diff --git a/requirements.txt b/requirements.txt
index ec9e41d1..85c6e7de 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -6,7 +6,6 @@ furl>=2.0.0
 future>=0.16.0
 futures>=3.0.5 ; python_version < '3'
 humanfriendly>=2.1
-jsonmodels>=2.2
 jsonschema>=2.6.0
 numpy>=1.10
 pathlib2>=2.3.0
diff --git a/trains/backend_api/session/jsonmodels/__init__.py b/trains/backend_api/session/jsonmodels/__init__.py
new file mode 100644
index 00000000..1f700d8f
--- /dev/null
+++ b/trains/backend_api/session/jsonmodels/__init__.py
@@ -0,0 +1,9 @@
+# coding: utf-8
+
+__author__ = 'Szczepan Cieślik'
+__email__ = 'szczepan.cieslik@gmail.com'
+__version__ = '2.4'
+
+from . import models
+from . import fields
+from . import errors
diff --git a/trains/backend_api/session/jsonmodels/builders.py b/trains/backend_api/session/jsonmodels/builders.py
new file mode 100644
index 00000000..719f47fb
--- /dev/null
+++ b/trains/backend_api/session/jsonmodels/builders.py
@@ -0,0 +1,230 @@
+"""Builders to generate in memory representation of model and fields tree."""
+
+from __future__ import absolute_import
+
+from collections import defaultdict
+
+import six
+
+from . import errors
+from .fields import NotSet
+
+
+class Builder(object):
+
+    def __init__(self, parent=None, nullable=False, default=NotSet):
+        self.parent = parent
+        self.types_builders = {}
+        self.types_count = defaultdict(int)
+        self.definitions = set()
+        self.nullable = nullable
+        self.default = default
+
+    @property
+    def has_default(self):
+        return self.default is not NotSet
+
+    def register_type(self, type, builder):
+        if self.parent:
+            return self.parent.register_type(type, builder)
+
+        self.types_count[type] += 1
+        if type not in self.types_builders:
+            self.types_builders[type] = builder
+
+    def get_builder(self, type):
+        if self.parent:
+            return self.parent.get_builder(type)
+
+        return self.types_builders[type]
+
+    def count_type(self, type):
+        if self.parent:
+            return self.parent.count_type(type)
+
+        return self.types_count[type]
+
+    @staticmethod
+    def maybe_build(value):
+        return value.build() if isinstance(value, Builder) else value
+
+    def add_definition(self, builder):
+        if self.parent:
+            return self.parent.add_definition(builder)
+
+        self.definitions.add(builder)
+
+
+class ObjectBuilder(Builder):
+
+    def __init__(self, model_type, *args, **kwargs):
+        super(ObjectBuilder, self).__init__(*args, **kwargs)
+        self.properties = {}
+        self.required = []
+        self.type = model_type
+
+        self.register_type(self.type, self)
+
+    def add_field(self, name, field, schema):
+        _apply_validators_modifications(schema, field)
+        self.properties[name] = schema
+        if field.required:
+            self.required.append(name)
+
+    def build(self):
+        builder = self.get_builder(self.type)
+        if self.is_definition and not self.is_root:
+            self.add_definition(builder)
+            [self.maybe_build(value) for _, value in self.properties.items()]
+            return '#/definitions/{name}'.format(name=self.type_name)
+        else:
+            return builder.build_definition(nullable=self.nullable)
+
+    @property
+    def type_name(self):
+        module_name = '{module}.{name}'.format(
+            module=self.type.__module__,
+            name=self.type.__name__,
+        )
+        return module_name.replace('.', '_').lower()
+
+    def build_definition(self, add_defintitions=True, nullable=False):
+        properties = dict(
+            (name, self.maybe_build(value))
+            for name, value
+            in self.properties.items()
+        )
+        schema = {
+            'type': 'object',
+            'additionalProperties': False,
+            'properties': properties,
+        }
+        if self.required:
+            schema['required'] = self.required
+        if self.definitions and add_defintitions:
+            schema['definitions'] = dict(
+                (builder.type_name, builder.build_definition(False, False))
+                for builder in self.definitions
+            )
+        return schema
+
+    @property
+    def is_definition(self):
+        if self.count_type(self.type) > 1:
+            return True
+        elif self.parent:
+            return self.parent.is_definition
+        else:
+            return False
+
+    @property
+    def is_root(self):
+        return not bool(self.parent)
+
+
+def _apply_validators_modifications(field_schema, field):
+    for validator in field.validators:
+        try:
+            validator.modify_schema(field_schema)
+        except AttributeError:
+            pass
+
+
+class PrimitiveBuilder(Builder):
+
+    def __init__(self, type, *args, **kwargs):
+        super(PrimitiveBuilder, self).__init__(*args, **kwargs)
+        self.type = type
+
+    def build(self):
+        schema = {}
+        if issubclass(self.type, six.string_types):
+            obj_type = 'string'
+        elif issubclass(self.type, bool):
+            obj_type = 'boolean'
+        elif issubclass(self.type, int):
+            obj_type = 'number'
+        elif issubclass(self.type, float):
+            obj_type = 'number'
+        else:
+            raise errors.FieldNotSupported(
+                "Can't specify value schema!", self.type
+            )
+
+        if self.nullable:
+            obj_type = [obj_type, 'null']
+        schema['type'] = obj_type
+
+        if self.has_default:
+            schema["default"] = self.default
+
+        return schema
+
+
+class ListBuilder(Builder):
+
+    def __init__(self, *args, **kwargs):
+        super(ListBuilder, self).__init__(*args, **kwargs)
+        self.schemas = []
+
+    def add_type_schema(self, schema):
+        self.schemas.append(schema)
+
+    def build(self):
+        schema = {'type': 'array'}
+        if self.nullable:
+            self.add_type_schema({'type': 'null'})
+
+        if self.has_default:
+            schema["default"] = [self.to_struct(i) for i in self.default]
+
+        schemas = [self.maybe_build(s) for s in self.schemas]
+        if len(schemas) == 1:
+            items = schemas[0]
+        else:
+            items = {'oneOf': schemas}
+
+        schema['items'] = items
+        return schema
+
+    @property
+    def is_definition(self):
+        return self.parent.is_definition
+
+    @staticmethod
+    def to_struct(item):
+        from .models import Base
+        if isinstance(item, Base):
+            return item.to_struct()
+        return item
+
+
+class EmbeddedBuilder(Builder):
+
+    def __init__(self, *args, **kwargs):
+        super(EmbeddedBuilder, self).__init__(*args, **kwargs)
+        self.schemas = []
+
+    def add_type_schema(self, schema):
+        self.schemas.append(schema)
+
+    def build(self):
+        if self.nullable:
+            self.add_type_schema({'type': 'null'})
+
+        schemas = [self.maybe_build(schema) for schema in self.schemas]
+        if len(schemas) == 1:
+            schema = schemas[0]
+        else:
+            schema = {'oneOf': schemas}
+
+        if self.has_default:
+            # The default value of EmbeddedField is expected to be an instance
+            # of a subclass of models.Base, thus have `to_struct`
+            schema["default"] = self.default.to_struct()
+
+        return schema
+
+    @property
+    def is_definition(self):
+        return self.parent.is_definition
diff --git a/trains/backend_api/session/jsonmodels/collections.py b/trains/backend_api/session/jsonmodels/collections.py
new file mode 100644
index 00000000..950af96b
--- /dev/null
+++ b/trains/backend_api/session/jsonmodels/collections.py
@@ -0,0 +1,21 @@
+
+
+class ModelCollection(list):
+
+    """`ModelCollection` is list which validates stored values.
+
+    Validation is made with use of field passed to `__init__` at each point,
+    when new value is assigned.
+
+    """
+
+    def __init__(self, field):
+        self.field = field
+
+    def append(self, value):
+        self.field.validate_single_value(value)
+        super(ModelCollection, self).append(value)
+
+    def __setitem__(self, key, value):
+        self.field.validate_single_value(value)
+        super(ModelCollection, self).__setitem__(key, value)
diff --git a/trains/backend_api/session/jsonmodels/errors.py b/trains/backend_api/session/jsonmodels/errors.py
new file mode 100644
index 00000000..23b933bf
--- /dev/null
+++ b/trains/backend_api/session/jsonmodels/errors.py
@@ -0,0 +1,15 @@
+
+
+class ValidationError(RuntimeError):
+
+    pass
+
+
+class FieldNotFound(RuntimeError):
+
+    pass
+
+
+class FieldNotSupported(ValueError):
+
+    pass
diff --git a/trains/backend_api/session/jsonmodels/fields.py b/trains/backend_api/session/jsonmodels/fields.py
new file mode 100644
index 00000000..722c833b
--- /dev/null
+++ b/trains/backend_api/session/jsonmodels/fields.py
@@ -0,0 +1,488 @@
+import datetime
+import re
+from weakref import WeakKeyDictionary
+
+import six
+from dateutil.parser import parse
+
+from .errors import ValidationError
+from .collections import ModelCollection
+
+
+# unique marker for "no default value specified". None is not good enough since
+# it is a completely valid default value.
+NotSet = object()
+
+
+class BaseField(object):
+
+    """Base class for all fields."""
+
+    types = None
+
+    def __init__(
+            self,
+            required=False,
+            nullable=False,
+            help_text=None,
+            validators=None,
+            default=NotSet,
+            name=None):
+        self.memory = WeakKeyDictionary()
+        self.required = required
+        self.help_text = help_text
+        self.nullable = nullable
+        self._assign_validators(validators)
+        self.name = name
+        self._validate_name()
+        if default is not NotSet:
+            self.validate(default)
+        self._default = default
+
+    @property
+    def has_default(self):
+        return self._default is not NotSet
+
+    def _assign_validators(self, validators):
+        if validators and not isinstance(validators, list):
+            validators = [validators]
+        self.validators = validators or []
+
+    def __set__(self, instance, value):
+        self._finish_initialization(type(instance))
+        value = self.parse_value(value)
+        self.validate(value)
+        self.memory[instance._cache_key] = value
+
+    def __get__(self, instance, owner=None):
+        if instance is None:
+            self._finish_initialization(owner)
+            return self
+
+        self._finish_initialization(type(instance))
+
+        self._check_value(instance)
+        return self.memory[instance._cache_key]
+
+    def _finish_initialization(self, owner):
+        pass
+
+    def _check_value(self, obj):
+        if obj._cache_key not in self.memory:
+            self.__set__(obj, self.get_default_value())
+
+    def validate_for_object(self, obj):
+        value = self.__get__(obj)
+        self.validate(value)
+
+    def validate(self, value):
+        self._check_types()
+        self._validate_against_types(value)
+        self._check_against_required(value)
+        self._validate_with_custom_validators(value)
+
+    def _check_against_required(self, value):
+        if value is None and self.required:
+            raise ValidationError('Field is required!')
+
+    def _validate_against_types(self, value):
+        if value is not None and not isinstance(value, self.types):
+            raise ValidationError(
+                'Value is wrong, expected type "{types}"'.format(
+                    types=', '.join([t.__name__ for t in self.types])
+                ),
+                value,
+            )
+
+    def _check_types(self):
+        if self.types is None:
+            raise ValidationError(
+                'Field "{type}" is not usable, try '
+                'different field type.'.format(type=type(self).__name__))
+
+    def to_struct(self, value):
+        """Cast value to Python structure."""
+        return value
+
+    def parse_value(self, value):
+        """Parse value from primitive to desired format.
+
+        Each field can parse value to form it wants it to be (like string or
+        int).
+
+        """
+        return value
+
+    def _validate_with_custom_validators(self, value):
+        if value is None and self.nullable:
+            return
+
+        for validator in self.validators:
+            try:
+                validator.validate(value)
+            except AttributeError:
+                validator(value)
+
+    def get_default_value(self):
+        """Get default value for field.
+
+        Each field can specify its default.
+
+        """
+        return self._default if self.has_default else None
+
+    def _validate_name(self):
+        if self.name is None:
+            return
+        if not re.match('^[A-Za-z_](([\w\-]*)?\w+)?$', self.name):
+            raise ValueError('Wrong name', self.name)
+
+    def structue_name(self, default):
+        return self.name if self.name is not None else default
+
+
+class StringField(BaseField):
+
+    """String field."""
+
+    types = six.string_types
+
+
+class IntField(BaseField):
+
+    """Integer field."""
+
+    types = (int,)
+
+    def parse_value(self, value):
+        """Cast value to `int`, e.g. from string or long"""
+        parsed = super(IntField, self).parse_value(value)
+        if parsed is None:
+            return parsed
+        return int(parsed)
+
+
+class FloatField(BaseField):
+
+    """Float field."""
+
+    types = (float, int)
+
+
+class BoolField(BaseField):
+
+    """Bool field."""
+
+    types = (bool,)
+
+    def parse_value(self, value):
+        """Cast value to `bool`."""
+        parsed = super(BoolField, self).parse_value(value)
+        return bool(parsed) if parsed is not None else None
+
+
+class ListField(BaseField):
+
+    """List field."""
+
+    types = (list,)
+
+    def __init__(self, items_types=None, *args, **kwargs):
+        """Init.
+
+        `ListField` is **always not required**. If you want to control number
+        of items use validators.
+
+        """
+        self._assign_types(items_types)
+        super(ListField, self).__init__(*args, **kwargs)
+        self.required = False
+
+    def get_default_value(self):
+        default = super(ListField, self).get_default_value()
+        if default is None:
+            return ModelCollection(self)
+        return default
+
+    def _assign_types(self, items_types):
+        if items_types:
+            try:
+                self.items_types = tuple(items_types)
+            except TypeError:
+                self.items_types = items_types,
+        else:
+            self.items_types = tuple()
+
+        types = []
+        for type_ in self.items_types:
+            if isinstance(type_, six.string_types):
+                types.append(_LazyType(type_))
+            else:
+                types.append(type_)
+        self.items_types = tuple(types)
+
+    def validate(self, value):
+        super(ListField, self).validate(value)
+
+        if len(self.items_types) == 0:
+            return
+
+        for item in value:
+            self.validate_single_value(item)
+
+    def validate_single_value(self, item):
+        if len(self.items_types) == 0:
+            return
+
+        if not isinstance(item, self.items_types):
+            raise ValidationError(
+                'All items must be instances '
+                'of "{types}", and not "{type}".'.format(
+                    types=', '.join([t.__name__ for t in self.items_types]),
+                    type=type(item).__name__,
+                ))
+
+    def parse_value(self, values):
+        """Cast value to proper collection."""
+        result = self.get_default_value()
+
+        if not values:
+            return result
+
+        if not isinstance(values, list):
+            return values
+
+        return [self._cast_value(value) for value in values]
+
+    def _cast_value(self, value):
+        if isinstance(value, self.items_types):
+            return value
+        else:
+            if len(self.items_types) != 1:
+                tpl = 'Cannot decide which type to choose from "{types}".'
+                raise ValidationError(
+                    tpl.format(
+                        types=', '.join([t.__name__ for t in self.items_types])
+                    )
+                )
+            return self.items_types[0](**value)
+
+    def _finish_initialization(self, owner):
+        super(ListField, self)._finish_initialization(owner)
+
+        types = []
+        for type in self.items_types:
+            if isinstance(type, _LazyType):
+                types.append(type.evaluate(owner))
+            else:
+                types.append(type)
+        self.items_types = tuple(types)
+
+    def _elem_to_struct(self, value):
+        try:
+            return value.to_struct()
+        except AttributeError:
+            return value
+
+    def to_struct(self, values):
+        return [self._elem_to_struct(v) for v in values]
+
+
+class EmbeddedField(BaseField):
+
+    """Field for embedded models."""
+
+    def __init__(self, model_types, *args, **kwargs):
+        self._assign_model_types(model_types)
+        super(EmbeddedField, self).__init__(*args, **kwargs)
+
+    def _assign_model_types(self, model_types):
+        if not isinstance(model_types, (list, tuple)):
+            model_types = (model_types,)
+
+        types = []
+        for type_ in model_types:
+            if isinstance(type_, six.string_types):
+                types.append(_LazyType(type_))
+            else:
+                types.append(type_)
+        self.types = tuple(types)
+
+    def _finish_initialization(self, owner):
+        super(EmbeddedField, self)._finish_initialization(owner)
+
+        types = []
+        for type in self.types:
+            if isinstance(type, _LazyType):
+                types.append(type.evaluate(owner))
+            else:
+                types.append(type)
+        self.types = tuple(types)
+
+    def validate(self, value):
+        super(EmbeddedField, self).validate(value)
+        try:
+            value.validate()
+        except AttributeError:
+            pass
+
+    def parse_value(self, value):
+        """Parse value to proper model type."""
+        if not isinstance(value, dict):
+            return value
+
+        embed_type = self._get_embed_type()
+        return embed_type(**value)
+
+    def _get_embed_type(self):
+        if len(self.types) != 1:
+            raise ValidationError(
+                'Cannot decide which type to choose from "{types}".'.format(
+                    types=', '.join([t.__name__ for t in self.types])
+                )
+            )
+        return self.types[0]
+
+    def to_struct(self, value):
+        return value.to_struct()
+
+
+class _LazyType(object):
+
+    def __init__(self, path):
+        self.path = path
+
+    def evaluate(self, base_cls):
+        module, type_name = _evaluate_path(self.path, base_cls)
+        return _import(module, type_name)
+
+
+def _evaluate_path(relative_path, base_cls):
+    base_module = base_cls.__module__
+
+    modules = _get_modules(relative_path, base_module)
+
+    type_name = modules.pop()
+    module = '.'.join(modules)
+    if not module:
+        module = base_module
+    return module, type_name
+
+
+def _get_modules(relative_path, base_module):
+    canonical_path = relative_path.lstrip('.')
+    canonical_modules = canonical_path.split('.')
+
+    if not relative_path.startswith('.'):
+        return canonical_modules
+
+    parents_amount = len(relative_path) - len(canonical_path)
+    parent_modules = base_module.split('.')
+    parents_amount = max(0, parents_amount - 1)
+    if parents_amount > len(parent_modules):
+        raise ValueError("Can't evaluate path '{}'".format(relative_path))
+    return parent_modules[:parents_amount * -1] + canonical_modules
+
+
+def _import(module_name, type_name):
+    module = __import__(module_name, fromlist=[type_name])
+    try:
+        return getattr(module, type_name)
+    except AttributeError:
+        raise ValueError(
+            "Can't find type '{}.{}'.".format(module_name, type_name))
+
+
+class TimeField(StringField):
+
+    """Time field."""
+
+    types = (datetime.time,)
+
+    def __init__(self, str_format=None, *args, **kwargs):
+        """Init.
+
+        :param str str_format: Format to cast time to (if `None` - casting to
+            ISO 8601 format).
+
+        """
+        self.str_format = str_format
+        super(TimeField, self).__init__(*args, **kwargs)
+
+    def to_struct(self, value):
+        """Cast `time` object to string."""
+        if self.str_format:
+            return value.strftime(self.str_format)
+        return value.isoformat()
+
+    def parse_value(self, value):
+        """Parse string into instance of `time`."""
+        if value is None:
+            return value
+        if isinstance(value, datetime.time):
+            return value
+        return parse(value).timetz()
+
+
+class DateField(StringField):
+
+    """Date field."""
+
+    types = (datetime.date,)
+    default_format = '%Y-%m-%d'
+
+    def __init__(self, str_format=None, *args, **kwargs):
+        """Init.
+
+        :param str str_format: Format to cast date to (if `None` - casting to
+            %Y-%m-%d format).
+
+        """
+        self.str_format = str_format
+        super(DateField, self).__init__(*args, **kwargs)
+
+    def to_struct(self, value):
+        """Cast `date` object to string."""
+        if self.str_format:
+            return value.strftime(self.str_format)
+        return value.strftime(self.default_format)
+
+    def parse_value(self, value):
+        """Parse string into instance of `date`."""
+        if value is None:
+            return value
+        if isinstance(value, datetime.date):
+            return value
+        return parse(value).date()
+
+
+class DateTimeField(StringField):
+
+    """Datetime field."""
+
+    types = (datetime.datetime,)
+
+    def __init__(self, str_format=None, *args, **kwargs):
+        """Init.
+
+        :param str str_format: Format to cast datetime to (if `None` - casting
+            to ISO 8601 format).
+
+        """
+        self.str_format = str_format
+        super(DateTimeField, self).__init__(*args, **kwargs)
+
+    def to_struct(self, value):
+        """Cast `datetime` object to string."""
+        if self.str_format:
+            return value.strftime(self.str_format)
+        return value.isoformat()
+
+    def parse_value(self, value):
+        """Parse string into instance of `datetime`."""
+        if isinstance(value, datetime.datetime):
+            return value
+        if value:
+            return parse(value)
+        else:
+            return None
diff --git a/trains/backend_api/session/jsonmodels/models.py b/trains/backend_api/session/jsonmodels/models.py
new file mode 100644
index 00000000..da4bbac0
--- /dev/null
+++ b/trains/backend_api/session/jsonmodels/models.py
@@ -0,0 +1,154 @@
+import six
+
+from . import parsers, errors
+from .fields import BaseField
+from .errors import ValidationError
+
+
+class JsonmodelMeta(type):
+
+    def __new__(cls, name, bases, attributes):
+        cls.validate_fields(attributes)
+        return super(cls, cls).__new__(cls, name, bases, attributes)
+
+    @staticmethod
+    def validate_fields(attributes):
+        fields = {
+            key: value for key, value in attributes.items()
+            if isinstance(value, BaseField)
+        }
+        taken_names = set()
+        for name, field in fields.items():
+            structue_name = field.structue_name(name)
+            if structue_name in taken_names:
+                raise ValueError('Name taken', structue_name, name)
+            taken_names.add(structue_name)
+
+
+class Base(six.with_metaclass(JsonmodelMeta, object)):
+
+    """Base class for all models."""
+
+    def __init__(self, **kwargs):
+        self._cache_key = _CacheKey()
+        self.populate(**kwargs)
+
+    def populate(self, **values):
+        """Populate values to fields. Skip non-existing."""
+        values = values.copy()
+        fields = list(self.iterate_with_name())
+        for _, structure_name, field in fields:
+            if structure_name in values:
+                field.__set__(self, values.pop(structure_name))
+        for name, _, field in fields:
+            if name in values:
+                field.__set__(self, values.pop(name))
+
+    def get_field(self, field_name):
+        """Get field associated with given attribute."""
+        for attr_name, field in self:
+            if field_name == attr_name:
+                return field
+
+        raise errors.FieldNotFound('Field not found', field_name)
+
+    def __iter__(self):
+        """Iterate through fields and values."""
+        for name, field in self.iterate_over_fields():
+            yield name, field
+
+    def validate(self):
+        """Explicitly validate all the fields."""
+        for name, field in self:
+            try:
+                field.validate_for_object(self)
+            except ValidationError as error:
+                raise ValidationError(
+                    "Error for field '{name}'.".format(name=name),
+                    error,
+                )
+
+    @classmethod
+    def iterate_over_fields(cls):
+        """Iterate through fields as `(attribute_name, field_instance)`."""
+        for attr in dir(cls):
+            clsattr = getattr(cls, attr)
+            if isinstance(clsattr, BaseField):
+                yield attr, clsattr
+
+    @classmethod
+    def iterate_with_name(cls):
+        """Iterate over fields, but also give `structure_name`.
+
+        Format is `(attribute_name, structue_name, field_instance)`.
+        Structure name is name under which value is seen in structure and
+        schema (in primitives) and only there.
+        """
+        for attr_name, field in cls.iterate_over_fields():
+            structure_name = field.structue_name(attr_name)
+            yield attr_name, structure_name, field
+
+    def to_struct(self):
+        """Cast model to Python structure."""
+        return parsers.to_struct(self)
+
+    @classmethod
+    def to_json_schema(cls):
+        """Generate JSON schema for model."""
+        return parsers.to_json_schema(cls)
+
+    def __repr__(self):
+        attrs = {}
+        for name, _ in self:
+            try:
+                attr = getattr(self, name)
+                if attr is not None:
+                    attrs[name] = repr(attr)
+            except ValidationError:
+                pass
+
+        return '{class_name}({fields})'.format(
+            class_name=self.__class__.__name__,
+            fields=', '.join(
+                '{0[0]}={0[1]}'.format(x) for x in sorted(attrs.items())
+            ),
+        )
+
+    def __str__(self):
+        return '{name} object'.format(name=self.__class__.__name__)
+
+    def __setattr__(self, name, value):
+        try:
+            return super(Base, self).__setattr__(name, value)
+        except ValidationError as error:
+            raise ValidationError(
+                "Error for field '{name}'.".format(name=name),
+                error
+            )
+
+    def __eq__(self, other):
+        if type(other) is not type(self):
+            return False
+
+        for name, _ in self.iterate_over_fields():
+            try:
+                our = getattr(self, name)
+            except errors.ValidationError:
+                our = None
+
+            try:
+                their = getattr(other, name)
+            except errors.ValidationError:
+                their = None
+
+            if our != their:
+                return False
+
+        return True
+
+    def __ne__(self, other):
+        return not (self == other)
+
+
+class _CacheKey(object):
+    """Object to identify model in memory."""
diff --git a/trains/backend_api/session/jsonmodels/parsers.py b/trains/backend_api/session/jsonmodels/parsers.py
new file mode 100644
index 00000000..b53641b2
--- /dev/null
+++ b/trains/backend_api/session/jsonmodels/parsers.py
@@ -0,0 +1,106 @@
+"""Parsers to change model structure into different ones."""
+import inspect
+
+from . import fields, builders, errors
+
+
+def to_struct(model):
+    """Cast instance of model to python structure.
+
+    :param model: Model to be casted.
+    :rtype: ``dict``
+
+    """
+    model.validate()
+
+    resp = {}
+    for _, name, field in model.iterate_with_name():
+        value = field.__get__(model)
+        if value is None:
+            continue
+
+        value = field.to_struct(value)
+        resp[name] = value
+    return resp
+
+
+def to_json_schema(cls):
+    """Generate JSON schema for given class.
+
+    :param cls: Class to be casted.
+    :rtype: ``dict``
+
+    """
+    builder = build_json_schema(cls)
+    return builder.build()
+
+
+def build_json_schema(value, parent_builder=None):
+    from .models import Base
+
+    cls = value if inspect.isclass(value) else value.__class__
+    if issubclass(cls, Base):
+        return build_json_schema_object(cls, parent_builder)
+    else:
+        return build_json_schema_primitive(cls, parent_builder)
+
+
+def build_json_schema_object(cls, parent_builder=None):
+    builder = builders.ObjectBuilder(cls, parent_builder)
+    if builder.count_type(builder.type) > 1:
+        return builder
+    for _, name, field in cls.iterate_with_name():
+        if isinstance(field, fields.EmbeddedField):
+            builder.add_field(name, field, _parse_embedded(field, builder))
+        elif isinstance(field, fields.ListField):
+            builder.add_field(name, field, _parse_list(field, builder))
+        else:
+            builder.add_field(
+                name, field, _create_primitive_field_schema(field))
+    return builder
+
+
+def _parse_list(field, parent_builder):
+    builder = builders.ListBuilder(
+        parent_builder, field.nullable, default=field._default)
+    for type in field.items_types:
+        builder.add_type_schema(build_json_schema(type, builder))
+    return builder
+
+
+def _parse_embedded(field, parent_builder):
+    builder = builders.EmbeddedBuilder(
+        parent_builder, field.nullable, default=field._default)
+    for type in field.types:
+        builder.add_type_schema(build_json_schema(type, builder))
+    return builder
+
+
+def build_json_schema_primitive(cls, parent_builder):
+    builder = builders.PrimitiveBuilder(cls, parent_builder)
+    return builder
+
+
+def _create_primitive_field_schema(field):
+    if isinstance(field, fields.StringField):
+        obj_type = 'string'
+    elif isinstance(field, fields.IntField):
+        obj_type = 'number'
+    elif isinstance(field, fields.FloatField):
+        obj_type = 'float'
+    elif isinstance(field, fields.BoolField):
+        obj_type = 'boolean'
+    else:
+        raise errors.FieldNotSupported(
+            'Field {field} is not supported!'.format(
+                field=type(field).__class__.__name__))
+
+    if field.nullable:
+        obj_type = [obj_type, 'null']
+
+    schema = {'type': obj_type}
+
+    if field.has_default:
+        schema["default"] = field._default
+
+    return schema
diff --git a/trains/backend_api/session/jsonmodels/utilities.py b/trains/backend_api/session/jsonmodels/utilities.py
new file mode 100644
index 00000000..59326fa1
--- /dev/null
+++ b/trains/backend_api/session/jsonmodels/utilities.py
@@ -0,0 +1,156 @@
+from __future__ import absolute_import
+
+import six
+import re
+from collections import namedtuple
+
+SCALAR_TYPES = tuple(list(six.string_types) + [int, float, bool])
+
+ECMA_TO_PYTHON_FLAGS = {
+    'i': re.I,
+    'm': re.M,
+}
+
+PYTHON_TO_ECMA_FLAGS = dict(
+    (value, key) for key, value in ECMA_TO_PYTHON_FLAGS.items()
+)
+
+PythonRegex = namedtuple('PythonRegex', ['regex', 'flags'])
+
+
+def _normalize_string_type(value):
+    if isinstance(value, six.string_types):
+        return six.text_type(value)
+    else:
+        return value
+
+
+def _compare_dicts(one, two):
+    if len(one) != len(two):
+        return False
+
+    for key, value in one.items():
+        if key not in one or key not in two:
+            return False
+
+        if not compare_schemas(one[key], two[key]):
+            return False
+    return True
+
+
+def _compare_lists(one, two):
+    if len(one) != len(two):
+        return False
+
+    they_match = False
+    for first_item in one:
+        for second_item in two:
+            if they_match:
+                continue
+            they_match = compare_schemas(first_item, second_item)
+    return they_match
+
+
+def _assert_same_types(one, two):
+    if not isinstance(one, type(two)) or not isinstance(two, type(one)):
+        raise RuntimeError('Types mismatch! "{type1}" and "{type2}".'.format(
+            type1=type(one).__name__, type2=type(two).__name__))
+
+
+def compare_schemas(one, two):
+    """Compare two structures that represents JSON schemas.
+
+    For comparison you can't use normal comparison, because in JSON schema
+    lists DO NOT keep order (and Python lists do), so this must be taken into
+    account during comparison.
+
+    Note this wont check all configurations, only first one that seems to
+    match, which can lead to wrong results.
+
+    :param one: First schema to compare.
+    :param two: Second schema to compare.
+    :rtype: `bool`
+
+    """
+    one = _normalize_string_type(one)
+    two = _normalize_string_type(two)
+
+    _assert_same_types(one, two)
+
+    if isinstance(one, list):
+        return _compare_lists(one, two)
+    elif isinstance(one, dict):
+        return _compare_dicts(one, two)
+    elif isinstance(one, SCALAR_TYPES):
+        return one == two
+    elif one is None:
+        return one is two
+    else:
+        raise RuntimeError('Not allowed type "{type}"'.format(
+            type=type(one).__name__))
+
+
+def is_ecma_regex(regex):
+    """Check if given regex is of type ECMA 262 or not.
+
+    :rtype: bool
+
+    """
+    parts = regex.split('/')
+
+    if len(parts) == 1:
+        return False
+
+    if len(parts) < 3:
+        raise ValueError('Given regex isn\'t ECMA regex nor Python regex.')
+    parts.pop()
+    parts.append('')
+
+    raw_regex = '/'.join(parts)
+    if raw_regex.startswith('/') and raw_regex.endswith('/'):
+        return True
+    return False
+
+
+def convert_ecma_regex_to_python(value):
+    """Convert ECMA 262 regex to Python tuple with regex and flags.
+
+    If given value is already Python regex it will be returned unchanged.
+
+    :param string value: ECMA regex.
+    :return: 2-tuple with `regex` and `flags`
+    :rtype: namedtuple
+
+    """
+    if not is_ecma_regex(value):
+        return PythonRegex(value, [])
+
+    parts = value.split('/')
+    flags = parts.pop()
+
+    try:
+        result_flags = [ECMA_TO_PYTHON_FLAGS[f] for f in flags]
+    except KeyError:
+        raise ValueError('Wrong flags "{}".'.format(flags))
+
+    return PythonRegex('/'.join(parts[1:]), result_flags)
+
+
+def convert_python_regex_to_ecma(value, flags=[]):
+    """Convert Python regex to ECMA 262 regex.
+
+    If given value is already ECMA regex it will be returned unchanged.
+
+    :param string value: Python regex.
+    :param list flags: List of flags (allowed flags: `re.I`, `re.M`)
+    :return: ECMA 262 regex
+    :rtype: str
+
+    """
+    if is_ecma_regex(value):
+        return value
+
+    result_flags = [PYTHON_TO_ECMA_FLAGS[f] for f in flags]
+    result_flags = ''.join(result_flags)
+
+    return '/{value}/{flags}'.format(value=value, flags=result_flags)
diff --git a/trains/backend_api/session/jsonmodels/validators.py b/trains/backend_api/session/jsonmodels/validators.py
new file mode 100644
index 00000000..ef9ff80c
--- /dev/null
+++ b/trains/backend_api/session/jsonmodels/validators.py
@@ -0,0 +1,202 @@
+"""Predefined validators."""
+import re
+
+from six.moves import reduce
+
+from .errors import ValidationError
+from . import utilities
+
+
+class Min(object):
+
+    """Validator for minimum value."""
+
+    def __init__(self, minimum_value, exclusive=False):
+        """Init.
+
+        :param minimum_value: Minimum value for validator.
+        :param bool exclusive: If `True`, then validated value must be strongly
+            lower than given threshold.
+
+        """
+        self.minimum_value = minimum_value
+        self.exclusive = exclusive
+
+    def validate(self, value):
+        """Validate value."""
+        if self.exclusive:
+            if value <= self.minimum_value:
+                tpl = "'{value}' is lower or equal than minimum ('{min}')."
+                raise ValidationError(
+                    tpl.format(value=value, min=self.minimum_value))
+        else:
+            if value < self.minimum_value:
+                raise ValidationError(
+                    "'{value}' is lower than minimum ('{min}').".format(
+                        value=value, min=self.minimum_value))
+
+    def modify_schema(self, field_schema):
+        """Modify field schema."""
+        field_schema['minimum'] = self.minimum_value
+        if self.exclusive:
+            field_schema['exclusiveMinimum'] = True
+
+
+class Max(object):
+
+    """Validator for maximum value."""
+
+    def __init__(self, maximum_value, exclusive=False):
+        """Init.
+
+        :param maximum_value: Maximum value for validator.
+        :param bool exclusive: If `True`, then validated value must be strongly
+            bigger than given threshold.
+
+        """
+        self.maximum_value = maximum_value
+        self.exclusive = exclusive
+
+    def validate(self, value):
+        """Validate value."""
+        if self.exclusive:
+            if value >= self.maximum_value:
+                tpl = "'{val}' is bigger or equal than maximum ('{max}')."
+                raise ValidationError(
+                    tpl.format(val=value, max=self.maximum_value))
+        else:
+            if value > self.maximum_value:
+                raise ValidationError(
+                    "'{value}' is bigger than maximum ('{max}').".format(
+                        value=value, max=self.maximum_value))
+
+    def modify_schema(self, field_schema):
+        """Modify field schema."""
+        field_schema['maximum'] = self.maximum_value
+        if self.exclusive:
+            field_schema['exclusiveMaximum'] = True
+
+
+class Regex(object):
+
+    """Validator for regular expressions."""
+
+    FLAGS = {
+        'ignorecase': re.I,
+        'multiline': re.M,
+    }
+
+    def __init__(self, pattern, **flags):
+        """Init.
+
+        Note, that if given pattern is ECMA regex, given flags will be
+        **completely ignored** and taken from given regex.
+
+
+        :param string pattern: Pattern of regex.
+        :param bool flags: Flags used for the regex matching.
+            Allowed flag names are in the `FLAGS` attribute. The flag value
+            does not matter as long as it evaluates to True.
+            Flags with False values will be ignored.
+            Invalid flags will be ignored.
+
+        """
+        if utilities.is_ecma_regex(pattern):
+            result = utilities.convert_ecma_regex_to_python(pattern)
+            self.pattern, self.flags = result
+        else:
+            self.pattern = pattern
+            self.flags = [self.FLAGS[key] for key, value in flags.items()
+                          if key in self.FLAGS and value]
+
+    def validate(self, value):
+        """Validate value."""
+        flags = self._calculate_flags()
+
+        try:
+            result = re.search(self.pattern, value, flags)
+        except TypeError as te:
+            raise ValidationError(*te.args)
+
+        if not result:
+            raise ValidationError(
+                'Value "{value}" did not match pattern "{pattern}".'.format(
+                    value=value, pattern=self.pattern
+                ))
+
+    def _calculate_flags(self):
+        return reduce(lambda x, y: x | y, self.flags, 0)
+
+    def modify_schema(self, field_schema):
+        """Modify field schema."""
+        field_schema['pattern'] = utilities.convert_python_regex_to_ecma(
+            self.pattern, self.flags)
+
+
+class Length(object):
+
+    """Validator for length."""
+
+    def __init__(self, minimum_value=None, maximum_value=None):
+        """Init.
+
+        Note that if no `minimum_value` neither `maximum_value` will be
+        specified, `ValueError` will be raised.
+
+        :param int minimum_value: Minimum value (optional).
+        :param int maximum_value: Maximum value (optional).
+
+        """
+        if minimum_value is None and maximum_value is None:
+            raise ValueError(
+                "Either 'minimum_value' or 'maximum_value' must be specified.")
+
+        self.minimum_value = minimum_value
+        self.maximum_value = maximum_value
+
+    def validate(self, value):
+        """Validate value."""
+        len_ = len(value)
+
+        if self.minimum_value is not None and len_ < self.minimum_value:
+            tpl = "Value '{val}' length is lower than allowed minimum '{min}'."
+            raise ValidationError(tpl.format(
+                val=value, min=self.minimum_value
+            ))
+
+        if self.maximum_value is not None and len_ > self.maximum_value:
+            raise ValidationError(
+                "Value '{val}' length is bigger than "
+                "allowed maximum '{max}'.".format(
+                    val=value,
+                    max=self.maximum_value,
+                ))
+
+    def modify_schema(self, field_schema):
+        """Modify field schema."""
+        if self.minimum_value:
+            field_schema['minLength'] = self.minimum_value
+
+        if self.maximum_value:
+            field_schema['maxLength'] = self.maximum_value
+
+
+class Enum(object):
+
+    """Validator for enums."""
+
+    def __init__(self, *choices):
+        """Init.
+
+        :param [] choices: Valid choices for the field.
+        """
+
+        self.choices = list(choices)
+
+    def validate(self, value):
+        if value not in self.choices:
+            tpl = "Value '{val}' is not a valid choice."
+            raise ValidationError(tpl.format(val=value))
+
+    def modify_schema(self, field_schema):
+        field_schema['enum'] = self.choices
diff --git a/trains/backend_api/session/response.py b/trains/backend_api/session/response.py
index 0cc6787e..9025354a 100644
--- a/trains/backend_api/session/response.py
+++ b/trains/backend_api/session/response.py
@@ -1,10 +1,8 @@
 import requests
 
 import six
-import jsonmodels.models
-import jsonmodels.fields
-import jsonmodels.errors
 
+from . import jsonmodels
 from .apimodel import ApiModel
 from .datamodel import NonStrictDataModelMixin