Services, Semantics and Linked Data

John DomingueKnowledge Media Institute, The Open University & STI International

Agenda• Software and Services• A Short History of Semantic Web Services • Linked Data Effect• Rise of REST• Linked Data and Services• Example Applications• Current and Future W3C work• Summary

SOFTWARE AND SERVICES

Software• Slow to produce!

–10 lines of code per day

• Code is ubiquitous –Car has 2 million lines of code

(8,000 Person Years)–Windows XP 45 million lines of code

(180,000 Person Years)

• Reusability is important

Service (economic)• Intangible commodity

–Consulting, childcare, educational• Tertiary sector of the economy

–Provision of value-adding services –Complementing

• secondary sector manufacturing and• primary sector: agriculture, fishing, mining …

–63% of Global GDP $44 trillion

Service (computational)

Web Service Usage Process• Deployment

– create and publish Web service description• Discovery

– determine usable services for a task• Composition

– combine services to achieve a goal• Selection

– choose most appropriate service• Mediation

– solve mismatches (data, protocol, process) that hamper interoperation

• Execution– invoke Web services following programmatic conventions

Web Service Execution Support• Monitoring

– control the execution process

• Compensation– provide transactional support and undo

or mitigate unwanted effects

• Replacement– facilitate the substitution of services by

equivalent ones

• Auditing– verify that service execution occurred in

the expected way

WSDL

WSDL Simplified

Web service

Operation 1

Operation 2

Operation N

input

input

input

output

output

output

...+-

A SHORT HISTORY OF SEMANTIC WEB SERVICES

OWL-S

Ontology images compliments of Terry Payne, University of Southampton

Service Profile (partial)

Class Hierarchies of ServicesServiceProfile

ProductProvidingService

Manufacturing

Transportation

ActionService

InfoService

PhysicalProductService Repair

information-Product+

physicalProduct+manufacturer+

deliveryRegion*deliveryProvider*

deliveryType

physical-Product+

transportationMode+geographicRegion+

physicalProduct+

Tie in with UNSPSC, etc.DL Basis for matchmakingMultiple profiles; multiple hierarchies

nameprovider

avgResponseTime?… FeeBased feeBasis+

paymentMethod+

15

Objectives that a client may havewhen consulting a Web Service

Provide the formallyspecified terminologyof the information usedby all other components

Semantic description of WebServices: - Capability (functional)- Interfaces (usage)

Connectors between components withmediation facilities for handling heterogeneities

WSMO Top-level Elements(http://www.wsmo.org)

Web ServiceImplementation

(not of interest in Web Service Description)

Choreography --- Service Interfaces ---

Capability

functional description

WS

WS

- Advertising of Web Service- Support for WS Discovery

client-service interaction interface for consuming WS - external visible behavior- communication structure - ‘grounding’

realization of functionality by aggregation- functional decomposition - WS

composition

Non-functional Properties

DC + QoS + Version + financial

- complete item description- quality aspects - Web Service

Management

WS

Orchestration

WSMO – the Web service element

Semantic Web Service Broker

Client

Services

VTA

VTA WS ‘Trip Booking’

Capability

provides

Chor.Interf.

Flight Request

Hotel Request

Book Flight

Book Hotel

if hotel = Ø flight.arrivaltime = hotel.arrivaltime

flight information

if flight = Ø

hotel information

process (control + data flow) of goals

Orchestration Definition

VTA

VTA WS ‘Trip Booking’

Capability

provides

Chor.Interf.

Flight Request

Hotel Request

Book Flight

Book Hotel

if hotel = Ø

if flight = Ø

process (control + data flow) between “states” + communication behavior of orchestrating Web Service

Flight WS

Capability

Interface (Chor.)1) get request2) provide offer 3) receive selection4) send confirmation

Orch. ..

Hotel WS

Capability

Interface (Chor.)1) get request2) provide offer 3) receive selection4) send confirmation

Orch. ..

flight request

avaiable flights

hotel request

avaiable hotels

book request booking confirmation

book request

booking confirmation

Runtime Orchestration

LINKED DATA EFFECT

25 Billion Statements

Linking Open Data cloud diagram, by Richard Cyganiak and Anja Jentzsch. http://lod-cloud.net

How?

Data.gov.uk Applications

RISE OF REST

RESTful Service

• Lightweight compared to SOAP/WSDL• Use HTTP methods explicitly (GET, POST, PUT,

DELETE)• Stateless• Expose directory structure-like URIs• Data transfer using XML, JavaScript Object Notation

(JSON), or both.

RESTful Service Takeup

1876 APIs

4736 Mashups

REST vs SOAP API Searches

http://www.google.com/insights/search/#q=soap%20api%2Crest%20api&cmpt=q

LINKED DATA AND SERVICES

Linked Open Services

http://www.linkedopenservices.org/

MicroWSMO & WSMO-Lite

37

WSDL

39

SAWSDL

But:no predefined semantics!

40

WSMO-Lite in WSDL

MicroWSMO• Built on top of hRESTS which introduces the

service model structure on Web pages–service (+ label)–operations (+ address, method)–input, output

• MicroWSMO extends hRESTS–model, lifting, lowering

• Applies WSMO-Lite semantics

41

MicroWSMO

MicroWSMO

Service

OperationInput

Parameter

MicroWSMO

Service

OperationInput

Parameter

MicroWSMO

46

Minimal Service Model

Service Template

47

RDFS/WSML-Core taxonomy e.g., ServiceFinder

ServiceTemplate

hasInput

hasOutput

hasFunctionalCategory

hasPreference

hasRequirement

RDF-based domain ontologye.g., RDFS/WSML-core, OWL/WSML-DL, WSML-Rule

RDFS/WSML-Core preference modele.g., WSMO Pref, U-Sevilla

WSMO-Lite annotatione.g., Condition, Effect WSML Flight/Rule

logical expression

RDF-based context ontologye.g., RDFS/WSML-core, OWL/WSML-DL, WSML-Rule

hasContextualSens.

Deployment

Process Editor

Discovery

Service Lifecycle

ServiceAnnotation

Process Modeling

Process Execution

Analysis & Monitoring Invocation

Resource-Orientation (ROSM)

49

ServicedResource

ServicedResourceCollection

Service

Operationsupports

Method

ResponseCode

HTTP *

* http://www.w3.org/2006/http#

basedOn

Request Response

Parameter

Optional Parameter

Required Parameter

1 2

1. requestURIParameter requestBodyParameter requestHeaderParameter

2. hasBody

collects

EXAMPLE APPLICATIONS

Example 1: House Hunting …

… public transport …

… schools

www.tauntonschool.co.uk

Behind the Scenes

Train stations

Bus stops

Schools

Real estate

Public Data and Services

publishingService Broker

Invocation Engine

discovery

invocation

CURRENT AND FUTURE WORK

The Future Internet – Enabler for Global Business Networks

Manu-facturing

UrbanManagement

eEnergyTransportLogistic

….

Network of the Future

Cloud Computing

Internet of Things

Internet of Services

Internet of the Future

Consumers

Suppliers

Wholesalers

RetailersCarriers

Manufacturer

Governments

© SAP 2010 /

The Internet of Services – Global Service Delivery Supply Chain

A Single Market for Services

SaaS, On-DemandEnterprise Suites

Cloud Services

ServiceMarketplaces

Multi-Enterprise Business process

platforms

B2B Gateways

Business ProcessOutsourcing

Business Process Platform

Service Delivery FrameworkService

AggregatorServiceHoster

ServiceProvider

ServiceGateway

ServiceBroker

ServiceChannel Maker

Service-Oriented Architecture

© SAP 2010 /

ServiceAggregator

ServiceHoster

ServiceProvider

ServiceGateway

ServiceBroker

ServiceChannel Maker

The Internet of Services – Unified Service Description Language (USDL)

Service Transformation stands for a value-driven, smooth and effective provision of services along the Global Service Delivery Supply Chain

Service Transformation implies that Services are being Described considering business, operational and legal requirements Maintained, extended and assembled where needed Applying a common notation named USDL

© SAP 2010 /

W3C USDL Incubator

http://www.linked-usdl.org/

This group is based on the idea of combining two Web-related concepts to help solve some of the long-standing challenges involved in building and combining software:

1. RDF, the Resource Description Framework…. RDF is the basis for Linked Data and the Semantic Web.

2. With RESTful APIs and RESTful Web Services, ….

The Linked Data Platform is envisioned as an enterprise-ready collection of standard techniques and services based on using RESTful APIs and the W3C Semantic Web stack

Summary• Web services successful history in corporate settings

–Supporting reuse of software components• Semantic Web services

–Lots of research–Takeup limited

• New trends–RESTful services–Linked Data portals/applications

• Manage applications which make use of these trends

• Fit to the goals, needs and contexts of users

Acknowledgements