Event Management Proposal for Distribution Data Service Standard

10th International Symposium on Distributed Computing and Artificial IntelligenceSalamanca, 22nd-24th May, 2013

Event Management Proposal for Distribution Data Service StandardJosé-Luis Poza-LujánJuan-Luis Posadas-YagüeJosé-Enrique Simó-TenUniversity Institute of Control Systems and Industrial Computing (ai2)Universitat Politècnica de València (UPV).

···

Events

···

Actions

···

···

···

···

···

···

···

Conditions

Component Operations

QoS Alarms

QoC Alarms

Message Filters

Component Functions

QoS Configuration

QoC Configuration

Message Filtering

Event

-m_iState-m_iType-m_pCondition

+setState()+getState()+getType()

EventAlarm

-m_iAlarmType-m_iAlarmValue-m_iStartupAlarm-m_iThersholdRising-m_iThersholdFalling

EventFilter

-m_iOffset-m_sPattern-m_sMask-m_bSendEvent-m_bDeleteMessage-m_bCloseQueue

Entity

-m_pListOfConditions

+onCondition()+addCondition()+removeCondition()

Condition

-m_iState-m_pListOfEvents-m_pEntity-m_iPriority

+setState()+getState()+onEvent()

EventComponent

-m_iEventComponentType


Contextualization

DDS Model

Event management proposal

Implementation

Experiment and results

Conclusions and future work

NCS, EBC and Middleware• Event-Based Control (EBC) paradigm

(also called event-driven control) is adopted to implement systems where…– The periodic sampling is not possible.– The periodic sampling is not recommended

• In networked control systems (NCS), distributed control elements are connected by a network.– Control elements needs to know the

technology– Problems with synchronization


Contextualization

DDS Model


Implementation



NCS, EBC and Middleware• A middleware enhances and offers to

control elements a set of services in order to facilitate the access to the network. – If EBC is used in NCS, the middleware will be

an essential component.• Middleware architecture is based on

communications paradigms.– Message passing– Client-server– Publish/Subscribe (P/S)– Blackboard.


Contextualization

DDS Model


Implementation



DDS Model• Data Distribution Service for Real-Time

Systems (DDS) is an OMG standard middleware based on the P/S paradigm.– Offers time-controlled communications

between components using Quality of Service (QoS) polices.

Do

mai

n P

arti

cip

ant

write read, takeon_data_available

Producer Consumer

Data Writer

Data Writer

Publ

ishe

r

Data Reader

Listener

Subs

crib

er

Topic

Data Writer

Data Reader

Subs

crib

er

Publ

ishe

r

Data Reader

Topic

Topic

Do

mai

n P

arti

cip

ant

Do

mai

n P

arti

cip

ant

read, take write

ConsumerProducer & Consumer

Consumer

read, take


Contextualization

DDS Model


Implementation



DDS Model• DDS can be used to send any kind of

Data, including event data. • DDS allows the application (control

component in NCS) to perform flexible filtering of events.

Entity

StatusCondition

1

0..1statuscondition

ConditionWaitSet* *

GuardCondition ReadCondition


Contextualization

DDS Model


Implementation



DDS Model• DDS can be used to send any kind of

Data, including event data. • DDS allows the application (control

component in NCS) to perform flexible filtering of events.

• NCS needs certain event management,

But DDS does not define a built-in event type and advanced event management.


Contextualization

DDS Model


Implementation



Event management proposal• DDS offers adequate support to

coordinate communications between nodes, but it does not provide a mechanism to review the internal characteristics.

• To extend the capacity of DDS, a new component, called Action, is added.

• The role of Condition and Waitset components has been increased.


Contextualization

DDS Model


Implementation



Event management proposal• Main components are “Events”,

“Conditions” and “Actions”

···

Events

···

Actions

···

···

···

···

···

···

···

Conditions


QoS Alarms

QoC Alarms

Message Filters

Component Functions

QoS Configuration

QoC Configuration

Message Filtering


Contextualization

DDS Model


Implementation



Event management proposal• In our proposal Condition is similar to

WaitSet DDS element, Event is similar to Condition and Action is the new element

Entity

1

*condList

Event

EventAlarm EventFilterEventComponent

ConditioneventList

*

Action1 *

*actList


Contextualization

DDS Model


Implementation



Implementation• A distributed mobile robot navigation

environment has been used to test the validity and usefulness of the proposed model.

• The mobile robot is controlled by a set of control algorithms.– Reactive behaviours algorithms, are embedded

within the robot.– The deliberative algorithms, are implemented in

distributed nodes• In the experiment, all algorithms are

implemented in distributed nodes


Contextualization

DDS Model


Implementation



Implementation• The algorithm used is the “obstacle

avoidance” based on Braitenberg vehicles behaviours.

Mleft Mright

S0

S1

S2 S3

S4

S5

S6S7


Contextualization

DDS Model


Implementation



Implementation• Obstacle avoidance algorithm

1. Sensor detects obstacle and sends the distance to control node with a specified period

2. Control node changes the robot speed and path in function of the distance detected by all sensors in the ring using the formula to each motor


Contextualization

DDS Model


Implementation



Implementation• Optimization with event management

– The DDS based middleware filters sensor messages and only sends significant messages. The time interval between messages can change the robot speed by means the formula


Contextualization

DDS Model


Implementation



Experiment and results• Two scenarios have been tested

a) Robot in corridorb) Wall in front of robot

• Event Management influence1) Robot navigation without middleware event

detection 2) The same navigation with event detection and one

Action linked by means a Condition

Scenarios(1) DDS (2) DDS Event

ManagementSamplingPeriod

DistanceAverage

SamplingPeriod

DistanceAverage

(a) Robot in corridor 10.0 2.1 62.6 2.1

(b) Wall in front of robot 10.0 1.1 9.4 0.6


Contextualization

DDS Model


Implementation



a) Robot in corridor– No significant

differences in distance– Message load

optimization

b) Wall in front of robot– Significant differences

in distance (speed optimization)

– Message load optimization



Contextualization

DDS Model


Implementation



Conclusions and future work• Proposal to increase the event management

system proposed in the DDS standard• The most significant contribution is the

inclusion of a new object called Action.– Actions automatically make changes on the

middleware based on a combination of events.• The Action object has been tested with a

simple mobile robot system. • Future work

– Test the middleware with complex event combinations to generate different actions.

– Use priorities in Conditions or in Actions.


Thanks for your attention

···

Events

···

Actions

···

···

···

···

···

···

···

Conditions


QoS Alarms

QoC Alarms

Message Filters

Component Functions

QoS Configuration

QoC Configuration

Message Filtering

Event

-m_iState-m_iType-m_pCondition

+setState()+getState()+getType()

EventAlarm

-m_iAlarmType-m_iAlarmValue-m_iStartupAlarm-m_iThersholdRising-m_iThersholdFalling

EventFilter

-m_iOffset-m_sPattern-m_sMask-m_bSendEvent-m_bDeleteMessage-m_bCloseQueue

Entity

-m_pListOfConditions

+onCondition()+addCondition()+removeCondition()

Condition

-m_iState-m_pListOfEvents-m_pEntity-m_iPriority

+setState()+getState()+onEvent()

EventComponent

-m_iEventComponentType

The study described in this paper is a part of the coordinated project COBAMI: Mission-based Hierarchical Control. Education and Science Department, Spanish Government. CICYT: MICINN: DPI2011-28507-C02-01/02

Technology

Event Management Proposal for Distribution Data Service Standard