                    or self.is_metadata(rschema)):
+                return rschema
+
+    def add_subject_relation(self, rschema):
+        """register the relation schema as possible subject relation"""
+        super(CubicWebEntitySchema, self).add_subject_relation(rschema)
+        if rschema.final:
+            if self.rdef(rschema).get('fulltextindexed'):
+                self._update_has_text()
+        elif rschema.fulltext_container:
+            self._update_has_text()
+
+    def add_object_relation(self, rschema):
+        """register the relation schema as possible object relation"""
+        super(CubicWebEntitySchema, self).add_object_relation(rschema)
+        if rschema.fulltext_container:
+            self._update_has_text()
+
+    def del_subject_relation(self, rtype):
+        super(CubicWebEntitySchema, self).del_subject_relation(rtype)
+        if 'has_text' in self.subjrels:
+            self._update_has_text(deletion=True)
+
+    def del_object_relation(self, rtype):
+        super(CubicWebEntitySchema, self).del_object_relation(rtype)
+        if 'has_text' in self.subjrels:
+            self._update_has_text(deletion=True)
+
+    def _update_has_text(self, deletion=False):
+        may_need_has_text, has_has_text = False, False
+        need_has_text = None
+        for rschema in self.subject_relations():
+            if rschema.final:
+                if rschema == 'has_text':
+                    has_has_text = True
+                elif self.rdef(rschema).get('fulltextindexed'):
+                    may_need_has_text = True
+            elif rschema.fulltext_container:
+                if rschema.fulltext_container == 'subject':
+                    may_need_has_text = True
+                else:
+                    need_has_text = False
+        for rschema in self.object_relations():
+            if rschema.fulltext_container:
+                if rschema.fulltext_container == 'object':
+                    may_need_has_text = True
+                else:
+                    need_has_text = False
+        if need_has_text is None:
+            need_has_text = may_need_has_text
+        if need_has_text and not has_has_text and not deletion:
+            rdef = ybo.RelationDefinition(self.type, 'has_text', 'String',
+                                          __permissions__=RO_ATTR_PERMS)
+            self.schema.add_relation_def(rdef)
+        elif not need_has_text and has_has_text:
+            # use rschema.del_relation_def and not schema.del_relation_def to
+            # avoid deleting the relation type accidentally...
+            self.schema['has_text'].del_relation_def(self, self.schema['String'])
+
+    def schema_entity(self): # XXX @property for consistency with meta
+        """return True if this entity type is used to build the schema"""
+        return self.type in SCHEMA_TYPES
+
+    def rql_expression(self, expression, mainvars=None, eid=None):
+        """rql expression factory"""
+        return ERQLExpression(expression, mainvars, eid)
+
+
+class CubicWebRelationSchema(PermissionMixIn, RelationSchema):
+    permissions = {}
+    ACTIONS = ()
+    rdef_class = CubicWebRelationDefinitionSchema
+
+    def __init__(self, schema=None, rdef=None, eid=None, **kwargs):
+        if rdef is not None:
+            # if this relation is inlined
+            self.inlined = rdef.inlined
+        super(CubicWebRelationSchema, self).__init__(schema, rdef, **kwargs)
+        if eid is None and rdef is not None:
+            eid = getattr(rdef, 'eid', None)
+        self.eid = eid
+
+    def init_computed_relation(self, rdef):
+        self.ACTIONS = ('read',)
+        super(CubicWebRelationSchema, self).init_computed_relation(rdef)
+
+    def advertise_new_add_permission(self):
+        pass
+
+    def check_permission_definitions(self):
+        RelationSchema.check_permission_definitions(self)
+        PermissionMixIn.check_permission_definitions(self)
+
+    @property
+    def meta(self):
+        return self.type in META_RTYPES
+
+    def schema_relation(self): # XXX @property for consistency with meta
+        """return True if this relation type is used to build the schema"""
+        return self.type in SCHEMA_TYPES
+
+    def may_have_permission(self, action, req, eschema=None, role=None):
+        if eschema is not None:
+            for tschema in self.targets(eschema, role):
+                rdef = self.role_rdef(eschema, tschema, role)
+                if rdef.may_have_permission(action, req):
+                    return True
+        else:
+            for rdef in self.rdefs.values():
+                if rdef.may_have_permission(action, req):
+                    return True
+        return False
+
+    def has_perm(self, _cw, action, **kwargs):
+        """return true if the action is granted globally or locally"""
+        if self.final:
+            assert not ('fromeid' in kwargs or 'toeid' in kwargs), kwargs
+            assert action in ('read', 'update')
+            if 'eid' in kwargs:
+                subjtype = _cw.entity_metas(kwargs['eid'])['type']
+            else:
+                subjtype = objtype = None
+        else:
+            assert not 'eid' in kwargs, kwargs
+            assert action in ('read', 'add', 'delete')
+            if 'fromeid' in kwargs:
+                subjtype = _cw.entity_metas(kwargs['fromeid'])['type']
+            elif 'frometype' in kwargs:
+                subjtype = kwargs.pop('frometype')
+            else:
+                subjtype = None
+            if 'toeid' in kwargs:
+                objtype = _cw.entity_metas(kwargs['toeid'])['type']
+            elif 'toetype' in kwargs:
+                objtype = kwargs.pop('toetype')
+            else:
+                objtype = None
+        if objtype and subjtype:
+            return self.rdef(subjtype, objtype).has_perm(_cw, action, **kwargs)
+        elif subjtype:
+            for tschema in self.targets(subjtype, 'subject'):
+                rdef = self.rdef(subjtype, tschema)
+                if not rdef.has_perm(_cw, action, **kwargs):
+                    return False
+        elif objtype:
+            for tschema in self.targets(objtype, 'object'):
+                rdef = self.rdef(tschema, objtype)
+                if not rdef.has_perm(_cw, action, **kwargs):
+                    return False
+        else:
+            for rdef in self.rdefs.values():
+                if not rdef.has_perm(_cw, action, **kwargs):
+                    return False
+        return True
+
+    @deprecated('use .rdef(subjtype, objtype).role_cardinality(role)')
+    def cardinality(self, subjtype, objtype, target):
+        return self.rdef(subjtype, objtype).role_cardinality(target)
+
+
+class CubicWebSchema(Schema):
+    """set of entities and relations schema defining the possible data sets
+    used in an application
+
+    :type name: str
+    :ivar name: name of the schema, usually the instance identifier
+
+    :type base: str
+    :ivar base: path of the directory where the schema is defined
+    """
+    reading_from_database = False
+    entity_class = CubicWebEntitySchema
+    relation_class = CubicWebRelationSchema
+    no_specialization_inference = ('identity',)
+
+    def __init__(self, *args, **kwargs):
+        self._eid_index = {}
+        super(CubicWebSchema, self).__init__(*args, **kwargs)
+        ybo.register_base_types(self)
+        rschema = self.add_relation_type(ybo.RelationType('eid'))
+        rschema.final = True
+        rschema = self.add_relation_type(ybo.RelationType('has_text'))
+        rschema.final = True
+        rschema = self.add_relation_type(ybo.RelationType('identity'))
+        rschema.final = False
+
+    etype_name_re = r'[A-Z][A-Za-z0-9]*[a-z]+[A-Za-z0-9]*$'
+    def add_entity_type(self, edef):
+        edef.name = str(edef.name)
+        edef.name = bw_normalize_etype(edef.name)
+        if not re.match(self.etype_name_re, edef.name):
+            raise BadSchemaDefinition(
+                '%r is not a valid name for an entity type. It should start '
+                'with an upper cased letter and be followed by at least a '
+                'lower cased letter' % edef.name)
+        eschema = super(CubicWebSchema, self).add_entity_type(edef)
+        if not eschema.final:
+            # automatically add the eid relation to non final entity types
+            rdef = ybo.RelationDefinition(eschema.type, 'eid', 'Int',
+                                          cardinality='11', uid=True,
+                                          __permissions__=RO_ATTR_PERMS)
+            self.add_relation_def(rdef)
+            rdef = ybo.RelationDefinition(eschema.type, 'identity', eschema.type,
+                                          __permissions__=RO_REL_PERMS)
+            self.add_relation_def(rdef)
+        self._eid_index[eschema.eid] = eschema
+        return eschema
+
+    def add_relation_type(self, rdef):
+        if not rdef.name.islower():
+            raise BadSchemaDefinition(
+                '%r is not a valid name for a relation type. It should be '
+                'lower cased' % rdef.name)
+        rdef.name = str(rdef.name)
+        rschema = super(CubicWebSchema, self).add_relation_type(rdef)
+        self._eid_index[rschema.eid] = rschema
+        return rschema
+
+    def add_relation_def(self, rdef):
+        """build a part of a relation schema
+        (i.e. add a relation between two specific entity's types)
+
+        :type subject: str
+        :param subject: entity's type that is subject of the relation
+
+        :type rtype: str
+        :param rtype: the relation's type (i.e. the name of the relation)
+
+        :type obj: str
+        :param obj: entity's type that is object of the relation
+
+        :rtype: RelationSchema
+        :param: the newly created or just completed relation schema
+        """
+        rdef.name = rdef.name.lower()
+        rdef.subject = bw_normalize_etype(rdef.subject)
+        rdef.object = bw_normalize_etype(rdef.object)
+        rdefs = super(CubicWebSchema, self).add_relation_def(rdef)
+        if rdefs:
+            try:
+                self._eid_index[rdef.eid] = rdefs
+            except AttributeError:
+                pass # not a serialized schema
+        return rdefs
+
+    def del_relation_type(self, rtype):
+        rschema = self.rschema(rtype)
+        self._eid_index.pop(rschema.eid, None)
+        super(CubicWebSchema, self).del_relation_type(rtype)
+
+    def del_relation_def(self, subjtype, rtype, objtype):
+        for k, v in self._eid_index.items():
+            if not isinstance(v, RelationDefinitionSchema):
+                continue
+            if v.subject == subjtype and v.rtype == rtype and v.object == objtype:
+                del self._eid_index[k]
+                break
+        super(CubicWebSchema, self).del_relation_def(subjtype, rtype, objtype)
+
+    def del_entity_type(self, etype):
+        eschema = self.eschema(etype)
+        self._eid_index.pop(eschema.eid, None)
+        # deal with has_text first, else its automatic deletion (see above)
+        # may trigger an error in ancestor's del_entity_type method
+        if 'has_text' in eschema.subject_relations():
+            self.del_relation_def(etype, 'has_text', 'String')
+        super(CubicWebSchema, self).del_entity_type(etype)
+
+    def schema_by_eid(self, eid):
+        return self._eid_index[eid]
+
+    def iter_computed_attributes(self):
+        for relation in self.relations():
+            for rdef in relation.rdefs.values():
+                if rdef.final and rdef.formula is not None:
+                    yield rdef
+
+    def iter_computed_relations(self):
+        for relation in self.relations():
+            if relation.rule:
+                yield relation
+
+    def finalize(self):
+        super(CubicWebSchema, self).finalize()
+        self.finalize_computed_attributes()
+        self.finalize_computed_relations()
+
+    def finalize_computed_attributes(self):
+        """Check computed attributes validity (if any), else raise
+        `BadSchemaDefinition`
+        """
+        analyzer = ETypeResolver(self)
+        for rdef in self.iter_computed_attributes():
+            rqlst = parse(rdef.formula)
+            select = rqlst.children[0]
+            select.add_type_restriction(select.defined_vars['X'], str(rdef.subject))
+            analyzer.visit(select)
+            _check_valid_formula(rdef, rqlst)
+            rdef.formula_select = select # avoid later recomputation
+
+
+    def finalize_computed_relations(self):
+        """Build relation definitions for computed relations
+
+        The subject and object types are infered using rql analyzer.
+        """
+        analyzer = ETypeResolver(self)
+        for rschema in self.iter_computed_relations():
+            # XXX rule is valid if both S and O are defined and not in an exists
+            rqlexpr = RRQLExpression(rschema.rule)
+            rqlst = rqlexpr.snippet_rqlst
+            analyzer.visit(rqlst)
+            couples = set((sol['S'], sol['O']) for sol in rqlst.solutions)
+            for subjtype, objtype in couples:
+                if self[objtype].final:
+                    raise BadSchemaDefinition('computed relations cannot be final')
+                rdef = ybo.RelationDefinition(
+                    subjtype, rschema.type, objtype,
+                    __permissions__={'add': (),
+                                     'delete': (),
+                                     'read': rschema.permissions['read']})
+                rdef.infered = True
+                self.add_relation_def(rdef)
+
+    def rebuild_infered_relations(self):
+        super(CubicWebSchema, self).rebuild_infered_relations()
+        self.finalize_computed_attributes()
+        self.finalize_computed_relations()
+
+
+# additional cw specific constraints ###########################################
+
+# these are implemented as CHECK constraints in sql, don't do the work
+# twice
+StaticVocabularyConstraint.check = lambda *args: True
+IntervalBoundConstraint.check = lambda *args: True
+BoundaryConstraint.check = lambda *args: True
+
+class BaseRQLConstraint(RRQLExpression, BaseConstraint):
+    """base class for rql constraints"""
+    distinct_query = None
+
+    def serialize(self):
+        # start with a semicolon for bw compat, see below
+        return ';' + ','.join(sorted(self.mainvars)) + ';' + self.expression
+
+    @classmethod
+    def deserialize(cls, value):
+        _, mainvars, expression = value.split(';', 2)
+        return cls(expression, mainvars)
+
+    def check(self, entity, rtype, value):
+        """return true if the value satisfy the constraint, else false"""
+        # implemented as a hook in the repository
+        return 1
+
+    def __str__(self):
+        if self.distinct_query:
+            selop = 'Any'
+        else:
+            selop = 'DISTINCT Any'
+        return '%s(%s %s WHERE %s)' % (self.__class__.__name__, selop,
+                                       ','.join(sorted(self.mainvars)),
+                                       self.expression)
+
+    def __repr__(self):
+        return '<%s @%#x>' % (self.__str__(), id(self))
+
+
+class RQLVocabularyConstraint(BaseRQLConstraint):
+    """the rql vocabulary constraint:
+
+    limits the proposed values to a set of entities returned by an rql query,
+    but this is not enforced at the repository level
+
+    `expression` is an additional rql restriction that will be added to
+    a predefined query, where the S and O variables respectively represent
+    the subject and the object of the relation
+
+    `mainvars` is a set of variables that should be used as selection variables
+    (i.e. `'Any %s WHERE ...' % mainvars`). If not specified, an attempt will be
+    made to guess it based on the variables used in the expression.
+    """
+
+    def repo_check(self, session, eidfrom, rtype, eidto):
+        """raise ValidationError if the relation doesn't satisfy the constraint
+        """
+        pass # this is a vocabulary constraint, not enforced
+
+
+class RepoEnforcedRQLConstraintMixIn(object):
+
+    def __init__(self, expression, mainvars=None, msg=None):
+        super(RepoEnforcedRQLConstraintMixIn, self).__init__(expression, mainvars)
+        self.msg = msg
+
+    def serialize(self):
+        # start with a semicolon for bw compat, see below
+        return ';%s;%s\n%s' % (','.join(sorted(self.mainvars)), self.expression,
+                               self.msg or '')
+
+    @classmethod
+    def deserialize(cls, value):
+        value, msg = value.split('\n', 1)
+        _, mainvars, expression = value.split(';', 2)
+        return cls(expression, mainvars, msg)
+
+    def repo_check(self, session, eidfrom, rtype, eidto=None):
+        """raise ValidationError if the relation doesn't satisfy the constraint
+        """
+        if not self.match_condition(session, eidfrom, eidto):
+            # XXX at this point if both or neither of S and O are in mainvar we
+            # dunno if the validation error `occurred` on eidfrom or eidto (from
+            # user interface point of view)
+            #
+            # possible enhancement: check entity being created, it's probably
+            # the main eid unless this is a composite relation
+            if eidto is None or 'S' in self.mainvars or not 'O' in self.mainvars:
+                maineid = eidfrom
+                qname = role_name(rtype, 'subject')
+            else:
+                maineid = eidto
+                qname = role_name(rtype, 'object')
+            if self.msg:
+                msg = session._(self.msg)
+            else:
+                msg = '%(constraint)s %(expression)s failed' % {
+                    'constraint':  session._(self.type()),
+                    'expression': self.expression}
+            raise ValidationError(maineid, {qname: msg})
+
+    def exec_query(self, _cw, eidfrom, eidto):
+        if eidto is None:
+            # checking constraint for an attribute relation
+            expression = 'S eid %(s)s, ' + self.expression
+            args = {'s': eidfrom}
+        else:
+            expression = 'S eid %(s)s, O eid %(o)s, ' + self.expression
+            args = {'s': eidfrom, 'o': eidto}
+        if 'U' in self.rqlst.defined_vars:
+            expression = 'U eid %(u)s, ' + expression
+            args['u'] = _cw.user.eid
+        rql = 'Any %s WHERE %s' % (','.join(sorted(self.mainvars)), expression)
+        if self.distinct_query:
+            rql = 'DISTINCT ' + rql
+        return _cw.execute(rql, args, build_descr=False)
+
+
+class RQLConstraint(RepoEnforcedRQLConstraintMixIn, BaseRQLConstraint):
+    """the rql constraint is similar to the RQLVocabularyConstraint but
+    are also enforced at the repository level
+    """
+    distinct_query = False
+
+    def match_condition(self, session, eidfrom, eidto):
+        return self.exec_query(session, eidfrom, eidto)
+
+
+class RQLUniqueConstraint(RepoEnforcedRQLConstraintMixIn, BaseRQLConstraint):
+    """the unique rql constraint check that the result of the query isn't
+    greater than one.
+
+    You *must* specify `mainvars` when instantiating the constraint since there
+    is no way to guess it correctly (e.g. if using S,O or U the constraint will
+    always be satisfied because we've to use a DISTINCT query).
+    """
+    # XXX turns mainvars into a required argument in __init__
+    distinct_query = True
+
+    def match_condition(self, session, eidfrom, eidto):
+        return len(self.exec_query(session, eidfrom, eidto)) <= 1
+
+
+# workflow extensions #########################################################
+
+from yams.buildobjs import _add_relation as yams_add_relation
+
+class workflowable_definition(ybo.metadefinition):
+    """extends default EntityType's metaclass to add workflow relations
+    (i.e. in_state, wf_info_for and custom_workflow). This is the default
+    metaclass for WorkflowableEntityType.
+    """
+    def __new__(mcs, name, bases, classdict):
+        abstract = classdict.pop('__abstract__', False)
+        cls = super(workflowable_definition, mcs).__new__(mcs, name, bases,
+                                                          classdict)
+        if not abstract:
+            make_workflowable(cls)
+        return cls
+
+
+@add_metaclass(workflowable_definition)
+class WorkflowableEntityType(ybo.EntityType):
+    """Use this base class instead of :class:`EntityType` to have workflow
+    relations (i.e. `in_state`, `wf_info_for` and `custom_workflow`) on your
+    entity type.
+    """
+    __abstract__ = True
+
+
+def make_workflowable(cls, in_state_descr=None):
+    """Adds workflow relations as :class:`WorkflowableEntityType`, but usable on
+    existing classes which are not using that base class.
+    """
+    existing_rels = set(rdef.name for rdef in cls.__relations__)
+    # let relation types defined in cw.schemas.workflow carrying
+    # cardinality, constraints and other relation definition properties
+    etype = getattr(cls, 'name', cls.__name__)
+    if 'custom_workflow' not in existing_rels:
+        rdef = ybo.RelationDefinition(etype, 'custom_workflow', 'Workflow')
+        yams_add_relation(cls.__relations__, rdef)
+    if 'in_state' not in existing_rels:
+        rdef = ybo.RelationDefinition(etype, 'in_state', 'State',
+                                      description=in_state_descr)
+        yams_add_relation(cls.__relations__, rdef)
+    if 'wf_info_for' not in existing_rels:
+        rdef = ybo.RelationDefinition('TrInfo', 'wf_info_for', etype)
+        yams_add_relation(cls.__relations__, rdef)
+
+
+# schema loading ##############################################################
+
+CONSTRAINTS['RQLConstraint'] = RQLConstraint
+CONSTRAINTS['RQLUniqueConstraint'] = RQLUniqueConstraint
+CONSTRAINTS['RQLVocabularyConstraint'] = RQLVocabularyConstraint
+CONSTRAINTS.pop('MultipleStaticVocabularyConstraint', None) # don't want this in cw yams schema
+PyFileReader.context.update(CONSTRAINTS)
+
+
+class BootstrapSchemaLoader(SchemaLoader):
+    """cubicweb specific schema loader, loading only schema necessary to read
+    the persistent schema
+    """
+    schemacls = CubicWebSchema
+
+    def load(self, config, path=(), **kwargs):
+        """return a Schema instance from the schema definition read
+        from <directory>
+        """
+        return super(BootstrapSchemaLoader, self).load(
+            path, config.appid, register_base_types=False, **kwargs)
+
+    def _load_definition_files(self, cubes=None):
+        # bootstraping, ignore cubes
+        filepath = join(cubicweb.CW_SOFTWARE_ROOT, 'schemas', 'bootstrap.py')
+        self.info('loading %s', filepath)
+        with tempattr(ybo, 'PACKAGE', 'cubicweb'): # though we don't care here
+            self.handle_file(filepath)
+
+    def unhandled_file(self, filepath):
+        """called when a file without handler associated has been found"""
+        self.warning('ignoring file %r', filepath)
+
+    # these are overridden by set_log_methods below
+    # only defining here to prevent pylint from complaining
+    info = warning = error = critical = exception = debug = lambda msg,*a,**kw: None
+
+class CubicWebSchemaLoader(BootstrapSchemaLoader):
+    """cubicweb specific schema loader, automatically adding metadata to the
+    instance's schema
+    """
+
+    def load(self, config, **kwargs):
+        """return a Schema instance from the schema definition read
+        from <directory>
+        """
+        self.info('loading %s schemas', ', '.join(config.cubes()))
+        self.extrapath = {}
+        for cubesdir in config.cubes_search_path():
+            if cubesdir != config.CUBES_DIR:
+                self.extrapath[cubesdir] = 'cubes'
+        if config.apphome:
+            path = tuple(reversed([config.apphome] + config.cubes_path()))
+        else:
+            path = tuple(reversed(config.cubes_path()))
+        try:
+            return super(CubicWebSchemaLoader, self).load(config, path=path, **kwargs)
+        finally:
+            # we've to cleanup modules imported from cubicweb.schemas as well
+            cleanup_sys_modules([join(cubicweb.CW_SOFTWARE_ROOT, 'schemas')])
+
+    def _load_definition_files(self, cubes):
+        for filepath in (join(cubicweb.CW_SOFTWARE_ROOT, 'schemas', 'bootstrap.py'),
+                         join(cubicweb.CW_SOFTWARE_ROOT, 'schemas', 'base.py'),
+                         join(cubicweb.CW_SOFTWARE_ROOT, 'schemas', 'workflow.py'),
+                         join(cubicweb.CW_SOFTWARE_ROOT, 'schemas', 'Bookmark.py')):
+            self.info('loading %s', filepath)
+            with tempattr(ybo, 'PACKAGE', 'cubicweb'):
+                self.handle_file(filepath)
+        for cube in cubes:
+            for filepath in self.get_schema_files(cube):
+                with tempattr(ybo, 'PACKAGE', basename(cube)):
+                    self.handle_file(filepath)
+
+    # these are overridden by set_log_methods below
+    # only defining here to prevent pylint from complaining
+    info = warning = error = critical = exception = debug = lambda msg,*a,**kw: None
+
+
+set_log_methods(CubicWebSchemaLoader, getLogger('cubicweb.schemaloader'))
+set_log_methods(BootstrapSchemaLoader, getLogger('cubicweb.bootstrapschemaloader'))
+set_log_methods(RQLExpression, getLogger('cubicweb.schema'))
+
+# _() is just there to add messages to the catalog, don't care about actual
+# translation
+MAY_USE_TEMPLATE_FORMAT = set(('managers',))
+NEED_PERM_FORMATS = [_('text/cubicweb-page-template')]
+
+@monkeypatch(FormatConstraint)
+def vocabulary(self, entity=None, form=None):
+    cw = None
+    if form is None and entity is not None:
+        cw = entity._cw
+    elif form is not None:
+        cw = form._cw
+    if cw is not None:
+        if hasattr(cw, 'write_security'): # test it's a session and not a request
+            # cw is a server session
+            hasperm = not cw.write_security or \
+                      not cw.is_hook_category_activated('integrity') or \
+                      cw.user.matching_groups(MAY_USE_TEMPLATE_FORMAT)
+        else:
+            hasperm = cw.user.matching_groups(MAY_USE_TEMPLATE_FORMAT)
+        if hasperm:
+            return self.regular_formats + tuple(NEED_PERM_FORMATS)
+    return self.regular_formats
+
+# XXX itou for some Statement methods
+from rql import stmts
+orig_get_etype = stmts.ScopeNode.get_etype
+def bw_get_etype(self, name):
+    return orig_get_etype(self, bw_normalize_etype(name))
+stmts.ScopeNode.get_etype = bw_get_etype
+
+orig_add_main_variable_delete = stmts.Delete.add_main_variable
+def bw_add_main_variable_delete(self, etype, vref):
+    return orig_add_main_variable_delete(self, bw_normalize_etype(etype), vref)
+stmts.Delete.add_main_variable = bw_add_main_variable_delete
+
+orig_add_main_variable_insert = stmts.Insert.add_main_variable
+def bw_add_main_variable_insert(self, etype, vref):
+    return orig_add_main_variable_insert(self, bw_normalize_etype(etype), vref)
+stmts.Insert.add_main_variable = bw_add_main_variable_insert
+
+orig_set_statement_type = stmts.Select.set_statement_type
+def bw_set_statement_type(self, etype):
+    return orig_set_statement_type(self, bw_normalize_etype(etype))
+stmts.Select.set_statement_type = bw_set_statement_type