1,522 research outputs found
Behavioral types in programming languages
A recent trend in programming language research is to use behav- ioral type theory to ensure various correctness properties of large- scale, communication-intensive systems. Behavioral types encompass concepts such as interfaces, communication protocols, contracts, and choreography. The successful application of behavioral types requires a solid understanding of several practical aspects, from their represen- tation in a concrete programming language, to their integration with other programming constructs such as methods and functions, to de- sign and monitoring methodologies that take behaviors into account. This survey provides an overview of the state of the art of these aspects, which we summarize as the pragmatics of behavioral types
Real-World Choreographies
Choreographies are a relatively new tool for designing distributed systems from a global viewpoint. Moreover, choreographies are also free from deadlocks and race conditions by design. Recent theoretical results defined proper Endpoint Projection (EPP) functions to compile choreographic specifications into their single components. Since EPPs are behavioural preserving, projected systems also enjoy freedom from deadlocks and races by construction.
Aim of this PhD is to formalise non-trivial features of distributed systems with choreographies and to translate our theoretical results into the practice of implemented systems. To this purpose, we provide two main contributions.
The first contribution tackles one of the most challenging features of distributed development: programming correct and consistent runtime updates of distributed systems. Our solution is a theoretical model of dynamic choreographies that provides a clear definition of which components and behaviours can be updated. We prove that compiled choreographic specifications are correct and consistent after any update. We also refine our theoretical model to provide a finer control over updates. On this refinement, we develop a framework for programming adaptable distributed systems.
The second contribution covers one of the main issues of implementing theoretical results on choreographies: formalising the compilation from choreographies to executable programs. There is a sensible departure between the present choreographic frameworks and their theoretical models because their theories abstract communications with synchronisation on names (a la CCS/Ï-calculus) yet they compile to Jolie programs, an executable language that uses correlation â a renown technology of Service-Oriented Computing â for message routing. Our solution is a theory of Applied Choreographies (AC) that models correlation-based message passing. We pinpoint the key theoretical problems and formalise the principles that developers should follow to obtain correct implementations. Finally, we prove our approach by defining a correct compiler from AC to the calculus behind the Jolie language
Modeling and verification of web service composition based interorganizational workflows
Interorganisationale Workflows sind ArbeitsablĂ€ufe, welche die Grenzen einer Organisation verlassen und einen Rahmen fĂŒr Kooperationen der verschiedenen autonomen Organisationen zur VerfĂŒgung stellen. Ein wichtiger Punkt fĂŒr den Entwurf solcher Workflows ist die Balance zwischen Offenheit und Abgrenzung, wobei erstere fĂŒr Kooperationen und letztere die fĂŒr den Schutz von Know-how benötigt wird. Workflow Sichten stellen ein effizientes Werkzeug fĂŒr diesen Zweck zur VerfĂŒgung. Durch Offenlegung von bestimmten Teilen eines Prozesses, können Organisationen sowohl kooperieren als auch das Know-how schĂŒtzen. Diese Dissertation prĂ€sentiert nun eine Methode fĂŒr die korrekte Konstruktion von Workflow Sichten.
Es wird angenommen, dass Organisationen Web Service orientierte Technologien zur Modellierung und Implementierung von interorganisationalen Workflows verwenden. Die Anwendung von Web Services bietet Organisationen viele Vorteile. Den eigentlichen Mehrwert von Web Services stellt aber die KompositionsfĂ€higkeit dar. VerfĂŒgbare Web Services können dadurch von anderen Choreographien und Orchestrationen (wieder-)verwendet werden. Die Notwendigkeit der Implementierung von Systemen von Null weg kann minimiert werden. Die zentralen Anforderungen sind einerseits eine Architektur mit adĂ€quatem Potential, andererseits die Verifikation der Korrektheit.
Diese Dissertation prĂ€sentiert nun eine Architektur zur Modellierung von Web Service Composition basierten interorganisationalen Workflows, genannt föderierte Choreographien, die verglichen mit anderen Architekturen verschiedene Vorteile anbieten. DarĂŒber hinaus werden Algorithmen und Techniken zur Verifikation der strukturellen und temporalen Korrektheit vorgestellt. Strukturelle Korrektheit prĂŒft, ob die Strukturen der beteiligten Prozesse zusammenpassen. Temporale Korrektheit ĂŒberprĂŒft, ob ein interorganisationaler Workflow, der aus mehreren Choreographien und Orchestrationen besteht hinsichtlich der lokalen und globalen Bedingungen fehlerfrei ist. Mit Hilfe dieser Techniken kann die strukturelle und temporale KonformitĂ€t des Modells zur Designzeit ĂŒberprĂŒft werden. Falls das Modell nicht strukturell oder temporal konform ist, können nötige Ănderungen durchgefĂŒhrt werden, sodass die korrekte AusfĂŒhrung zur Laufzeit garantiert werden kann. Die ĂberprĂŒfung der KonformitĂ€t zur Designzeit reduziert die Prozesskosten vor allem wegen den folgenden zwei GrĂŒnden: Erstens, die entdeckten Fehler zur Designzeit sind normalerweise billiger als jene, die zur Laufzeit entdeckt werden und zweitens, Fehlerbehandlungsmechanismen können verhindert werden, die wiederum Zusatzkosten verursachen. ZusĂ€tzlich zu der vorgestellten Architektur wird eine allgemeinere Architektur zusammen mit den passenden KonformitĂ€tsprĂŒfungsalgorithmen prĂ€sentiert. Der Ansatz ist Platform- und sprachunabhĂ€ngig und die Algorithmen sind verteilt.Interorganizational workflows are workflows that cross the
boundaries of a single organization and provide a framework for
cooperation of different autonomous organizations. An important
issue when designing such workflows is the balance between the
openness needed for cooperation and the privacy needed for
protection of business know-how. Workflow views provide an efficient
tool for this aim. By exposure of only selected parts of a process,
organizations can both cooperate and protect their business logic.
This dissertation presents a technique for a correct construction of
workflow views.
It is assumed that organizations and partners use web services and
web service related technology to model and implement
interorganizational workflows. Application of web services offers
several advantages for organizations. The real surplus of web
services is their capability of being composed to more complex
systems. Available web services can be reused by other
choreographies and orchestrations and the need for development of
new systems from scratch can be minimized. The essential
requirements are on the one hand an architecture with adequate
capabilities and on the other hand, verification of correctness.
This dissertation proposes an architecture for modeling web service
composition based interorganizational workflows, called
\emph{federated choreographies}, that provides several advantages
compared to existing proposals. Moreover, algorithms and techniques
for verification of structural and temporal correctness of
interorganizational workflows are proposed. Structural conformance
checks if the structures of the involved processes match. Temporal
conformance checks if an interorganizational workflow composed of
choreographies and orchestrations is temporally error-free with
respect to local and global temporal constraints. The proposed
algorithms can be applied for checking the structural and temporal
conformance of the federated choreographies at design-time. If the
model is not structurally or temporally conformant, necessary
modifications can be done such that the correct execution of the
flow at run-time can be guaranteed. The conformance checking at
design time reduces the cost of process because of two reasons:
first, errors detected at design time are normally cheaper than
those detected at run time and second, exception handling mechanisms
can be avoided which are, in turn, coupled with additional costs. In
addition to the proposed architecture, a more general architecture
together with the conformance checking algorithms and techniques for
interorganizational workflows are presented. The presented approach
is language and platform independent and algorithms work in a
distributed manner
Service discovery and negotiation with COWS
To provide formal foundations to current (web) services technologies, we put forward using COWS, a process calculus for specifying, combining and analysing services, as a uniform formalism for modelling all the relevant phases of the life cycle of service-oriented applications, such as publication, discovery, negotiation, deployment and execution. In this paper, we show that constraints and operations on them can be smoothly incorporated in COWS, and propose a disciplined way to model multisets of constraints and to manipulate them through appropriate interaction protocols. Therefore, we demonstrate that also QoS requirement specifications and SLA achievements, and the phases of dynamic service discovery and negotiation can be comfortably modelled in COWS. We illustrate our approach through a scenario for a service-based web hosting provider
The CHORCH Approach: How to Model B2Bi Choreographies for Orchestration Execution
The establishment and implementation of cross-organizational business processes is an implication of today's market pressure for efficiency gains.
In this context, Business-To-Business integration (B2Bi) focuses on the information integration aspects of business processes.
A core task of B2Bi is providing adequate models that capture the message exchanges between integration partners.
Following the terminology used in the SOA domain, such models will be called choreographies in the context of this work.
Despite the enormous economic importance of B2Bi, existing choreography languages fall short of fulfilling all relevant
requirements of B2Bi scenarios.
Dedicated B2Bi choreography standards allow for inconsistent outcomes of basic interactions and
do not provide unambiguous semantics for advanced interaction models.
In contrast to this, more formal or technical choreography languages may provide unambiguous modeling semantics,
but do not offer B2Bi domain concepts or an adequate level of abstraction.
Defining valid and complete B2Bi choreography models becomes a challenging task in the face of these shortcomings.
At the same time, invalid or underspecified choreography definitions are particularly costly considering the organizational
setting of B2Bi scenarios.
Models are not only needed to bridge the typical gap between business and IT,
but also as negotiation means among the business users of the integration partners on the one hand
and among the IT experts of the integration partners on the other.
Misunderstandings between any two negotiation partners potentially affect the agreements between all other negotiation partners.
The CHORCH approach offers tailored support for B2Bi by combining the strengths of both dedicated B2Bi standards and formal rigor.
As choreography specification format, the ebXML Business Process Specification Schema (ebBP) standard is used.
ebBP provides dedicated B2Bi domain concepts such as so-called BusinessTransactions (BTs) that abstractly specify the exchange of a request business document
and an optional response business document.
In addition, ebBP provides a format for specifying the sequence of BT executions for capturing complex interaction scenarios.
CHORCH improves the offering of ebBP in several ways.
Firstly, the execution model of BTs which allows for inconsistent outcomes among the integration partners
is redefined such that only consistent outcomes are possible.
Secondly, two binary choreography styles are defined as B2Bi implementation contract format in order to streamline implementation projects.
Both choreography styles are formalized and provided with a formal execution semantics for ensuring unambiguity.
In addition, validity criteria are defined that ensure implementability using BPEL-based orchestrations.
Thirdly, the analysis of the synchronization dependencies of complex B2Bi scenarios is supported
by means of a multi-party choreography style combined with an analysis framework.
This choreography style also is formalized and standard state machine semantics are reused in order to ensure unambiguity.
Moreover, validity criteria are defined that allow for analyzing corresponding models for typical multi-party choreography issues.
Altogether, CHORCH provides choreography styles that are B2Bi adequate, simple, unambiguous, and implementable.
The choreography styles are B2Bi adequate in providing B2Bi domain concepts, in abstracting from low-level implementation details
and in covering the majority of real-world B2Bi scenarios.
Simplicity is fostered by using state machines as underlying specification paradigm.
This allows for thinking in the states of a B2Bi scenario and for simple control flow structures.
Unambiguity is provided by formal execution semantics whereas implementability (for the binary choreography styles) is ensured by providing
mapping rules to BPEL-based implementations.
The validation of CHORCH's choreography styles is performed in a twofold way.
Firstly, the implementation of the binary choreography styles based on Web Services and BPEL technology is demonstrated
which proves implementability using relatively low-cost technologies.
Moreover, the analysis algorithms for the multi-party choreography styles are validated using a Java-based prototype.
Secondly, an abstract visualization of the choreography styles based on BPMN is provided that abstracts from
the technicalities of the ebBP standard.
This proves the amenability of CHORCH to development methods that start out with visual models.
CHORCH defines how to use BPMN choreographies for the purpose of B2Bi choreography modeling
and translates the formal rules for choreography validity into simple composition rules that
demonstrate valid ways of connecting the respective modeling constructs.
In summary, CHORCH allows integration partners to start out with a high-level visual model of their interactions in BPMN
that identifies the types and sequences of the BusinessTransactions to be used.
For multi-party choreographies, a framework for analyzing synchronization dependencies then is available.
For binary choreographies, an ebBP refinement can be derived that fills in the technical parameters that are needed for deriving the implementation.
Finally, Web Services and BPEL based implementations can be generated.
Thus, CHORCH allows for stepwise closing the semantic gap between the information perspective of business process models
and the corresponding implementations.
It is noteworthy that CHORCH uses international standards throughout all relevant layers, i.e., BPMN, ebBP, Web Services and BPEL,
which helps in bridging the heterogeneous IT landscapes of B2Bi partners.
In addition, the adoption of core CHORCH deliverables as international standards of the RosettaNet community
give testament to the practical relevance and promise dissemination throughout the B2Bi community.BetriebsĂŒbergreifende GeschĂ€ftsprozessintegration ist eine logische Konsequenz allgegenwĂ€rtigen Wettbewerbsdrucks.
In diesem Kontext fokussiert Business-To-Business integration (B2Bi) auf die
Informationsaustausche zwischen Unternehmen.
Eine B2Bi-Kernanforderung ist die Bereitstellung adÀquater Modelle zur Spezifikation der Nachrichtenaustausche zwischen Integrationspartnern.
Diese werden im Rahmen dieser Arbeit in Anlehnung an Service-orientierte Architekturen (SOA)-Terminologie Choreographien genannt.
Bestehende Choreographiesprachen decken die Anforderungen an B2Bi-Choreographien nicht vollstÀndig ab.
Dedizierte B2Bi-Choreographiestandards definieren inkonsistente Austauschprozeduren fĂŒr grundlegende Interaktionen
und nur unvollstĂ€ndige Semantiken fĂŒr fortgeschrittene Interaktionen.
Formale oder Technik-getriebene Choreographiesprachen bieten die benötigte PrÀzision,
lassen aber DomÀnenkonzepte vermissen oder operieren auf einer niedrigen Abstraktionsebene.
Angesichts solcher MÀngel wird die Spezifikation valider und vollstÀndiger B2Bi-Choreographien zu einer echten Herausforderung.
Gleichzeitig sind mangelhafte Choreographiemodelle gerade im B2Bi-Bereich besonders problematisch,
da diese nicht nur zwischen Fach- und IT-Abteilung, sondern auch ĂŒber Unternehmensgrenzen hinweg eingesetzt werden.
Der CHORCH-Ansatz schafft an dieser Stelle mittels maĂgeschneiderter Choreographien Abhilfe,
welche die Vorteile von B2Bi-Choreographien und von formalen AnsÀtzen kombinieren.
Als Ausgangspunkt wird das ebXML Business Process Specification Schema (ebBP) verwendet,
das als B2Bi-Choreographiestandard DomÀnenkonzepte wie zum Beispiel
sogenannte BusinessTransactions (BTs) bietet.
Eine BT ist der Basisbaustein von B2Bi-Choreographien und spezifiziert
den Austausch eines GeschÀftsdokuments sowie eines optionalen Antwortdokuments.
DarĂŒber hinaus bietet ebBP ein Format zur Spezifikation von BT-Kompositionen zur UnterstĂŒtzung komplexer Interaktionen.
CHORCH erweitert ebBP wie folgt.
Erstens, das AusfĂŒhrungsmodell fĂŒr BTs wird neu definiert, um inkonsistente ErgebniszustĂ€nde zu eliminieren.
Zweitens, fĂŒr Entwicklungsprojekte werden zwei binĂ€re Choreographieklassen definiert, die als B2Bi-Implementierungskontrakt dienen sollen.
Die Formalisierung beider Klassen sowie formale operationale Semantiken gewÀhrleisten Eindeutigkeit,
wĂ€hrend ValiditĂ€tskriterien die AusfĂŒhrbarkeit entsprechender Modelle mittels BPEL-basierter Orchestrationen garantieren.
Drittens, zur Analyse der Synchronisationsbeziehungen komplexer B2Bi-Szenarien wird eine Multi-Party-Choreographieklasse nebst Analyseframework definiert.
Wiederum wird fĂŒr diese Klasse eine Formalisierung definiert, die mittels Standard-Zustandsautomatensemantik Eindeutigkeit gewĂ€hrleistet.
Ferner garantieren ValiditÀtskriterien die Anwendbarkeit der definierten Analysealgorithmen.
Insgesamt bieten die Choreographieklassen des CHORCH-Ansatzes ein B2Bi-adÀquates, einfaches, eindeutiges und implementierbares
Modell der Nachrichtenaustausche zwischen B2Bi-Partnern.
B2Bi-AdÀquatheit wird durch Verwendung von B2Bi-DomÀnenkonzepten, Abstraktion von rein technischen Kommunikationsdetails
und Abdeckung der meisten praktisch relevanten B2Bi-Szenarien gewÀhrleistet.
Einfachheit ist ein Ausfluss der Verwendung eines Zustandsmaschinen-basierten Modellierungsparadigmas,
das die Definition des Interaktionsfortschritts in Form von ZustÀnden sowie einfache Kontrollflussstrukturen ermöglicht.
Eindeutigkeit wird durch die Verwendung formaler Semantiken garantiert, wĂ€hrend Implementierbarkeit (fĂŒr die beiden binĂ€ren Choreographieklassen)
durch Angabe von Mapping-Regeln auf BPEL-Orchestrationen sichergestellt wird.
Die Validierung der CHORCH-Choreographieklassen erfolgt in zweierlei Hinsicht.
Erstens, die Implementierbarkeit der binÀren Choreographieklassen mit Hilfe von Web Services und BPEL wird durch die Definition entsprechender
Mappingregeln belegt. Weiterhin wird das Analyseframework der Multi-Party-Choreographieklasse als Java-Prototyp implementiert.
Zweitens, fĂŒr alle Choreographieklassen wird eine abstrakte Visualisierung auf BPMN-Basis definiert, die von diversen technischen Parametern
des ebBP-Formats abstrahiert.
Damit wird die Integrierbarkeit der CHORCH-Choreographieklassen in EntwicklungsansÀtze,
die ein visuelles Modell als Ausgangspunkt vorsehen, belegt.
CHORCH definiert, wie sogenannte BPMN-Choreographien zum Zweck der B2Bi-Choreographiemodellierung zu verwenden sind
und ĂŒbersetzt die ValiditĂ€tskriterien der CHORCH-Choreographieklassen in einfache Modell-Kompositionsregeln.
In seiner Gesamtheit bietet CHORCH somit einen Ansatz, mit Hilfe dessen B2Bi-Partner zunÀchst
die Typen und zulÀssigen Reihenfolgen ihrer GeschÀftsdokumentaustausche auf Basis eines abstrakten visuellen BPMN-Modells identifizieren können.
Im Fall von Multi-Party-Choreographien steht dann ein Framework zur Analyse der Synchronisationsbeziehungen zwischen den Integrationspartnern zur VerfĂŒgung.
Im Fall von binÀren Choreographien können ebBP-Verfeinerungen abgeleitet werden, welche die Modelle um technische Parameter anreichern, die zur Ableitung
einer Implementierung benötigt werden. Diese ebBP-Modelle sind in Web Services- und BPEL-basierte Implementierungen ĂŒbersetzbar.
Damit erlaubt CHORCH die schrittweise ĂberbrĂŒckung der semantischen LĂŒcke zwischen der Informationsaustauschperspektive von
GeschÀftsprozessmodellen und den zugehörigen Implementierungen.
Ein beachtenswerter Aspekt des CHORCH-Ansatzes ist die Verwendung einschlÀgiger internationaler Standards auf allen Abstraktionsebenen,
im Einzelnen BPMN, ebBP, Web Services und BPEL. Die Verwendung von Standards trÀgt dem heterogenen Umfeld von B2Bi-Szenarien Rechnung.
ZusÀtzlich wurden Kernergebnisse des CHORCH-Ansatzes als internationale Standards der RosettaNet-B2Bi-Community veröffentlicht.
Dies belegt die praktische Relevanz des Ansatzes und fördert die Verbreitung innerhalb der B2Bi-Community
Using Web services choreography to support an extensible and flexible system development process
Systems Engineering (SE) controls a complex environment consisting of various collaborative subsystems. Each subsystem demands different kind of requirements and follows a specific strategy for its development process. Unifying and harmonizing the development process of all collaborative subsystems towards achieving the ultimate integrated system is one of the main challenges of SE. This work introduces a new approach towards having a generic SE unified process applicable to various environments. We suggest a service-oriented framework for SE process implemented using Web Services, and describe the process scenario in a machine-friendly abstract layer over the Development Process. This description layer choreographs collaborative subsystems and is implemented by a Web Services Choreography Description Language (WSCDL). It also covers Interface Management concerns of SE. In such an environment, as long as all services follow a unique framework for the SE process such as the one specified by the International Council on Systems Engineering (INCOSE), each phase of the process would then be an anonymous service implemented by a different vendor. As the result, an organization could easily customize its own specific development environment by editing this choreography layer according to its specific development policies, and then tailor its own desired development environment by choosing and integrating various services available on the Web. Source: Masters Abstracts International, Volume: 45-01, page: 0351. Thesis (M.Sc.)--University of Windsor (Canada), 2006
Using Web services choreography to model business process in e-commerce
Web modeling languages like WebML (Web modeling Language), OOHDM (Object Oriented Hypermedia design) are evolved from hypermedia models. And they pay attention only to hypermedia modeling and model business rules as a form of navigation, this is called business process emulation. Our approach is to use web service peer-peer language, such as WS-CDL to model business process in an e-commerce application. In this way we introduce a new layer that models all the business rules using WS-CDL In this approach the hypermedia model models only navigation using WebML and once business process is initiated from simple navigation the process layer defined using WS-CDL will execute the business rules. By constructing a case study to test this hybrid-modeling framework, we hypothesise that this newly released peer-peer collaborative language for web-services can be used to model the concepts of business process. Thus we get a unique approach to model business process along with navigation. This approach is a proposed solution to the issues of business process emulation. Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis2006 .S86. Source: Masters Abstracts International, Volume: 45-01, page: 0366. Thesis (M.Sc.)--University of Windsor (Canada), 2006
- âŠ