Architecture Centric Development PPT Presentation

1. π-Method: A Model-Driven
Formal Method for Architecture-
Centric Software Engineering
By Flavio Oquendo
Presented by: Sajith Wickramaratne

2. π-Method
 This article presents the π-Method, a formal method that has been designed
in the ArchWare European Project to address model-driven development of
safe software systems.
 It is a well-defined theoretical method relying on formal foundations.
 It supports formal model-driven development of software systems having
highly dynamic architectures.
 Its formal language for architecture is based on:
Architecture description : π-calculus.
Architecture analysis : μ-calculus.
Architecture transformation and refinement: Rewriting logic.

3. π-Method vs. Other formal methods
 Formal methods such as B, FOCUS, VDM, and Z, aim
to provide full support for formal development of
software systems.
 However, these methods do not provide any
architectural support.
 π-Method has been built from scratch to formally
support architecture-centric component-based model-
driven development.

4. Completeness and Correctness of
Software Systems
 Support the formal specification of software systems whose
architecture can change (at run-time).
 Support automated analysis: functional as well as non-functional
properties.
 Support their transformations and application synthesis, by
stepwise refinement from abstract to concrete specifications and
full code generation.
 Support compliance with respect to application requirements (if
requirements change, enable the software system to safely
progress with new requirements).

5. π-Method
 Why Formal?
 Improves documentation and understanding of
specifications.
 Enables rigorous analysis of the system
properties.
 Improves rigour and quality of the whole
development process.
 Provides a firm foundation during the evolution
process.

6. π-Method
Why Architecture-Centric?
 A key aspect of the design of any software system is its architecture.
 Fundamental organization of the system embodied in its components, their
relationships to each other, and to the environment, and the principles
guiding its design and evolution.
 Provides the conceptual abstraction for modeling complex software systems
during development and then during deployment and evolution
Why Model-Driven Engineering?
 Models are used to understand specific system aspects.
 Predicts system qualities.
 Reasons about impact of changes.
 Indicates major system features to stakeholders.

7. Approach of the π-Method
 The novelty of the π-Method lies in its holistic view of formal software
development.
 It involves:
“how” the software is to function in terms of expected behaviours.
“what” is its structure in terms of components and their connectors.
“which” qualities are to be guaranteed.
 Furthermore, an appropriate refinement process (describing “how to build”
the software).

8. Architecture-centric formal development

9. Architecture-centric formal development
“Define style” activities:
 Principal actors are the “style architects”.
 Represent the top level inception of a family of software architectures.
 What types of architectural elements.
 How elements can be combined.
 Which constraints apply, and which processes can be applied to architecture elements
and whole architecture descriptions.
“Describe architecture” activities:
 Principal actors are the “application architects”.
 Use the domain specific styles defined by the style architect to describe a specific
software architecture.
 An architecture description, in terms of a model.
 Can represent a system at various levels of abstractions.
“Refine architecture” activities:
 Principal actors are the “application engineers”.
 Support transformations from abstract to more concrete architecture descriptions.
 Derive concrete models by applying correctness preserving transformations.

10. Model transformations with π-ARL

11. Formal Languages
 π-ADL: an architecture description language based on
the higher-order typed π-calculus.
 π-AAL: an architecture analysis language based on the
μ-calculus.
 π-ARL: an architecture refinement language based on
the rewriting logic.

12. The triad of formal languages

13. The Architecture Description Language:
π-ADL
 Architecture Description Language encompasses two aspects: expression and
verification of architectural styles.
 General principles guided the design of π-ADL:
 Formality: π-ADL (formal language) provides a formal system, at the
mathematical sense, for describing dynamic software architectures.
 Run-time viewpoint: π-ADL focuses on the formal description of software
architectures from the run-time viewpoint: structure, behavior, and how these may
evolve over time.
 Executability: π-ADL(executable language) is a virtual machine that runs
specifications of software architectures.
 User-friendliness: π-ADL supports different concrete syntaxes – textual and
graphical notations (including UML-based) .

14. π-ADL
Design principles
 The principle of correspondence.
 The principle of abstraction.
 The principle of data type completeness.
Civil rights in the language
 The right to be declared.
 The right to be assigned.
 The right to have equality defined over them.
 The right to persist.

15. The Architecture Analysis Language:
π-AAL
Architecture Analysis Language focuses two aspects:
 Architectural styles (style architects)
 Software Architectures (application architects).
Properties of styles and architectures.
 structural (e.g. cardinality of architectural elements, interconnection topology)
 behavioral (e.g. safety, liveness, and fairness defined on actions of the system).
The π-AAL is a formal property expression language designed to
support automated verification.
 Can mechanically check whether an architecture described in π-ADL satisfies
property expressed in π-AAL.

16. The Architecture Refinement Language:
π-ARL
 The concrete architecture: Vertical and Horizontal transformations.
 Horizontal refinement is obtained from transforming an architecture by partition.
 Vertical refinement is obtained from transforming steps to add more details to abstract
models until the concrete architectural model is described.
 The π-Method (ARL) supports both horizontal and vertical refinements.
 π- ARL’s four forms of refinement from an external or internal point of view:
 behavior refinement
 port refinement
 structure refinement
 data refinement

17. Application domains of the
π-Method
The π-Method (π-ADL, π-AAL, and π-ARL) have been applied in
the following application domains:
• software systems targeting J2EE platforms.
• enterprise application integration systems.
• grid computing systems.
• human-computer interfaces for monitoring systems.
• mobile agent systems.
• sensor-actuator networks.
• service-oriented architectures.
• ambient intelligence.

18. Related Work for π-Method
 Architecture Description (ADLs):
ACME, AESOP,AML,ARMANI,CHAM-ADL, DARWIN,META-
H,PADL,RAPIDE,SADL, σπ-SPACE, UNICON-2,andWRIGHT/Dynamic-
WRIGHT.
 Architecture Analysis (AALs):
PDL, LOTOS, CADP and CCS.
 Architecture Transformation and Refinement(ARLs):
FOCUS,RAPIDE, SADL, B and Z.

19. Future Work in π-Method
 π-Modeller: a tool to support visual description of software architectures in π-ADL
 π-Animator: a tool to support graphical animation of software architectures described
in π-ADL.
 π-Analyser: a tool to support verification of structural and behavioural properties
specified in π-AAL against software architectures described in π-ADL.
 π-Refiner: a tool to support refinements of software architectures described in π-ADL.
 π-Synthesiser: a tool to support code generation from concrete architecture
descriptions in π-ADL.
 π-ADL Compiler and Virtual Machine.
 π-TraceChecker.

20. Conclusion
 π-Method recognizes architecture-centric model-driven
approaches, supported by adequate, compositional,
formal languages and tools.
 It involves π-ADL, π-AAL, and π-ARL to support
architectural description, analysis, refinement, and code
generation.
 π-Method cost-effectively develops and evolves
software systems while guaranteeing their completeness
and correctness.