Composing Web Services on the Semantic Web by Brahim Medjahed

1
Composing Web Serviceson the Semantic Webby
Brahim Medjahed

• Presented by
• Dohan Kim
• Lichun Zhu

2
Outline

• Semantic Description of Web Services
• Composability Model for Web Services
• Automatic Composition of Web Services
• Summarization and Conclusion

3
Semantic Description of Web Services

• Web Services Description Language (WSDL)
• Extending WSDL with Semantic Capabilities
• Providers, Composers, and Consumers
• Automatic Composition of Web Services
• The approach for combining the concepts of Web
  Services and Ontology

4
Ontology-based description of Web Services ( WSDL
Concept)
Binding
Name
Input
1N
10,1
1N
11
Parameter
Service
Operation
Output
1N
1N
10,1
Data Type
11
11
11
Name
Name
5
Semantic Description of Web Services

• Mode
• Notification, One-way,
• Solicit-response, Request-response
• Message
• A Message M is defined as a tuple ( P, T, U, R )
• P is a set of parameter names
• T P ? DataTypes
• U P ? Units
• R P ? Roles

6
Ontology-based description of Web Services (
Revisited)
Mode
Business Role
Binding
11
Name
Input
11
1N
1N
11
10,1
Parameter
Service
Operation
Output
1N
1N
10,1
Data Type
11
11
11
11
Name
Name
Unit
7
Semantic Description of Web Services

• Purpose
• Function, Synonyms, Specialization
• Function Business functionality defined within
  a given taxonomy
• Synonyms A set of alternative function names
• Specialization A set of characteristics of an
  operations function

8
Semantic Description of Web Services

• Category
• Domain, Synonyms, Specialization
• Domain Area of interest defined within a given
  taxonomy
• Synonyms A set of alternative domains
• Specialization A set of characteristics of an
  operations domain

9
Semantic Description of Web Services

• Quality
• Fees, Security, Privacy
• Fees Dollar amount needed to execute an
  operation
• Security A boolean that specifies whether an
  operations messages are securely exchanged
• Privacy A set of input and output parameters
  that are not divulged to external entities

10
Ontology-based description of Web Services
Domain
Synonym
Specialization
Mode
1N
Business Role
11
Binding
11
Category
Name
Input
11
1N
11
1N
11
10,1
Parameter
Service
Operation
Output
1N
1N
10,1
Data Type
11
11
11
Name
11
Description
Name
11
Unit
Description
11
Purpose
1N
Quality
11
11
1N
11
Synonym
Specialization
11
Function
Fees
Security
Privacy
11
Semantic Description of Web Services

• Defining Web Services and Operation
• Web Service
• A Web service WSi is defined by a tuple
• ( Descriptioni, OPi, Bindingsi, Purposei,
  Categoryi )
• Operation
• An operation OPik is defined by a tuple
• ( Descriptionik, Modeik, Inik, Outik, Purposeik,
  Categoryik, Qualityik)

12
Composability model for Web Services

• Mode and Binding Composability
• Message Composability
• Operation Semantics Composability
• Qualitative Composability
• Composition Soundness

13
Composability model for Web Services

• Mode Composability
• Two operations are mode composable if mode of
  each operation is paired as follows
• ( notification, one-way), ( one-way,
  notification)
• ( solicit-response, request-response)
• ( request-response, solicit-response)
• Binding Composability
• WSi ( Di, Oi, Bi, Pi, Ci ), WSj ( Dj, Oj, Bj,
  Pj, Cj )
• Two services are binding composable if Bi n Bj ?Ø

14
Composability model for Web Services

• Message Composability
• A message consists of one or more parameters,
  each having a certain data type
• Data Type Compatible (Direct vs Indirect
  Compatible)
• Input message of a service operation may use only
  a subset of the parameters of an output message
• Checking data type compatibility between input
  and output operation
• Checking Unit and Business Role between input and
  output operation

15
Composability model for Web Services

• OPik in WSi (Dik, Mik, Inik, Outik, Pik, Cik,
  Qik)
• OPjl in WSj (Djl, Mjl, Injl, Outjl, Pjl, Cjl,
  Qjl)
• Operation Semantics Composability
• Pik is compatible with Pjl
• Cik is compatible with Cjl
• Qualitative Composability
• Qik.Fees Qjl.Fees
• (Qik .Security true) ? (Qjl.Security true)
• Qik.Privacy ? Qjl.Privacy

16
Composability model for Web Services

• Composition Soundness
• Test whether composite services provides an added
  value
• Combining airline and hotel services
• Combining airline and lemon check services ?
• Composition Templates
• Stored Templates
• A Composition of services are sound if its
  template is a subgraph of a stored template

17
Automatic Composition of Web Services

• Four conceptually separated phases for automatic
  composition of Web Services
• Specification Phase
• Matchmaking Phase
• Selection Phase
• Generation Phase

18
Automatic Composition of Web Services

• Specification Phase
• Composite Service Specification Language ( CSSL )
• High level description of composite services
• Specification of the control flow between
  composite service operations
• Example CSSL - Car Broker Composite Service
• ltservice namecar broker/gt
• ltcategory domainbrokeragegt
• ltbinding nameSOAP/gt
• ........ (continued)

19
Automatic Composition of Web Services

• CSSL - Car broker composite service (continued)
• .
• ltmessage nameoffergt
• ltparameter nameprice typefloat unitUS
  dollar roleextendedPrice/gt
• ltparameter namemake typestring ....../gt
• ltparameter namemodel typestring ....../gt
• ltpararmeter nameyear typegYear ....../gt
• ltparameter namemileage typeinteger ....../gt
• lt/messagegt
• .......

20
Automatic Composition of Web Services

• CSSL - Car broker composite service (continued)
• .
• ltoperation namereceiveSpecialOffers modeone
  way/gt
• ltinput nameoffer/gt
• ltcategory domainautomobile dealergt
• ltsynonymsgt ltsynonym valuecar dealer/gtlt/synonyms
  gt
• ltpurpose functionprice-sales catalogue/gt
• ltqualitygt
• ltfees value0/gt
• .......
• lt/operationgt
• ltflow sourcegetPayingHistory
  targetapplyForFinancinggt

21
Automatic Composition of Web Services

• Matchmaking phase
• Generating composition plans using a matchmaking
  algorithm
• Mapping each operation of the composite service
  to one or more operations of existing service and
  check composability.
• Example functions of the algorithm
• purpose_compatible(), category_compatible(),
  quality_composable(), message_composable(),
  sound()

22
Automatic Composition of Web Services

• Selection phase
• Quality of Composition ( QoC ) parameters
• Ranking, Relevance, Completeness
• Composition Ranking( CT, STi )
• Composition Relevance
• Composition Completeness
• Plans with the highest ranking are returned first

23
Automatic Composition of Web Services

• Generation phase
• Generating a detailed description of a composite
  service
• List of outsourced services
• Mapping between composite and component service
  operations
• Mapping between messages and parameters
• Flow of control and data between component
  services
• Target language for CSSL specification
• Web Service Flow Language( WSFL), XLANG, etc

24
Target Language Example ( WSFL )
25
Conclusion

• Automatically generate composite services from
  high-level specifications of the desired
  composition
• Semantic description of Web Services
• Mode, Message, Operation,Purpose, Category, etc.
• Composability model for Web Services
• Automatic Composition of Web Services
• Specification, Matchmaking, Selection and
  Generation Phase

26
Questions and Answers

• Thank You !