1. Luca Simoncini PDCC, Pisa and University of Pisa, Pisa, Italy
System Architecture and Interoperability - Architecture is a critical element of the solution -
Luca Simoncini
PDCC, Pisa and University of Pisa, Pisa, Italy
Pisa, 25-27/11/02, Workshops on &

2. Pros and cons of present architectural designs
Most of large-scale infrastructures have been developed connecting stand-alone proprietary systems with ad-hoc solutions and independently developed components
Pros:
Ad-hoc components make easier system validation
Limitation of third-party components
Re-design and updating do not depend on third parties
Cons:
Components and implementation technologies evolution and obsolescence
Upgrading of components
Unflexibility and difficult adaptability
Needed re-validation for new systems or major revisions
Cons on interaction and interoperability
Systems with slightly different requirements and specs cannot reuse components from previous designs:
Complete re-design
Lack of experience from older systems
Interoperability is hard to achieve:
Different project specifications
Different dependability properties
Different communication protocols or media
…….
Difficult integration
Pisa, 25-27/11/02, Workshops on &

3. What is needed
Definition and construction of an architectural framework such:
To reduce the design and development costs
To reduce the number of components used in the several subsystems
To simplify the evolution process of the products and reduce the associated costs
To simplify the validation (and certification) of the products through an incremental approach based on reuse
Infrastructure characteristics:
Use of generic components:
COTS and open source SW components
Dependability properties associated to architecture and not only to components:
Techniques for error detection, diagnosis and recovery independent from specific components (both HW or SW)
Hierarchical approach for functional and non functional properties:
To make validation easier
Openness of the system:
Adaptability to different kinds of architecture for interaction.
Pisa, 25-27/11/02, Workshops on &

4. Trends, new problems and keywords
Increasing number of (maybe non-trained) users:
New fault types
New threats (i.e. to privacy and security)
Ubiquity and mobility:
New threats to security
Evolution, growing complexity, layering of services:
Vital services and system survivability
Keywords:
Integration
Composition
Recursion:
fault error failure
Usability
Genericity, Openness, Adaptability, Re-use for:
Design of dependable components and
architectures
Designing architectures for dependability
Dependable infrastructures from user
perspective
Pisa, 25-27/11/02, Workshops on &

5. Design of dependable components and architectures
Architecture is a critical element of the solution
Rigorous design (i.e. fault prevention)
Verification and validation (i.e. fault removal)
Fault Tolerance (accidental and malicious faults)
System evaluation (i.e. fault forecasting)
Requirements
Composable compon.
Secure components
Separation of concern
Invariance
Early prototyping
Adaptable compon.
Testable components
Coverage evaluation
Enabling Technologies
Formal methods
Design for V&V
State observability
Testing
Supports to validation and verification
Redundancy
Functional diversity
Middleware
Analytical modeling
Fault injection
Instruments
Specs languages
Modeling
Tools
Function placement
Generic, composable, open source, reusable components
Pisa, 25-27/11/02, Workshops on &

6. Designing architectures for dependability
Multiple facets of dependability raise many issues
Rigorous design
(i.e. fault prevention)
Verification and validation (i.e. fault removal)
Fault Tolerance (accidental and malicious faults)
System evaluation (i.e fault forecasting)
How to compose:
Interfaces
Legacy systems
How to guarantee integrity
How to guarantee security
How to guarantee survivability
How to guarantee predictable timing
Trusting the tools
Testing
Symbolic execution
How to assess risks
How to cope with new fault types
How to reach survivability
How to coordinate adaptability
How to get good usability
Uncertainty
Meaningful models
Meaningful simulations
Evaluating coverage
Experimental verification
Abstraction, recursion, incremental verification
Pisa, 25-27/11/02, Workshops on &

7. Dependable infrastructures from user perspective
The user has the final word on system dependability
Rigorous design
(i.e. fault prevention)
Verification and validation (i.e. fault removal)
Fault Tolerance (accidental and malicious faults)
System evaluation (i.e. fault forecasting)
Is the system compliant with specifications ?
Do I have the knowledge of possible residual faults ?
Is the system able to provide meaningful service in presence of accidental and malicious faults ?
Has the system sufficient performance to satisfy my needs ?
Is system usability sufficiently good to reduce the probability of human errors ?
Does the system protect my privacy, integrity of my data and and security ?
Is the cost/dependability ratio optimal for my needs ?
I think the system/service has
(optimal/good/sufficient/insufficient) cost/dependability !
Pisa, 25-27/11/02, Workshops on &

8. System architecture in
Application studies | Tools and Components | Support Measures
Aerospace
Healthcare
Dependability
Case Support
Modelling and
simulation
Policy Issues
e-business
Infrastruct.
Interdepend.
Intrusion
management
Training
Bestpractice
Fault
Prevention
Fault
Removal
Fault
Tolerance
Fault
Forecasting
Pisa, 25-27/11/02, Workshops on &