semantic execution meets geospatial web services: a pilot application

Copyright 2008 Digital Enterprise Research Institute. All rights reserved.

Digital Enterprise Research Institute www.deri.ie

Semantic Execution Meets Geospatial Web Services:

A Pilot Application

Raluca Zaharia, Laurentiu Vasiliu (DERI)Joerg Hoffman (SAP Research) Eva Klien (Fraunhofer Institute)

Terra Cognita 2008,

Oct. 26, Karlsruhe,

Germany

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Overview

Motivation Scenario Semantic model Execution Results Conclusions

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Motivation

Why semantics and geospatial web services:

data sharing and processing functionalities for geospatial entities

not just one service metadata standards and catalogue services for

description and search of geospatial services no specifications to formally and explicitly define

semantics of the data and functionality

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Motivation

We want automation Discovery Interoperability Integration

A semantic framework (WSMO/L/X) semantic descriptions modelled unsatisfactory execution performance

complex scenario large amount of data

of geospatial services

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Scenario

DepartmentsDepartments

ConsumptionConsumption

Production-Consumption

Map data

Production-Consumption

Map data

QuarriesQuarries

PopulationPopulation ConsumptionConsumption

ProductionProduction

Average consumption

Average consumption

PopulationPopulation

ProductionProductionQuarriesQuarries(lat, long)

(lat, long)

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Mediators

Semantic Model

OntologiesOntologies

GoalsGoals Web servicesWeb services

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Modeling tools

WSMT v1.4.1 CompositionS

tudio

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Execution

Co

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an

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Pa

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ars

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Dis

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isc

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ery

Da

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iati

on

Da

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ed

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on

Ch

ore

og

rap

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ine

Ch

ore

og

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ng

ine

Inv

ok

er

Inv

ok

er

CoreCore

Resource Manager

Resource Manager

WSMO2Reasoner Framework

WSMO2Reasoner Framework

WSMX

AdminWFSAdminWFS

QuarriesWFSQuarriesWFS

PassthroughPassthrough

Geospatial Web

Services

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Execution

WSMX Execution Semantics

WSMX Choreography

Engine

Requester Choreography

Provider Choreography

WSMX Invoker component

registerChoreography (goal) initialize (state signature, choreography rules)

registerChoreography (WS) initialize (state signature, choreography rules)

updateState (R-to-P, instances) update (instances)

step

instances to send

instances to send > 0

invokeWS (instance to send)

service response ontology

create response ontology

updateState (P-to-R, instances) update (instances)

step

isProviderChorInEndState()

in Choreography Execution

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Improving the performance

Generality vs. performance

Minimum number of steps Minimum number of instances in the state

ontology -> call services early -> eliminate redundant calls -> cache reasoning results

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Results

Surface sizeWeb services

(Total duration)

Instancesin the state

ontology

Currentimplementation

with reasoning tool

KAON2 IRIS

1 department 7 WS (3.84s) 164 88.57s 25.43s

2 departments 12 WS (5.03s) 321 184.5s 41.48s

3 departments 17 WS (6.89s) 430 314.37s 55.78s

15 department

s

77 WS (33.89s) 2082 4531.20s 492.41s

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Conclusions

Real-life scenario of semantic execution in the geospatial domain

Why use semantics (the framework supports): Semantically described elements are a lot easier

to (re)use Reduced implementation time Increased agility N:M integration

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Conclusions

Degree of automation Services ranked and selected accurately Compositions more adaptable to changes

User input/approval still required.

Automatic composition not available(lack of semantic descriptions, tools for users etc.)

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Conclusions

Support for creation and execution of complex and flexible compositions

Service requester and service provider completely decoupled

An approach for generating the composition rules can used on top of the existing framework

ASM: simple and intuitive way of defining service compositions

“describe the requirements rather than telling the system step by step what to do”

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Conclusions

Each domain has particular requirements => discovery, mediation, execution etc. stressed in

a different way

SWS techniques over real services from the geospatial domain => huge execution overhead introduced

Significant advantages of the approach => mandatory to improve the framework performance.

semantic execution meets geospatial web services: a pilot application

Documents

execution of complex

geospatial entitiesnot

catalogue services

real services

state ontology

framework performance

data sharing

decoupledan approach