1. A. Bucchiarone / Pisa/ 30 Jan 2007 Dynamic Software Architectures for Global Computing Antonio Bucchiarone PhD Student – IMT Graduate School Piazza S. Ponziano, 55100 Lucca (Italy)

2. A. Bucchiarone / Pisa/ 30 Jan 2007 Agenda  Global Computing Systems  Starting Point  SA for Global Computing Systems  Validation and Verification of SA  Current Point  Service-Oriented Computing (SOC)  Service Composition and Evolution  Dynamic Software Architecture (DSA) oriented approach  Main Issues for the future

3. A. Bucchiarone / Pisa/ 30 Jan 2007 Global Computing (GC) Systems  Autonomous computational entities where activity is not centrally controlled (global services)  The entities are created or controlled by different owners  The system is open to the introduction of new computational entities, the behavior may vary over time (dynamic systems)  The offer is expected to evolve from relatively simple (customer) services to global complex (business) solutions (service-oriented computing).  Evolving systems (dynamicity and adaptability)

4. A. Bucchiarone / Pisa/ 30 Jan 2007 Starting Point  To develop an architecture-centric approach for the modeling and validation of (GC) Systems  Analysis and Testing  Definition of approaches to analyze the architectural specification against various kinds of properties  Tool Support

5. A. Bucchiarone / Pisa/ 30 Jan 2007 Current Point  Main characteristics of SOA  Service Composition  Industrial and formal approaches comparison  “Dynamicity” in GC systems  Dynamic Software Architecture (DSA) oriented approach

6. A. Bucchiarone / Pisa/ 30 Jan 2007 Service Oriented Computing  Services as fundamental elements for developing applications  SOC relies on Service-Oriented Architecture (SOA)  SOA is a kind of SA in the context of WSs  This model involves three indispensable participants  Service Provider, Service registry and Service requestor

7. A. Bucchiarone / Pisa/ 30 Jan 2007 Service Composition - I  It combines existing services following a certain pattern to form a new service.  Web Service Composition Approaches: From Industrial Standards to Formal Methods [ICIW’07].  Syntactic WS Composition  BPEL4WS, WS-CDL  Semantic WS Composition  OWL-S, WSMO  Formal Methods for WS Composition  Automata, Petri Nets, Process Algebras

8. A. Bucchiarone / Pisa/ 30 Jan 2007 Service Composition - II  Neither of these approaches offer any direct support for the verification of WS compositions at design-time.  Lack of software tools to verify the correctness of WS compositions

9. A. Bucchiarone / Pisa/ 30 Jan 2007 Service Composition - III  Automata  I/O automata, timed automata, team automata  A lot of framework to analyze and verify properties of WS composition of BPEL processes  From BPEL to automata (SPIN and LTL properties)  From WS-CDL to timed automata (UPPAAL MC)  Petri Nets  BPEL control-flow constructs into labeled PNs  BPEL2PN automatic transformation of BPEL processes in PNs  Process Algebras  Π-calculus, LOTOS,..to describe, compose and verify WSs

10. A. Bucchiarone / Pisa/ 30 Jan 2007 From SA to SOA  SA is intended to describe the structure of a system  Interactions of Computational components  Patterns that guide their composition and constraints on these patterns  SOA  Services as fundamental elements for developing applications  SOA should support evolution during runtime for adapting to changes of environment and requirements  Service Composition combines existing services following a certain pattern to form a new value-added service  Support for “dynamism” of SOA is fundamental to its evolution

11. A. Bucchiarone / Pisa/ 30 Jan 2007 Dynamisms in SA

12. A. Bucchiarone / Pisa/ 30 Jan 2007 Formal Definition of Dynamicity  Hypergraph that describes a style (or meta- model)  Components and Connectors are hyperedges  Component exposes different ports  Connector has tentacles to the ports  Ports are nodes

13. A. Bucchiarone / Pisa/ 30 Jan 2007 Formal Definition of Dynamicity  a style  a configuration  a rewriting production

14. A. Bucchiarone / Pisa/ 30 Jan 2007 Formal Definition of Dynamicity  The set R(G) of reachable configurations, i.e., all configurations to which the initial configuration G in can evolve.  The set D(G) of desirable configurations, i.e., the set of all T-typed configurations that satisfies a desired property p.

15. A. Bucchiarone / Pisa/ 30 Jan 2007 Programmed dynamism  All architectural changes are identified at design-time and triggered by the system itself  A programmed DSA is associated with a grammar G A =  T stands for the style of the architecture  G in is the initial configuration  P is a set of productions gives the evolution of the architecture  D p (G) = R(G)

16. A. Bucchiarone / Pisa/ 30 Jan 2007 Ad-hoc dynamism  All architectural changes are established by the user at unpredictable run-time.  An ad-hoc DSA is associated with a typed grammar G A =  T ah is a graph that contains an infinite number of components and connectors  The initial graph G in is any T ah -typed hypergraph that describe a configuration  The set of production P ah is infinite  They can be the combination of add/remove components and add/remove connectors actions

17. A. Bucchiarone / Pisa/ 30 Jan 2007 Constructible dynamism  All architectural changes are identified at run-time and triggered by the user.  It is similar to ad-hoc but the rewriting productions are not the free combination of basic primitives  G A =  T ah and G in are as ad-hoc dynamism  L c is a language for writing reconfiguration programs  P L c is the set of all valid reconfiguration programs that can be written in L c

18. A. Bucchiarone / Pisa/ 30 Jan 2007 Repairing dynamism  Repairing systems are equipped with a mechanism that monitors the system behavior.  G A =  P = P pgm U P env U P rpr  P pgm describe the normal, ideal behavior of the architecture  P env model the einvironment  “ the communication among components may be lost”  “ a non authorized connector become attached to a particular component”  P rpr indicate the way in which an undesirable configuration can be repaired in order to become a valid one

19. A. Bucchiarone / Pisa/ 30 Jan 2007 Car Assistance Example - I  Components:  Vehicle (V): responsible for transmitting messages destined to the assistant server.  Accident Assistant Server (S): handles help requests  Connectors:  (V/V) : used for mediating the communication between two vehicles (V1/V2)  (V/S) : used for supporting the interaction between a vehicle and a server (V1/S) SV1V1 V2V2 V 1 /S V 1 /V 2

20. A. Bucchiarone / Pisa/ 30 Jan 2007 Car Assistance Example –II Architectural Style An instance

21. A. Bucchiarone / Pisa/ 30 Jan 2007 Programmed Dynamism Architectural Style New vehicle connected to the server Vehicles approximation Initial configuration

22. A. Bucchiarone / Pisa/ 30 Jan 2007 A comparison  “When” the changes are defined  “Who” monitors and triggers the reconfiguration  Flexibility degree

23. A. Bucchiarone / Pisa/ 30 Jan 2007 Main Issues for the Future  High-level modeling of dynamic and service-oriented systems  Compare SMRL and UML profiles defined in Sensoria w.r.t. the WS Composition Characteristics  To understand what kinds of dynamicity they are able to specify  To use them to model the scenarios of Sensoria  Model Transformation  To implement some approach to map high-level models to languages used for verification using methods like MDD  Verification Methods  To adapt the approaches already proposed in the field of SA for the SOA (or DSA)  To verify properties of interest in GC  Consistency and Correctness of orchestrations and choreographies,  Exception Handling and Compensation  QoS

24. A. Bucchiarone / Pisa/ 30 Jan 2007 Questions? antonio.bucchiarone@imtlucca.it