1. Quan Z. Sheng and Boualem Benatallah
ContextUML: A Modeling Language for Model-Driven Development of Context-Aware Web Services
Quan Z. Sheng and Boualem Benatallah
School of Computer Science and Engineering
The University of New South Wales (UNSW)

2. Agenda
Development of Context-Aware Web Service (CAS) : Problem Statements
Contexts and Context-Aware Web Services
CAS Development Challenges
ContextUML
Context Modeling
Context Awareness Modeling
Related Work and Future Directions 2
Q. Z. Sheng and B. Benatallah
11 July 2005, ICMB 2005

3. What Are Contexts Many different definitions for contexts
“Any information that can be used to characterize the situation of an entity. An entity is a person, place, or object that is considered relevant to the interaction between a user and an application, including the user and application themselves” [Dey and Abowd at Georgia Tech.]
Contexts are application specific
Travel
planing
Currency
exchange
Weather 3
Q. Z. Sheng and B. Benatallah
11 July 2005, ICMB 2005

4. Context-Aware Web Services (CASs)
Provide relevant information/services to users using context information
More friendly, personalized, and intelligent services
restaurant finding service (context-aware vs. non context-aware)
A promising technology for mobile businesses
Museum/campus guide, driving assistant, lunch assistant….
many more guides and assistants! 4
Q. Z. Sheng and B. Benatallah
11 July 2005, ICMB 2005

5. Context-Aware Web Service (cont.) An Example CAS
Recommend attractions according to user’s location, weather, language:
1) If weather is bad (harsh weather): indoor attractions
2) If description is not in preferred lang.: translate to the preferred lang.
Subscribe personal preferences (e.g., preferred attractions, language)
Harsh weather is defined as:
temperature>40°C and rainlikelihood>80%
Attractions Searching
Service (ASS) 5
11 July 2005, ICMB 2005

6. To Date, CASs Are Still Hard to Build…
Current Web service standards are not sufficient for describing and handling context information
UDDI, WSDL, SOAP, …
Many Web service development tools exist (e.g., Java2WSDL), but development of CASs cannot benefit directly from them
Lack of generic approach for formalizing the CAS development
Contexts management is implemented in an ad-hoc manner
Heterogeneous and dynamic contexts
Contexts quality 6
Q. Z. Sheng and B. Benatallah
11 July 2005, ICMB 2005

7. Attractions searching
Many Questions…
Attractions searching
service
What kinds of contexts? Where to get?
What if contexts are unavailable or imperfect?
How to make sure the context is the best one?
What if contexts with no providers?
CAS
developer
How to use contexts in CASs?
How to use legacy Web services implementation in CASs? ……
Developing CASs is cumbersome and time-consuming, especially when they are complex. 8
11 July 2005, ICMB 2005

8. Agenda
Development of Context-Aware Web service (CAS) : Problem Statements
Contexts and Context-Aware Web Services
CAS Development Challenges
ContextUML
Context Modeling
Context Awareness Modeling
Related Work and Future Directions
11 July 2005, ICMB 2005

9. ContextUML: Metamodel (abstract syntax)
Context Modeling
Context-Awareness Modeling
Service
AtomicContext
CompositeContext 1
MechanismAssignment *
SourceAssignment
1..* *
Operation
CAObject
CAMechanism
Context
ContextSource * *
1..* *
1..*
1..*
input
output
0..1
0..1
Message
ContextBinding
ContextTriggering
ContextService
ContextService
Community * *
part *
0..*
1..*
1..* *
member
Part
ContextConstraint
Action
11 July 2005, ICMB 2005 8

10. ContextUML: Context Modeling
Context Type
Atomic contexts: low-level contexts, directly provided by context sources. (e.g., temperature, rainLikelihood)
Composite contexts: high-level contexts, no direct providers, aggregate multiple atomic or composite contexts (e.g., harshWeather)
AtomicContext
CompositeContext *
SourceAssignment * …
Context
ContextSource *
1..*
ContextService
ContextService
Community * *
member
11 July 2005, ICMB 2005 9
Q. Z. Sheng and B. Benatallah

11. ContextUML: Context Modeling (cont.)
Context source models the resources from which contexts are retrieved
Two types context sources: context service and context service community
Context service: collect, refine, and disseminate context
Global Weather Service,
Sydney (12/07/05) Temperature: 11°C-17 °C
Rainlikelihood: 40% 10
11 July 2005, ICMB 2005

12. ContextUML: Context Modeling (cont.) Context Service Community
Dynamic provisioning of optimal context information
Aggregate multiple context services, offering a unified interface, e.g., weather service community
When invoked, select the most appropriate context service based on a selection policy 1
request 2
selection 5
contexts
Weather services
community 4 3
globalWeather
forecastedWeather
weatherInfo.
weather4U 11
11 July 2005, ICMB 2005

13. ContextUML: Context Modeling (cont.) Context Service Community
The selection can be based on a set of Quality of Context (QoC) parameters
Precision: accuracy of context information (e.g., 10°C ±0.2 )
RefreshRate: update rate (e.g., every 30 seconds)
TrustWorthiness: how likely a context is correct. (e.g., good)
…..
QoC parameters are crucial to CASs. Imperfection of context information may make CASs misguide users
Attractions searching service might suggest a user to surf at Bondi Beach, although it is rainy and stormy!!! 12
Q. Z. Sheng and B. Benatallah
11 July 2005, ICMB 2005

14. ContextUML: Context Modeling (cont.) Context Service Community
Utility function:
Scorei(cs) is a criteria scoring function. Given a criteria i of context service
cs, returns a score.
SC is the set of the selection criteria (QoC: refresh rate, precision et.al.).
wi is the weight assigned to the criterium i
Context services
Scores
Best context service
csm 13

15. ContextUML: Context-Awareness Modeling
Comply with WSDL
(Web Services Description Language)
Service 1
MechanismAssignment
1..*
Operation
CAObject
CAMechanism
Context … *
1..*
1..* *
input
output
0..1
Message
ContextBinding
ContextTriggering * *
part
0..*
1..*
1..*
Part
ContextConstraint
Action 14
Q. Z. Sheng and B. Benatallah
11 July 2005, ICMB 2005

16. ContextUML: Context Binding
Context binding models the automatic binding of contexts to context-aware objects
Mapping between a context and a context-aware object
The value of the object is supplied by the value of the context
Attractions
Searching Service
city: string ….
Preferred attractions:
historical sites
Language: Chinese
Location: Sydney
Contexts
Input Parameters 15
Q. Z. Sheng and B. Benatallah
11 July 2005, ICMB 2005

17. ContextUML: Context Triggering
Context triggering models the contextual adaptation where services can be automatically executed or modified based on context information
Context constraint specifies that a certain context must meet certain condition in order to perform a particular operation
Context constraints are modeled as predicates. E.g., harshWeather = true; rainLikelihood >= 85%
Actions must be executed if and only if all the context constraints are evaluated to true
ContextTriggering * *
1..*
1..*
ContextConstraint
Action 16
Q. Z. Sheng and B. Benatallah
11 July 2005, ICMB 2005

18. ContextUML: Context Triggering (con.)
If weather is bad (harsh weather): indoor attractions
WeatherTrigger
Context triggering
harshWeather=true
FilterOutdoorActivities
Context constraint
Action 17
Q. Z. Sheng and B. Benatallah
11 July 2005, ICMB 2005

19. The Notation of ContextUML can be found in the paper
<<conuml.atomicContext>>
Location
LocationBinding
<<conuml.service>>
AttractionSearch
<<conuml.part>>
city
city: string
<<conuml.contextService>>
WhereAmI
<<conuml.contextBinding>>
<<conuml.atomicContext>>
Language
<<conuml.contextTriggering>>
LanguageTrigger
<<conuml.operation>> SearchAttractions
preferredLanguage: string
<<conuml.contextService>>
UserProfile
<<conuml.action>>
TransformLanguage
<<conuml.atomicContext>>
Temperature
{self.preferredLanguage <>
Attraction.descriptionLanguage}
The Notation of ContextUML can be found in the paper
<<conuml.message>>
ASSInput
<<conuml.message>>
ASSOutput
temperature: real
<<conuml.contextServiceCommunity>>
WeatherServices
city: string
attractions: Attraction[]
<<conuml.atomicContext>>
Rainlikelihood
<<conuml.mechnismAssignment>>
<<use>>
<<conuml.mechnismAssignment>>
rainlikelihood: real
<<conuml.contextServiceCommunity>>
WeatherServices
{self.harshWeather=true}
<<xsd.complexType>>
Attraction
<<conuml.contextTriggering>>
WeatherTrigger
attractionName: string
description: string
descriptionLanguage: string
location: string
mapimage: string
price: real
<<conuml.compositeContext>>
HarshWeather
<<conuml.action>>
FilterOutdoorActivities
harshWeather: boolean
getHarshWeather(temperature: real, rainlikelihood:real):boolean
ASS in ContextUML

20. ContextUML: Design Flexibilities
Separation of context awareness from service components
Ease the development and maintenance of CASs
Possible to use legacy codes of Web services in developing CASs.
Context service communities:
More flexible context provisioning
More robust context provisioning
Composite context:
More power, any high-level contexts useful in CASs 19
Q. Z. Sheng and B. Benatallah
11 July 2005, ICMB 2005

21. Agenda
Development of Context-Aware Web service (CAS) : Problem Statements
Contexts and Context-Aware Web Services
CAS Development Challenges
ContextUML
Context Modeling
Context Awareness Modeling
Related Work and Future Directions
11 July 2005, ICMB 2005

22. Related Work
Context-aware Web service: Keidl and Kemper (TU München, WWW’04)
Model-driven Web services development: Skogan , Gronmo, and Solheim (SINTEF, EDOC’04), Baina, Benatallah, Casati, and Toumani, (Uni. of NSW, CAiSE’04), Ceri et.al., (Uni. of Milano, WISEW’03)
Very few research proposals have been presented on model-driven development of context-aware Web services 20
Q. Z. Sheng and B. Benatallah
11 July 2005, ICMB 2005

23. Future Work Thanks, comments?
Generate completed, executable implementation of CASs from ContextUML models
BPEL (Business Process Execution language) specifications
Extend ContextUML to support context-aware composite Web services
Integrate semantic issues to context services for QoC-based context services selection
Thanks, comments? 21
Q. Z. Sheng and B. Benatallah
11 July 2005, ICMB 2005