The Specs Package

The Interface Spec Module

This module implements the Capability Interface concept

This module contains free functions which serve as factories for the CapabilityInterface class. These factories can take the spec file for a Capability Interface and create a CapabilityInterface instance out of it. The Interface class encapsulates the interface itself, representing the topics, services, params, etc... The CapabilityInterface class encapsulates meta information about the Interface like the name, description, and extends the Interface class. The Interface class is made up of InterfaceElement‘s which represent the elements of a Capability Interface, each consisting of a name, type, and description.

With an Interface RGBCamera.yaml, like this:

%YAML 1.1
# Capability Interface file for RGBCamera
---
# Name of the Interface
name: RGBCamera
spec_version: 1
spec_type: interface
description: 'This Capability describes the interface exposed by a generic RGBCamera.'
interface:
  # Topics
  topics:
    # Topics provided by the interface
    provides:
      'camera/image_raw':
        type: 'sensor_msgs/Image'
        description: 'raw image from the camera'
      'camera/camera_info':
        type: 'sensor_msgs/CameraInfo'
    # Topics expect by the interface
    requires: {}
  # Services provided by the interface
  services:
    'camera/set_info':
      type: 'sensor_msgs/SetCameraInfo'

You can use this interface like so:

>>> from pprint import pprint
>>> from capabilities.specs.interface import capability_interface_from_file_path
>>> ci = capability_interface_from_file_path('test/unit/specs/interfaces/RGBCamera.yaml')
>>> pprint(ci.topics)
{'camera/camera_info': <capabilities.specs.interface.InterfaceElement object at 0x10736ced0>,
 'camera/image_raw': <capabilities.specs.interface.InterfaceElement object at 0x10736cf10>}
>>> print(ci.topics.values()[0].name)
camera/image_raw
>>> print(ci.topics.values()[0].type)
sensor_msgs/Image
>>> print(ci.topics.values()[0].description)
raw image from the camera
>>> pprint(ci.required_services)
{}
>>> pprint(ci.provided_topics)
{'camera/camera_info': <capabilities.specs.interface.InterfaceElement object at 0x10774ce10>,
 'camera/image_raw': <capabilities.specs.interface.InterfaceElement object at 0x10774ce50>}
>>> pprint(ci.actions)
{}

class capabilities.specs.interface.CapabilityInterface(name, spec_version, description=None)

Represents a Capability Interface

A Capability Interface is defined by:

• name (str): name of the interface
• spec_type (str): type of the interface specification (has to be ‘interface’)
• spec_version (int): version of the interface specification
• description (str): free form description of the interface
• default_provider (str): name of the default provider for this interface, defaults to ‘unknown’
• interface (Interface): representation of components which make up the interface

class capabilities.specs.interface.Interface

Represents the Interface part of a Capability Interface

An Interface can consist of zero to all of these elements:

• topics: (name/type)
  • requires: Expected topics
  • provides: Provided topics
• services: (name/type)
  • requires: Expected services
  • provides: Provided services
• actions: (name/type)
  • requires: Expected actions
  • provides: Provided actions
• parameters: (name/type/description)
  • requires: Parameters which should be set for the interface, e.g. map_resolution
  • provides: Parameters which the interface provides, e.g. robot_model
• dynamic_parameters: List of dynamic_parameters which are available (name)

The groupings ‘requires’ and ‘provides’ are purely semantic, and are not used by the capability system programatically, but instead are there to give more meaning to the developers.

add_action(action_name, interface_element, grouping=None)

Adds a action to the Interface

Parameters:

• action_name (str) – name of the action
• interface_element (InterfaceElement) – InterfaceElement instance for the action
• grouping (str or None) – semantic grouping of the action, ‘requires’, ‘provides’, or None

Raises:

ValueError if the grouping is invalid

Raises:

RuntimeError if the action is already in the interface

add_dynamic_parameter(dynamic_parameter_name)

Adds a dynamic_parameter to the Interface

Parameters:dynamic_parameter_name (str) – name of the dynamic_parameter Raises:RuntimeError if the dynamic_parameter is already in the interface

add_parameter(parameter_name, interface_element, grouping=None)

Adds a parameter to the Interface

Parameters:

• parameter_name (str) – name of the parameter
• interface_element (InterfaceElement) – InterfaceElement instance for the parameter
• grouping (str or None) – semantic grouping of the parameter, ‘requires’, ‘provides’, or None

Raises:

ValueError if the grouping is invalid

Raises:

RuntimeError if the parameter is already in the interface

add_service(service_name, interface_element, grouping=None)

Adds a service to the Interface

Parameters:

• service_name (str) – name of the service
• interface_element (InterfaceElement) – InterfaceElement instance for the service
• grouping (str or None) – semantic grouping of the service, ‘requires’, ‘provides’, or None

Raises:

ValueError if the grouping is invalid

Raises:

RuntimeError if the service is already in the interface

add_topic(topic_name, interface_element, grouping=None)

Adds a topic to the Interface

Parameters:

• topic_name (str) – name of the topic
• interface_element (InterfaceElement) – InterfaceElement instance for the topic
• grouping (str or None) – semantic grouping of the topic, ‘requires’, ‘provides’, or None

Raises:

ValueError if the grouping is invalid

Raises:

RuntimeError if the topic is already in the interface

class capabilities.specs.interface.InterfaceElement(name, element_kind, element_type=None, description=None)

Represents a part of an interface

An interface element is defined by:

• name: topic, service, action, or parameter name
• element kind: topic, service, action, parameter, or dynamic_parameter
• type: topic, service or action type (pkg/msg) or parameter type
• description: free form description of the element

Raises:ValueError if the element kind is invalid

exception capabilities.specs.interface.InvalidInterface(msg, file_name)

InvalidInterface exception

capabilities.specs.interface.capability_interface_from_dict(spec, file_name='<dict>')

Creates a CapabilityInterface instance from a dict version of the spec

Parameters:

• string (dict) – Capability Interface spec
• file_name – Name of the file where this spec originated (defaults to ‘<dict>’)
• file_name – str

Returns:

CapabilityInterface instance, populated with the provided spec

Return type:

CapabilityInterface

Raises:

InvalidInterface if the spec is not complete or has invalid entries

capabilities.specs.interface.capability_interface_from_file(file_handle)

Creates a CapabilityInterface instance from a given spec file handle

See capability_interface_from_dict() for list of possible exceptions

Parameters:file_handle (file) – file handle for the Capability Interface spec file Returns:CapabilityInterface instance, populated with data from the spec file Return type:CapabilityInterface Raises:OSError if the given file does not exist

capabilities.specs.interface.capability_interface_from_file_path(file_path)

Creates a CapabilityInterface instance from a spec file at a given path

See capability_interface_from_dict() for list of possible exceptions

Parameters:file_path (str) – location of the Capability Interface spec file Returns:CapabilityInterface instance, populated with data from the spec file Return type:CapabilityInterface Raises:OSError if the given file does not exist

capabilities.specs.interface.capability_interface_from_string(string, file_name='<string>')

Creates a CapabilityInterface instance from a string containing the spec

See capability_interface_from_dict() for list of possible exceptions

Parameters:

• string (str) – Capability Interface spec
• file_name – Name of the file where this spec originated (defaults to ‘<string>’)
• file_name – str

Returns:

CapabilityInterface instance, populated with the provided spec

Return type:

CapabilityInterface

Raises:

AttributeError if the given value for string is not a str

The Provider Spec Module

This module implements the Capability Provider concept

This module contains free functions which serve as factories for the CapabilityProvider class. These factories can take the spec file for a Capability Provider and create a CapabilityProvider instance out of it. The CapabilityProvider class is designed to encapsualte the meta data which describes the Capability Provider.

With a provider spec like this:

%YAML 1.1
---
name: navigation_nav_stack
spec_version: 1
spec_type: provider
description: 'Implements the ability to navigate.'
implements: navigation/Navigation
launch_file: 'launch/navigation_nav_stack.launch'
depends_on:
    'laser_capability/LaserObservation':
        provider: 'hokuyo_capability/hokuyo_base'
remappings:
    topics:
        'scan': 'nav_stack/scan'
nodelet_manager: 'nav_manager'

You can use this API like this:

>>> from pprint import pprint
>>> from capabilities.specs.provider import capability_provider_from_file_path
>>> cp = capability_provider_from_file_path('test/unit/specs/providers/navigation_nav_stack.yaml')
>>> pprint(cp.dependencies)
{<capabilities.specs.common.SpecName object at 0x1099ebfd0>:
    <capabilities.specs.provider.DependsOnRelationship object at 0x109a3fa50>}
>>> print(cp.dependencies['laser_capability/LaserObservation'])
laser_capability/LaserObservation:
    preferred provider: hokuyo_capability/hokuyo_base
>>> print(cp.launch_file)
launch/navigation_nav_stack.launch
>>> print(cp.implements)
navigation/Navigation
>>> print(cp.nodelet_manager)
nav_manager

class capabilities.specs.provider.CapabilityProvider(name, spec_version, implements, launch_file=None, description=None, remappings=None, nodelet_manager=None)

Represents a Capability Provider

A Capability Provider is defined by:

• name (str): name of the provider
• spec_type (str): type of the specification (has to be ‘provider’)
• spec_version (int): version of the provider specification
• description (str): free form description of the provider
• implements (str): Name of a Capability Interface which this provider implements
• launch_file (str or None): Path to a launch file which runs the provider, None indicates no launch file to run
• depends_on (dict): list of depends on relationships to Capabilities with remappings and provider preference
• remappings (dict): map of ROS Names defined in the Capability to their new names for this provider
• nodelet_manager (str or None): name of the nodelet manager used by the provider, this is an implementation hint

class capabilities.specs.provider.DependsOnRelationship(capability_name, preferred_provider)

Models the depends_on relationship between a Capability Provider and a Capability

This relationship consists of:

• capability_name (str): name of the Capability which is depended on
• provider_preference (str): (optional) name of preferred provider for the Capability which is depended on

exception capabilities.specs.provider.InvalidProvider(msg, file_name)

InvalidProvider exception

capabilities.specs.provider.capability_provider_from_dict(spec, file_name='<dict>')

Creates a CapabilityProvider instance from a dict version of the spec

Parameters:

• string (dict) – Capability Provider spec
• file_name (str) – Name of the file where this spec originated (defaults to ‘<dict>’)

Returns:

CapabilityProvider instance, populated with the provided spec

Return type:

CapabilityProvider

Raises:

InvalidProvider if the spec is not complete or has invalid entries

capabilities.specs.provider.capability_provider_from_file(file_handle)

Creates a CapabilityProvider instance from a given spec file handle

See capability_provider_from_dict() for list of possible exceptions

Parameters:file_handle (file) – file handle for the Capability Provider spec file Returns:CapabilityProvider instance, populated with data from the spec file Return type:CapabilityProvider Raises:OSError if the given file does not exist

capabilities.specs.provider.capability_provider_from_file_path(file_path)

Creates a CapabilityProvider instance from a spec file at a given path

See capability_provider_from_dict() for list of possible exceptions

Parameters:file_path (str) – location of the Capability Provider spec file Returns:CapabilityProvider instance, populated with data from the spec file Return type:CapabilityProvider Raises:OSError if the given file does not exist

capabilities.specs.provider.capability_provider_from_string(string, file_name='<string>')

Creates a CapabilityProvider instance from a string containing the spec

See capability_provider_from_dict() for list of possible exceptions

Parameters:

• string (str) – Capability Provider spec
• file_name (str) – Name of the file where this spec originated (defaults to ‘<string>’)

Returns:

CapabilityProvider instance, populated with the provided spec

Return type:

CapabilityProvider

Raises:

AttributeError if the given value for string is not a str

The Semantic Interface Spec Module

This module implements the Semantic Capability Interface concept

This module contains free functions which serve as factories for the SemanticCapabilityInterface class. These factories can take the spec file for a Semantic Capability Interface and create a SemanticCapabilityInterface instance out of it. The SemanticCapabilityInterface class encapsulates meta information about the semantic interface. The SemanticCapabilityInterface class defines of:

• A capability which is being redefined, by name and remappings
• A name
• A global namespace (optional)
• Any ROS Name remappings (optional)

With an Semantic Capability Interface FrontRGBCamera.yaml, like this:

%YAML 1.1
---
name: FrontRGBCamera
spec_version: 1
spec_type: semantic_interface
description: 'This is semantically the Front RGB camera.'
redefines: 'a_package/RGBCamera'
# First the global_namespace is applied to all ROS Names
global_namespace: 'front_camera'
# Then individual remappings are done, and override the global_namespace
remappings:
  topics:
    'camera/image_raw': 'front_camera/image_raw'
    'camera/camera_info': 'front_camera/camera_info'
  services:
    'camera/set_info': 'front_camera/set_info'

You can use this interface like so:

>>> from pprint import pprint
>>> from capabilities.specs.semantic_interface import semantic_capability_interface_from_file_path
>>> sci = semantic_capability_interface_from_file_path('test/specs/semantic_interfaces/FrontRGBCamera.yaml')
>>> print(sci.redefines)
a_package/RGBCamera
>>> print(sci.global_namespace)
front_camera
>>> pprint(sci.remappings)
{'camera/camera_info': 'front_camera/camera_info',
 'camera/image_raw': 'front_camera/image_raw',
 'camera/set_info': 'front_camera/set_info'}

exception capabilities.specs.semantic_interface.InvalidSemanticInterface(msg, file_name)

InvalidSemanticInterface exception

class capabilities.specs.semantic_interface.SemanticCapabilityInterface(name, redefines, spec_version, description=None, global_namespace=None)

Represents a Semantic Capability Interface

A Semantic Capability Interface is defined by:

• name (str): name of the redefined interface
• redefines (str): name of a capability being redefined
• spec_type (str): type of the interface specification (has to be ‘semantic_interface’)
• spec_version (int): version of the interface specification
• description (str): free form description of the interface
• global_namespace (str or None): (optional) global namespace for all ROS Names, None means no global_namespace
• remappings (dict): (optional) map from ROS Names in redefined interface to Names in this interface

capabilities.specs.semantic_interface.semantic_capability_interface_from_dict(spec, file_name='<dict>')

Creates a SemanticCapabilityInterface instance from a dict version of the spec

Parameters:

• string (dict) – Semantic Capability Interface spec
• file_name (str) – Name of the file where this spec originated (defaults to ‘<dict>’)

Returns:

SemanticCapabilityInterface instance, populated with the provided spec

Return type:

SemanticCapabilityInterface

Raises:

InvalidSemanticInterface if the spec is not complete or has invalid entries

capabilities.specs.semantic_interface.semantic_capability_interface_from_file(file_handle)

Creates a SemanticCapabilityInterface instance from a given spec file handle

See semantic_capability_interface_from_dict() for list of possible exceptions

Parameters:file_handle (file) – file handle for the Semantic Capability Interface spec file Returns:SemanticCapabilityInterface instance, populated with data from the spec file Return type:SemanticCapabilityInterface Raises:OSError if the given file does not exist

capabilities.specs.semantic_interface.semantic_capability_interface_from_file_path(file_path)

Creates a SemanticCapabilityInterface instance from a spec file at a given path

See semantic_capability_interface_from_dict() for list of possible exceptions

Parameters:file_path (str) – location of the Semantic Capability Interface spec file Returns:SemanticCapabilityInterface instance, populated with data from the spec file Return type:SemanticCapabilityInterface Raises:OSError if the given file does not exist

capabilities.specs.semantic_interface.semantic_capability_interface_from_string(string, file_name='<string>')

Creates a SemanticCapabilityInterface instance from a string containing the spec

See semantic_capability_interface_from_dict() for list of possible exceptions

Parameters:

• string (str) – Semantic Capability Interface spec
• file_name (str) – Name of the file where this spec originated (defaults to ‘<string>’)

Returns:

SemanticCapabilityInterface instance, populated with the provided spec

Return type:

SemanticCapabilityInterface

Raises:

AttributeError if the given value for string is not a str