A view-based approach for semantic service descriptions

Carsten Jacob, Heiko Pfeffer, Stephan Steglich, Li Yan, and Ma Qifeng

19.04.23

• Semantic service descriptions can be applied to enhance automatic service selection, composition, and invocation processes

• Service providers and consumers consider service descriptions from a different perspective– Publish and advertise a service

• Service category, grounding, …– Search for a particular kind of functionality

• Service effect, costs, find similar services, …Potential for abstracted views for both parties

– Move complexity inside the automatic service matching process

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Motivation

• Abstracted semantic view for service provider and consumer based on an internal representation

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Three views for service description representation

C

C1 C2

C11 C12

Concept basedService Provider View

Effect basedService Requester View

Internal Representation

Concept

Transformation

Effect

Tranf

orm

ation

E E

E’

E’’

E’+G

E’+H

E’+G+I

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Embedding

Service Request

Service Composition Discovery

Service Discovery & Matching

Service Binding & Execution

Service Publication

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Internal service view, service model (IOPE*)

Element Representation Description

Name String Unique name of the service.

Category Semantic concept reference (definition in ontology)

Category of the service. Services of one category are only different with regard to their context, QoS parameters, and grounding.

Input parameters

List of concept references

Semantically represented input parameters.

Output parameters

List of concept references

Semantically represented output parameters.

Precondition List of statements Preconditions for the execution of the service.

EffectRule List of rules Rules specifying the possible effects of the service.

Service context List of statements Context parameters of the service, e.g., location.

QoS Parameter List of statements Quality of Service parameters.

1 <Service name="LightSwitch1">2 <hasCategory resource="#LightSwitch"/>3 <hasInput resource="#OnOffValue"/>4 <hasOutput resource="#OnOffValue"/>5 <hasEffectRule ID="Rule1">6 [(#lightSwitch1 #hasInput #OnValue) --> (#lightSwitch1 #hasEffect #Bright1)]7 </hasEffectRule>8 <Bright ID="Bright1"/>9 <hasContextParameter>10 <ServiceContext ID="EffectContext1">11 <hasLocation resource="#Room15"/>12 </ServiceContext>13 </hasContextParameter> 14 </Service>

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LightSwitch example

<Input ID=”#OnOffValue”><oneOf parseType=”Collection”>

<Thing about=”#OnValue”><Thing about=”#OffValue”>

</oneOf></Input><Input ID=”#OnValue”>

<hasValue parseType=”String”>on</hasValue></Input><Input ID=”#OffValue”>

<hasValue parseType=”String”>off</hasValue></Input>

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Example: definition of concepts

• Categories are defined by their features– Input or output parameter– Precondition– Effect rule

• Service provider– Browses the category tree and

adds service (and category if necessary)

– Lists the features of the service to enable an automatic classification

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Service provider view

A

B C

1

12

13

1 3Service1

1 2 5Service5

1 4Service2

1 6 7Service4

Category tree and features: Services:

A

B C

1

12

13 D 1

4

E 12 5

F 16 7

New category tree and features:

Element Input and transformation

Category Selection of a proper category class from the tree OR string input (name and domain)

Input and output parameter

List of allowed values OR suitable range OR selection of a proper existing concept

Precondition List of possible values OR range OR facts (referring to concept classes)

Effect rule Rule with condition and effect• [ServiceID] hasInput [X]• [ServiceID] hasMatchedPrecondition [Y]• [ServiceID] hasContext [Z]

Service context Property and value OR complex description (also defining new concepts)

QoS parameter Property and value OR complex description (also defining new concepts)

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Service provider view – transformation rules

• Three phases1. User specifies goal by selecting a general effect2. User selects possible sub-effects, which are presented to specify

the effect in more detail3. User selects additional effects from proposals

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Service requester view

E E

E’

E’’

E’+G

E’+H

E’+G+IEffect based

Service Requester View

Requested Effect

Possible Sub-Effects

Possible Side Effects

Example:(E) call-setup(E‘) to nearby restaurant(E‘+H) send SMS to friends in buddylist

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Exemplary service classification

Video TextVoiceLocation Person

ContactFindBook

... ......

Bar VolleyballRestaurantBuddy Cinema

• Parse service effect rules to create effect tree if a new service is published

• Semantic relationships among effects enable the definition of sub effects

• According to the user‘s choice proper service categories are marked– Final selection is based on

• Available input parameters (manually provided or derived)

• QoS parameters, user ratings, …

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Service requester view - transformation

int step=0;node root = null; WHILE (step < maxEffectsPerRule) { r = getNextRule(); IF (r.numberOfEffects() = step) { IF (r.factsFulfilled() = true) { FOR (all Leaves){ IF (Leaf l.getEffects(). isSubsetOf(r.getEffects())){ createNode(Effects); } } } } ELSE { step++; }}

• Semantic Web Services description– Based on OWL-S– Object references defined in ontologies (OWL/RDF) to

enable inference (SWRL, Jena rules, …) and classification using reasoner programs

• Workflow descriptions for consideration of compositions– Web Services Business Process Execution Language (WS-

BPEL), Web Service Choreography Interface (WSCI), Business Process Modeling Language (BPML)

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Grounding

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Possible Embedding in IP Multimedia Subsystem (IMS)

LCAI Proxy

Services/Application Servers

BindingsIMS Domain

SIP Messages

Service Enablers

CSCF HSS

WebServices

SIPSIP Client

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Example user subscription

A

A1 A2

A1a A2a A2b

A2 A2aA2b

A

User subscription

Available services on the user‘s mobile phone

Service knowledgerepository

Thank you for your attention!

Carsten Jacob (carsten.jacob@fokus.fraunhofer.de)

19.04.23

16

BACKUP

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Excursion: Semantic Web technologies

Describing data

Describing knowledge

Making use of knowledge

Trust and Proof

XML XMLSchemaNamespaces

RDF RDFSchemaOWL

ReasonersRule languages

Proof languages...

Query languages

Describing data

Describing knowledge

Making use of knowledge

Trust and Proof

XML XMLSchemaNamespaces

RDF RDFSchemaOWL

ReasonersRule languages

Proof languages...

Query languages

following Tim Berners-Lee XML2000, http://www.w3.org/2000/Talks/1206-xml2k-tbl/

• Explicit formal specification of objects or concepts and their relationships– Gruber (1993): “an explicit specification of a

conceptualization”• Describes:

– Classes– Individuals– Attributes/ Properties– Relationships

• More expressiveness: class relationships (disjointness, ...), cardinalities, property characteristics (symmetry, ...), restrictions, ...

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Excursion: Ontology

Gruber, T. R.. (1993). Toward principles of the design of ontologies used for knowledge sharing. Presented at the Padua workshop on Formal Ontology, March 1993, later published in International Journal of Human-Computer Studies, Vol. 43, Issues 4-5, November 1995, pp. 907-928.

• Layering:– OWL Lite: basic functionality– OWL DL: all conclusions are computable, ensures decidability– OWL Full: no restrictions concerning the OWL vocabulary

• Characteristics:– XML, human readable text– Distributable, support for classification and inconsistency

checks, extensible, ...– Standardized, widely-used, tool support – Web-oriented: e.g., resource identification, Open World

Assumption (OWA), but no Unique Name Assumption (UNA)

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Excursion: Web Ontology Language (OWL)

http://www.w3.org/TR/owl-ref/

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Excursion: OWL Example<?xml version="1.0"?><rdf:RDF ... xml:base="http://www.co-ode.org/ontologies/pizza/2005/10/18/pizza.owl"> <owl:Ontology rdf:about=""> ... <owl:imports rdf:resource="http://protege.stanford.edu/plugins/owl/protege"/> </owl:Ontology> ... <owl:Class rdf:ID="Pizza"/> <owl:Restriction> <owl:onProperty> <owl:ObjectProperty rdf:ID="hasTopping"/> </owl:onProperty> <owl:allValuesFrom> <owl:Class> <owl:unionOf rdf:parseType="Collection"><owl:Class rdf:ID="FruitTopping"/> ... <owl:Class rdf:ID="CheeseTopping"/></owl:unionOf> </owl:Class> </owl:allValuesFrom> </owl:Restriction> </owl:intersectionOf> </owl:Class> ...

http://www.co-ode.org/ontologies/pizza/2005/10/18/pizza.owl

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Possible Embedding in IMS

Semantic Service Matching

Sh/Si

S-CSCF

AS

HSS

Application Server

Application Logic

AS-ILCM AS-OLCM

ISCCx

iFC

SIP INVITE/SUBSCRIPTION

1

2

AS Selection ~> iFC

Rule1

Rule2

...

RuleN

LCAI_SE

LCAI SE

3S

E S

election

4

Rule Update

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Service composition example

<S_ID=1>

<S_ID=2>

<S_ID=3>

<S_ID=4>

<S_ID=5>

1

1 2

1 2

1 2

1 2

1 2

1 2

1

1 2

1 2

1

1Global Output

Global Input