contextual service interoperability · what is context (2/2) ? definition of context “a context...
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Interoperability Levels
What is Context DefinitionsExamples
Why own level?Contextual Interoperability
Model ViewInterface identification
Context Ontology LanguageOpen Issues + Discussion
Platform Interoperability(RPC)
Programming Language Interoperability(IDL)
Service Interoperability
SignatureLevel
ProtocolLevel
SemanticLevel
Service Interoperability
SignatureLevel
ProtocolLevel
SemanticLevel
ContextLevel
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What is Context (1/2) ?
Definition of Context Information“A context information is any information which can be used to characterize the state of an entity concerning a specific aspect”“An entity is a person a place or in general an object”“An aspect is a classification, symbol or value-range, whose subsets are a superset of all reachable states”
Example:
Entity: Telephone Aspect: Call State
{ { on-hook & idle },{ on-hook & ringing }, { off-hook } }
Context Information: specific state
CI( entity=+4917912345,aspect=callState ) =
{ off-hook }
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What is Context (2/2) ?Definition of Context
“A context is the set of all context information characterizing the entities relevant for a specific task in their relevant aspects”“An entity is relevant for a specific task, if its state is characterized at least concerning one relevant aspect”“An aspect is relevant, if the state with respect to this aspect is accessed during a specific task or the state has any kind of influence on the task”
Example:Task: traveller reaching plane
using public transportRelevant Entities
• traveller• carrier (taxi, train, bus...)• infrastructure (roads...)• plane to reach
Context: all CI of relevant aspects
willingness to spend moneyduration/delay, costdelaytime of departure + buffer
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Context Awareness
Definition of Context Awareness:“A system is context aware if it uses any kind of context information before or during service provisioning or service usage”
Location Awareness is special issue of Context Awareness(but by far not the only one!)
Two main benefits from Context Awareness:Adaptation of services to changes in environmentreduces amount of interaction with userImprovement of UI (particularly on small mobile devices)
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Context: Why own interoperability level?
Service Interoperability
SignatureLevel
ProtocolLevel
SemanticLevel
ContextLevel
eases separation of services which are interoperable on classic levels, but not on context level (and vice versa)
Example: electronic public transport timetable service
context is not covered very well in classic levels
enables thematic concentration for correctness and integrity
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Interoperability in MiddlewareMiddleware Task:
Interoperability Evaluation during Service Discoveryservice search (feed)service selection (feed back)
Interoperability Evaluation during Service Executionlifecycle monitoring and managementnotification about and adaptation to context changesinter-provider handover
service A
service B
serviceclient substitutable by
compatible with
compatible with
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MNM Service Model: Service View
service provider domain
customer domain
implements realizes observes implementsrealizes
supplies
accesses
usesserviceclient
supplies
uses
concludes
substantiates
concludes
usagefunctionality
managementfunctionality
QoSparameters
serviceaccess point
service
CSMclientcustomer
«role»user
«role»
provides
service implementation manages
directs
«role»service provider
service management implementation
serviceagreement
Sour
ce: G
arsc
hham
mer
, M.,
Hau
ck, R
., H
eger
ing,
H.-G
., Ke
mpt
er, B
., R
adis
ic, I
., R
ölle
, H.,
Schm
idt,
H.,
A C
ase-
Driv
en M
etho
dolo
gy fo
r App
lyin
g th
e M
NM
Ser
vice
M
odel
, In
Stad
ler,
R.,
Ule
ma,
M.,
edito
rs, P
roce
edin
gs o
f the
8th
Inte
rnat
iona
l IF
IP/IE
EE N
etw
ork
Ope
ratio
ns a
nd M
anag
emen
t Sym
posi
um (N
OM
S 20
02),
pp.
697-
710,
IEEE
Pub
lishi
ng, I
FIP/
IEEE
, Flo
renc
e, It
aly,
Apr
il, 2
002.
CSMaccess point
uses manages accesses
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protocol level
semantic level signature level
context level
context level
signature level semantic level
context level
protocol level
signature level
service provider domain
customer domain
uses manages
implements realizes observes implementsrealizes
supplies
accesses
usesserviceclient
supplies
accesses
uses
concludes
substantiates
concludes
usagefunctionality
managementfunctionality
cont
ext p
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context
uses
CMaccess point
uses
accesses
impl
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prov
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cont
ext i
nfor
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man
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cont
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cont
ext p
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conc
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awareness
supplies
accesses
real
izes
serviceaccess point
service
CSMclientcustomer
«role»CMclientuser
«role»
CSMaccess point
provides
service implementation manages
directs
«role»service provider
usesCMclient
service management implementation
serviceagreement
QoSparameters
Interoperability in Extended MNM S-Model
Context Ontology Language
serv
ice
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Design of Context Ontology Language (CoOL)XML & XML schema based
probably based also on RDF
used to model aspects defining valid context informationrelevance conditionsactors and dependencies
enables dynamic (at runtime) multi-party service interoperability checks at new context levelCoOL is employed during service discovery and execution to negotiate and monitor context to enable context awareness of middleware and services
Middleware uses CoOL statements to link distributed object-associated context information with context un-aware objects and services
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Open issues: Current Investigations on CoOL
Pure XML schema vs. RDF / RDF Schemacomplexity of RDF/RDFS vs. resource limited devicessome drawbacks of RDF have already been identifiede.g. in [Haustein2001] [Furche2001] [Indulska2003]but significant body of work has been done with RDF
“Plugin Model” to DAML-S vs. Standalone ModelDAML-S / DAML+OIL adds additional complexity
WebOnt (OWL) vs. minimum languageOWL in very early state
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Summary
New context level of service interoperabilityadvantages particularly in Ubiquitous Computing Environments
Clear definitions what context is and what notIntroduction of the aspectaffiliated context awarenessExamples
Context extension of the MNM service modelIdentification of interoperability requirements
Outline of Context Ontology Language (CoOL)still some major open issues
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Thank You!
Any Questions?
Dipl.-Inform. Thomas Strangmailto:[email protected] http://www.dlr.de/kn/kn-s/strang
German Aerospace Center (DLR)Site OberpfaffenhofenInstitute of Communications and Navigation (KN-S)PO Box 111682230 Wessling-OberpfaffenhofenTel: +49-8153-28-1354 Fax: +49-8153-28-1871
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Project