Ludger Fiege [email protected] joint work with Mira Mezini, Gero Mühl, Alejandro Buchmann Dep. of...

Ludger FiegeLudger Fiege [email protected]

joint work with joint work with Mira Mezini, Gero Mühl, Alejandro BuchmannMira Mezini, Gero Mühl, Alejandro Buchmann

Dep. of Computer ScienceDep. of Computer ScienceTU Darmstadt, GermanyTU Darmstadt, Germany

Visibility as Central Abstraction in Visibility as Central Abstraction in Event-based SystemsEvent-based Systems

Ludger Fiege, [email protected] Darmstadt, Germany

Event-based SystemsEvent-based Systems

Pub/Sub SystemPub/Sub System


BenefitsBenefits

We appreciate the loose couplingWe appreciate the loose coupling– Indirect addressing, space decouplingIndirect addressing, space decoupling– Additional degrees of freedomAdditional degrees of freedom

Basic CS solution…Basic CS solution…

Event-based:Event-based:– Components control their own state, solelyComponents control their own state, solely

IndependenceIndependence ReusabilityReusability


Event-based SystemsEvent-based Systems



DrawbacksDrawbacks

Composed functionality isComposed functionality is– Direct and implicit result of compositionDirect and implicit result of composition– No explicit control of coordinationNo explicit control of coordination

Control only by adapting components:Control only by adapting components:– Tailor event types/contents Tailor event types/contents – Encode application structure into componentsEncode application structure into components

Sacrifice very benefits of event-based style?!Sacrifice very benefits of event-based style?!

Usable as basic programming paradigm?Usable as basic programming paradigm?


Event-based SystemsEvent-based SystemsRegaining ControlRegaining Control



ScopesScopes

Scopes constrain the visibility of notificationsScopes constrain the visibility of notifications– VisibilityVisibility as first-class conceptas first-class concept

Structure not emulated by namespaces or filtersStructure not emulated by namespaces or filters Clients not aware of structureClients not aware of structure

– External control of structure: Integration External control of structure: Integration

Family 1

Ma GrandMa

Family 2

Ma GrandMa

sick sickadviceadvice


Fairytale IIFairytale IIA Scoped World: StructuringA Scoped World: Structuring

Family 1

Forest

Wolf

Grand-mother

Mother

LRRH

Family 2


Fairytale IIIFairytale IIIA Scoped World: Information HidingA Scoped World: Information Hiding

Family 1

Forest

Wolf

Grand-mother

Mother

LRRH

Family 2

advice advice

advice


GermanImmigrants

Pen-friends

Fairytale IVFairytale IVHeterogeneous WorldHeterogeneous World

Family

Forest

Wolf

Grand-mother Mother

LRRH

krank

sick


Fairytale VFairytale VLRRH ServicesLRRH Services

Family 1

Forest

Wolf

Grand-mother

Mother

LRRHServiceDad

Family 2

1 2 3

Default broadcast semantics not always appropriateDefault broadcast semantics not always appropriate

Family 1

Forest

Wolf

Grand-mother

Mother

LRRHServiceDad

Family 2

1 2 3

Default broadcast semantics not always appropriateDefault broadcast semantics not always appropriate


ImplementationImplementation

Project RProject REBECA: EBECA:

http://http://www.gkec.informatik.tu-darmstadt.de/rebecawww.gkec.informatik.tu-darmstadt.de/rebeca

Prototype of notification infrastructurePrototype of notification infrastructure– Scalable content-based filteringScalable content-based filtering– Structuring with ScopesStructuring with Scopes

Example ApplicationsExample Applications– Stock trading platformStock trading platform– Self-actualizing web pagesSelf-actualizing web pages


UMLUML

Component

SimpleComponent Scope

ComponentInterface *

*

2

SessionScope

DeliveryPolicy

SecurityPolicy

EventMappings


Using ScopesUsing Scopes

Different Implementations of ScopesDifferent Implementations of Scopes– Not always all configuration options availableNot always all configuration options available– Adapt/tailored to deployment scenarioAdapt/tailored to deployment scenario

Up to now: SpecificationUp to now: Specification– XML description of interfacesXML description of interfaces– Java objects implementing policiesJava objects implementing policies

Future: Future: – Composition languagesComposition languages– Functional PLFunctional PL


ContributionsContributions

We started by implementing an event-based We started by implementing an event-based middlewaremiddleware

Introduce scopes in event-based systemsIntroduce scopes in event-based systems– first-class structuring mechanismfirst-class structuring mechanism– Obvious benefitsObvious benefits

Control side effectsControl side effects

– Address heterogeneity issuesAddress heterogeneity issues– Refine event service semanticsRefine event service semantics


……and thenand then

Event-based componentsEvent-based components– Information hidingInformation hiding– Composing new componentsComposing new components

Implemented framework:Implemented framework:– allows to investigate scopes as new abstraction in allows to investigate scopes as new abstraction in

event-based systemsevent-based systems– Software engineeringSoftware engineering

Component languages, Meta Object ProtocolsComponent languages, Meta Object Protocols

– Data managementData management Sessions, transactions, notification lifetimeSessions, transactions, notification lifetime

– Distributed systemsDistributed systems Multicast, ordering, group communicationMulticast, ordering, group communication

– ……


QuestionsQuestions??

Thank you for listening!Thank you for listening!

Ludger FiegeLudger Fiege

Dep. of Computer ScienceDep. of Computer Science

TU Darmstadt, GermanyTU Darmstadt, Germany

[email protected]

Ludger Fiege [email protected] joint work with Mira Mezini, Gero Mühl, Alejandro Buchmann Dep. of...

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