Silicon Valley Semantic Web Meet Up

Semantic Web services in a Nutshell
Federico M. Facca and RetoKrummenacher

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Federico M. Facca
federico.facca@sti2.at
RetoKrummenacher
reto.krummenacher@sti2.at
http://www.sti-innsbruck.at

Semantic Technology Institute Innsbruck
Institute at the University of Innsbruck (est. 1669) which is currently the largest education facility in Austria.
Founded as a research group under the guidance of Prof. Dieter Fensel in 2003.
Status of a research institute at the University of Innsbruck since January of 2006.
Main research areas: Semantic Web, Semantic Web Services, Service-Oriented Architectures.
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Projects
Currently involved in a number of FP6 and FP7 EU projects related to the Semantic Web and Semantic Web Services such as
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STI International

Making this real…STI International
The mission of Semantic Technology Institute Internationalis to establish semantics as a core pillar of modern computer science.
STI is organized as an association of jointly interested academic, industrial and governmental parties.
It provides services to facilitate research, education, and commercialization activities around semantic technologies and the service web beyond the boundaries of individual projects or initiatives.

STI International – The Members

The Future Internet

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Overview
Background and Motivation
Service Web
Semantic Web Services
SOA4All: A Global Service Delivery Platform
Highly Flexible Service Offer for the Future Internet
Conclusion

BACKGROUND
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The Rise of the Service Economy
[IBM Survey on national labor data, 2004]
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Background
Computer science is entering a new generation
The previous generation was based on abstracting from hardware
The emerging generation comes from abstracting from software and sees all resources as services in aservice-oriented architecture(SOA)
In a world of services, it is the service that counts for a customer and not the software or hardware components that implement the service
Service-oriented architectures are rapidly becoming the dominant computing paradigm
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From SaaS to XaaS
In a service-oriented world everything is a service
Programs are services
Devices are services
Different types of media (audio, video, text) are integrated
Environments are dynamic and open
Mobility; Ubiquity; RFID
Service orientation needs to scale up to open and dynamic environments of billionsof services
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XaaS: Amazon – S3 & EC2
“Infrastructure as a service”
Amazon Simple Storage Service (S3)
Write and read objects up to 5GB
15 cents GB / month to store
20 cents GB / month to transfer
Amazon Elastic Compute Cloud (EC2)
allows customers to rent computers
on which to run their own computer
applications
virtual server technology
10 cents / hour
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State of affairs
Current SOA solutions are however still restricted in their application context to companies’ intranets
A ‘Service Web’ with billions of services depends on resolving fundamental challenges that SOA does not address currently
Currently there exists only around 30000 Web services on the Web
Number of Web services found during the past 26 months
[seekda.com, August 2009]
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SERVICE WEB
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Requirements for Service Web
A Service Web with billions of services can be realized only if SOA can deal with
Openness– everybody can act as a provider or consumer of services
Heterogeneity– services are created in isolation from one another thus interoperability is an issue
Distributedness– there is no central control of services. Services can appear, change or disappear at any time in an uncontrolled fashion
Scalability– with so many services available on the Service Web the Human may become the bottleneck
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How to enable Service Web?
A Web-scale service delivery platform
Any time and anywhere service consumption
Heterogonous execution platforms
New paradigms to engineer, integrate, deploy services
Flexibility
Customization
Semantics as scalability enabler
Service customization
Service federations
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[Prof. dr. Lutz Heuser, SAP: “Towards afuture Internet of Services”]

Semantics and Service Web
Semantics is a required key enabler for automation of the service life-cycle at Web-scale, but if misused it may become a bottle-neck
It does not make sense to describe (or assume that) Amazon services in a complete way (i.e. using ~30 billions RDF triples!)
In a world of billions of services it may cost too much to find the “optimal” service in relation to the reward of having actually found the optimal solution
Pragmatic approaches in service discovery will focus on utility, i.e., stop the search process when a service is found that is “good” enough to fulfill a request
Also, it is unrealistic to assume that semantic descriptions of services are correct and complete, i.e., duplicate the functionality of a service at the description level
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SEMANTIC WEB SERVICES
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Semantic Web and Web Services
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It’s all about automation!
Web Services
UDDI, WSDL, SOAP
Semantic Web
Services
Dynamic
WWW
URI, HTML, HTTP
Semantic Web
RDF, RDF(S), OWL, etc.
Static

Top-level elements defined by WSMO
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Objectives that a client may
have when consulting a Web Service
Semantic description of Web
Services:

Capability (functional)
Non-functional properties
Interfaces (usage)

Provide the formally
specified terminology
of the information used
by all other components
Connectors between components with
mediation facilities for handling
heterogeneities

Ontologies
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Ontologies
In WSMO, Ontologies are the key to linking conceptual real-world semantics defined and agreed upon by communities of users
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Class ontology sub-Class wsmoElement
importsOntology type ontology
usesMediator type ooMediator
hasConcept type concept
hasRelation type relation
hasFunction type function
hasInstance type instance
hasRelationInstance type relationInstance
hasAxiom type axiom
Examples:

The Location Ontology (http://www.wsmo.org/ontologies/location) contains the concepts “Country” and “Address”
The Location Ontology (http://www.wsmo.org/ontologies/location) contains the “Austria” and “Germany” instances

Ontology Specification
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Non functional properties author, date, ID, etc.
Imported Ontologies importing existing ontologies where no heterogeneities arise
Used mediators OO Mediators (ontology import with terminology mismatch handling)

Ontology Elements:
Concepts set of entities that exists in the world / domain
Attributes set of attributes that belong to a concept
Relations define interrelations between several concepts
Functions special type of relation (unary range = return value)
Instances set of instances that belong to the represented ontology
Axioms axiomatic expressions in ontology (logical statement)
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The Web Service Element
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The Web Service Element
WSMO Web service descriptions consist of non-functional, functional, and the behavioral aspects of a Web service
A Web service is a computational entity which is able (by invocation) to achieve a users goal. A service in contrast is the actual value provided by this invocation
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Web Service Non-Functional Properties
Non-functional properties:
Accuracy - the error rate generated by the service
Financial - the cost-related and charging-related properties of a service
Network-related QoS - QoS mechanisms operating in the transport network which are independent of the service
Performance - how fast a service request can be completed
Reliability - the ability of a service to perform its functions (to maintain its service quality)
Robustness - the ability of the service to function correctly in the presence of incomplete or invalid inputs.
Scalability - the ability of the service to process more requests in a certain time interval
Security - the ability of a service to provide authentication, authorization, confidentiality, traceability/auditability, data encryption, and non-repudiation
Transactional - transactional properties of the service
Trust - the trust worthiness of the service
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Example:

If the client is older than 60 or younger than 10 years old the invocation price is lower than 10 euro

Web Service Capability
A capability defines the Web service by means of its functionality
Precondition - the information space of the Web service before its execution
Assumption - the state of the world before the execution of the Web service
Postcondition - the information space of the Web service after the execution of the Web service
Effect - the state of the world after the execution of the Web service
Shared Variables - variables that are shared between preconditions, postconditons, assumptions and effects
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Class capability sub-Class wsmoElement
usesMediator type {ooMediator, wgMediator}
hasNonFunctionalProperties type nonFunctionalProperty
hasSharedVariables type sharedVariables
hasPrecondition type axiom
hasAssumption type axiom
hasPostcondition type axiom
hasEffect type axiom
Example:

The input for a birth registration service in Germany has to be boy or a girl with birthdate in the past and be born in Germany. The effect of the execution of the service is that after the registration the child is a German citizen.

Web Service Interface
An interface describes how the functionality of the Web service can be achieved (i.e. how the capability of a Web service can be fulfilled) by providing a twofold view on the operational competence of the Web service:
Choreography decomposes a capability in terms of interaction with the Web service
Orchestration decomposes a capability in terms of functionality required from other Web services
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Class interface sub-Class wsmoElement
usesMediator type ooMediator
hasChoreography type choreography
hasOrchestration type orchestration

Goals
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Goals
Goals are representations of an objective for which fulfillment is sought through the execution of a Web service. Goals can be descriptions of Web services that would potentially satisfy the user desires
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Class goal sub-Class wsmoElement
usesMediator type {ooMediator, ggMediator}
requestsCapability type capability multiplicity = single-valued
requestsInterface type interface
Example:

A person named Paul has to goal to register his son with the German birth registration board

Example: Web Service Discovery
Distinguish between abstract service and a specific one
Abstract service: a computational entity able to provide many services
Service: a concrete invocation of a Web service
The task
Client is interested in getting a specific service
Identify possible service providers, which may be able to provide the requested service S for its clients
Discovery
Given a goal and some Service repository determine the set of relevant service providers
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Example: Web Service Discovery
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Web service:
sells train tickets
for trips within
Europe
Goal: buy a
travel ticket from
Vienna to
Berlin
Reasoning
Travel Ticket
Europe
Train
Ticket
Match!
Vienna
&
Berlin

Mediators
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Mediators
Mediation
Data Level - mediate heterogeneous Data Sources
Protocol Level - mediate heterogeneous Communication Patterns
Process Level - mediate heterogeneous Business Processes
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Mediators
Four different types of mediators in WSMO
ggMediators: mediators that link two goals. This link represents the refinement of the source goal into the target goal or state equivalence if both goals are substitutable
ooMediators: mediators that import ontologies and resolve possible representation mismatches between ontologies
wgMediators: mediators that link Web services to goals, meaning that the Web service (totally or partially) fulfills the goal to which it is linked. wgMediators may explicitly state the difference between the two entities and map different vocabularies (through the use of ooMediators)
wwMediators: mediators linking two Web services
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The WSMO Framework
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Conceptual Model for SWS
Execution Environment for SWS
Formal Language for WSMO
Ontology & Rule Language for the Semantic Web

SOA4All: A GLOBAL SERVICE DELIVERY PLATFORM
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Motivation
The Web currently contains 30 billion Web pages
Children can create Web pages
BUT the Web contains only ~28,000 ‘true’ Web services (seekda.com)
Only technologically experienced people can create and work with Web services

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Two Core Objectives
“Billion of Services”: SOA4All will transform the Web into a domain where billions of parties are exposing and consuming services in a seamless and transparent fashion.
“4 All”: SOA4All will integrate the service world of large enterprises, SMEs, and end-users enabling them to engage as peers within a network of equals.
http://www. .eu

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Approach
Context: user profiles, execution monitoring, service data, social context
Web: openness, decentralization,
n:m relations, statelessness
Semantics: formal models, service and goal descriptions, processes
Web2.0: content prosumers,
service prosumers, communities

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SOA4All Architecture
‘semantic service descriptions’
‘semantic process descriptions’
‘semantic goal descriptions’

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Semantic Spaces
Use of semantics in SOA4All requires a scalable and distributed data management infrastructure for:
Repository for service annotations in RDF
Infrastructure for sharing monitoring and execution data
Process repository of composition information
User profile management infrastructure
Semantic Spaces provide:
Web-style publish and read operations (persistent storage)
Shared data management
Interaction mechanism for collaborative activities
Event-based notification services

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Annotation of Services
Representation Languages
WSML
Reasoners
Annotation Mechanisms
WSMO-Lite, MicroWSMO

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?
Annotation of Services
ontology FinancialServices
concept CreditCheckService
subConceptOf FinancialService
....
"?s[modelReference hasValue ?cat]
memberOf wsl#Service and
?cat subConceptOf FinancialService"
<service
name="HanivalCreditCheck"
sawsdl:modelReference=
"http://ex.com/FinancialServices#
CreditCheckService"
...
Reasoner
?s=HanivalCreditCheck
?s=PayPalCreditService
?s=...

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Lightweight Service Modelling
A common service model is expressed in RDF Schema, using only the WSMO features motivated by SAWSDL references
WS-* Stack services attached to lightweight semantic descriptions via SAWSDL
RESTful services attached to lightweight semantic descriptions via microformants

WSDL Simplified
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Web service
input
Operation 1
output
input
Operation 2
.
output
.
.
input
Operation N
output

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Semantics in Service Model
F
N
B
I
SAWSDL
modelReference
Web service
input
Operation 1
output
input
Operation 2
.
output
.
.
input
Operation N
output
Functional,
Non-Functional,
Behavioural,
Information model

MicroWSMO
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The service is described for humans on a Web page
hRESTS allows aspects of the service description to be annotated
microWSMO uses these annotations to refer to elements of the same lightweight service modelling ontology as WSMO-Lite

WSMO-Lite Annotation Tool
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Goal Formalisation
Semantic goal descriptions match the WSMO-Lite service annotations.
SPARQL can be used as simplest discovery algorithm by matching operations, input, and output messages.
More sophisticated matching (based on conditions, effects or NFPs) requires axiomatic reasoning (e.g. WSML).
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Example: Service Discovery
SOA4All Studio: Consumption Platform
ervice
G
SOA4All Runtime:
DSB & Platform Services
S
Ranking & Selection
Discovery
Q
O
ntology
Crawler
Reasoner
O
S
Communication via DSB
S
Service Registry
uery
O
Q
S
Semantic Space
oal
G

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Example: Service Discovery
SOA4All Studio: Consumption Platform
S
ervice
G
SOA4All Runtime:
DSB & Platform Services
S
Ranking & Selection
Discovery
O
Q
ntology
Crawler
Reasoner
O
S
S
Service Registry
uery
O
Q
S
Semantic Space
oal
G

Service Composition
SOA4All Studio: Provisioning Platform
oal
G
P
SOA4All Runtime: DSB & Platform Services
Design-Time Composer
Template Generator
ntology
Reasoner
Composition Optimizer
Neglected is the monitoring data that is provided by the DSB to the Composition and Execution.
O
O
Q
Execution Engine
O
uery
„DISCOVERY“
Q
G
Semantic Space
rocess
P
P

Service Composition
SOA4All Studio: Provisioning Platform
oal
G
P
SOA4All Runtime: DSB & Platform Services
Design-Time Composer
Template Generator
ntology
Reasoner
Composition Optimizer
Neglected is the monitoring data that is provided by the DSB to the Composition and Execution.
O
O
Execution Engine
O
uery
„DISCOVERY“
Q
G
Semantic Space
rocess
P
P

HIGHLY FLEXIBLE SERVICE OFFER FOR THE FUTURE INTERNET
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From one that fits allto personalized software
Traditional software engineering and provisioning solutions suffer from lack of flexibility
A software to fits all type of customers
Modern trends in products variability showed how customization increase revenues
Web scale delivery of customized software
How can we achieve mass customized software as with traditional products?
Economy showed that the only way to enable small competitors to stay on the market is by federating and providing high-added-value service bundles
Dynamically created federations of services to better match user’s demand
How can we enable providers to federate together at web-scale with a high degree of automation?
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Parametric Services and Semantics
High level service customization can be achieved by making services parametric
Automatic deploy-time and run-time customization of parametric services requires proper languages and methods
Semantics enable description of such aspects and automatic reasoning over them through application of problem solving methods and parametric design
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Service Federations and Semantics
Global scale delivery of services, including services provided by small providers can be achieved by automated federation of services
Requires tools and languages for enabling negotiation among services and service providers
Semantics is the means to enable negotiation among providers, supporting heterogeneity resolution and making possible optimization of the federation via reasoning techniques and problem solving methods
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CONCLUSIONS
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Conclusion
Future Internet requires:
Platforms and languages for Service Web
Methods and languages for mass customization of services
Semantic Web techniques can be used to provide approximate descriptions of services …
… however not as a replacement of service technology.
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Summary
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Global service delivery
Web services stagnate
Semantic Web services
SOA4All