Summer SOCJuly 2nd – July 7th

Aniketos platform:Design of a trustworthy composite

service

1

Summer SOC 2012

A service provider wants to offer a service that takes in input the geographical position of a user and shows in a webpage a set of information: A map showing the position Weather information Point of interests in the surroundings

The service provider wants the service to be trustworthy, so he asks the service designer to exploit the tools made available through the Aniketos platform

2

Reference scenario for the demo

Summer SOC 2012

The trustworthiness value is evaluated by the Trustworthiness Prediction module and is a combination of: Cognitive trust of the user, based on the service and service

provider reputation. Non-cognitive trust, based on objective and measurable properties

of the service such as QoS attributes (reliability, performance, availability)

3

About trustworthiness in Aniketos…

Summer SOC 20124

Service Composition Framework (SCF)

The SCF is a design time module available in the Aniketos environment allowing a service designer to build executable composition plans

To use the framework the service designer must be authenticated

Summer SOC 20125

SCF: get started with BPMN modelling

Once authenticated, the service designer can start the BPMN modelling

Summer SOC 20126

BPMN model of InfoService

From the description of the service in terms of functionality, the service designer decides to use different atomic services and compose them according to the BPMN drafted in the SCF editor

Summer SOC 2012

The service designer is in charge of designing a composite service with a specific requirement on trusthworthiness value

The trustworthiness requirement is expressed as a consumer policy written in ConSpec grammar

The file location is included in an extensionElements tag in the xml representing the BPMN

7

BMPN annotated with trustworthiness requirement

Summer SOC 2012

An excerpt of the resulting xml for the annotated BPMN is shown below:

8

Annotated BPMN

Summer SOC 2012

To make the composition plans the SCF has to bind real web services to the service tasks in the BPMN

The binding process entails: Service discovery using the ServiceType as search filter

The SCF shows the operations offered by the web services matching the request based on the ServiceType

Selection of the specific operation the service designer wants to use in order to compose the InfoService

If the same operation is offered by different atomic services the service designer will see just one operation

9

Service discovery and selection of the service operation

Summer SOC 201210

Discovery and selection: GeoCoding example (1/2)

Summer SOC 2012

and selects getCoordinates ( )

11

Discovery and selection: GeoCoding example (2/2)

The service designer discovers operations offered by GeoCoding type services ( )

1

2

The service designer isn’t aware of how many web services offer that operation, it’s the SCF which will bind the different services to the service task when making composition plans

Summer SOC 2012

Creation of composition plans

12

Once the service designer has selected an operation for each service task the SCF is ready to create the composition plans

When the service designer clicks on “Create composition plans” button, the SCF shows a set of functionally valid composition plans

Summer SOC 2012

The SCF has created 12 composition plans: this is explained by the number of web

services offering the same operation: Geocoding type: bound to 2 web services PointOfInterest type: bound to 3 web services WeatherForecast type: bound to 1 web

services Map type: bound to 2 web services WebPageInfoCollector type: bound to 1 web

services

Thus the number of composition plans is 2 X 3 X 1 X 2 X 1 = 12

13

Composition plans created by the SCF

Summer SOC 2012

The composition plans ensure functionality but do not consider the trustworthiness requirement

The composition plans have to be checked against the requirements specified for the trustworthiness value

This check is performed by the Secure Composition Planner Module which receives the composition plans from the SCF and returns those ones that fulfill the trustworthiness requirement

14

Selection of trustworthy composition plans

Summer SOC 2012

The SCPM invokes the Trustworthiness prediction module to evaluate the trustworthiness value for the set of composition plans received from the SCF

The trustworthiness value of the composite service is evaluated using the weakest link principle The Trustworthiness module evaluates the trustworthiness value

for each service taking part in the composition The lowest value is returned as the trustworthiness value of the

composite service

15

Trustworthiness prediction for composite services

Summer SOC 2012

When the service designer clicks on “Verify All” button the SCPM selects the composition plans that fulfils the trustworthiness requirement

16

Trustworthy composite services

In order to visualize the Trustworthiness value of the composition plans the service designer selects “Order By” Trustworthiness and clicks on “Order/Rank” button

Summer SOC 201217

Last steps: upload and deploy

The service designer selects one of the trustworthy composition plans and can Upload the BPMN to an Activiti

Engine Deploy it to a web application

server

Summer SOC 201218