1. CSCI 578 Software Architectures
Exam #2 Review

2. Materials you are responsible for
Chapters 9-17 in the text book
Also Chapter 8 on Architectural Analysis since we didn’t cover this in the first exam
All lecture material from Implementation Architectures through People, Roles and Teams (Week 15)
Course Project
C2SADEL material/addendum

3. Exam Closed book, closed note Format Write in answers
No multiple choice

4. Material Review Implementing Architectures
Mapping problem of design decisions to implementation artifacts (code, executables, etc.)
Common Element Mapping
Understand how components, connectors, interfaces, configurations are reified in the actual system implementation
One way versus Round-trip Mapping
Architectural Implementation Frameworks
a piece of software that acts as a bridge between a particular architectural style and a set of implementation technologies

5. Material Review Architectural implementation framework examples
stdio, java.io, iostream => pipe and filter
Evaluating architectural implementation frameworks
Platform support, fidelity, matching assumptions, efficiency, size, cost, ease of use, reliability, robustness, availability of source code, portability, long-term maintainability and support
Middleware
Represents the implementation-level reification of software connectors
New Frameworks
Avoid constructing these unless you have to!

6. Material Review Applied Architectures
8 limitations (“fallacies”) of distributed computing (Deutsch & Gosling)
The network is reliable
Latency is zero
Bandwidth is infinite
The network is secure
Topology doesn’t change
There is one administrator
Transport cost is zero
The network is homogeneous

7. Material Review Applied Architectures REST/WWW Akami
Architectural principles
Resources, resources include metadata + bits, context free communication (stateless), small set of well defined methods, representation metadata for caching, presence of intermediaries to distributed computation/workload
Akami
Caching of content and localized delivery architecture
Google MapReduce/GFS
Distribution of computation/parallelization and data over a commodity cluster of machines

8. Material Review Applied Architectures Overall takeaways
Grid Protocol Architecture (Globus)
P2P Architectures
Napster, Gnutella
Skype
Bittorrent
Overall takeaways
A great architecture is the ticket to runaway success
A great architecture reflects deep understanding of the problem domain
A great architecture probably combines aspects of several simpler architectures
Develop a new architectural style with great care and caution. Most likely you don’t need a new style.

9. Material Review Designing for Non-Functional Properties (NFPs)
A software system’s non-functional property (NFP) is a constraint on the manner in which the system implements and delivers its functionality
Example NFPs
Efficiency
Complexity
Scalability
Heterogeneity
Adaptability
Dependability

10. Material Review
Ascertain the role of software architecture in ensuring various NFPs
At the level of major architectural building blocks
Components
Connectors
Configurations
As embodied in architectural style-level design guidelines
Efficiency, Complexity, Scalability, Heterogeneity, Adaptability, Dependability

11. Material Review Security and Trust Design Principles
“The protection afforded to an automated information system in order to attain the applicable objectives of preserving the integrity, availability and confidentiality of information system resources (includes hardware, software, firmware, information/data, and telecommunications).”
National Institute of Standards and Technology
Design Principles
Least Privilege: give each component only the privileges it requires
Fail-safe Defaults: deny access if explicit permission is absent
Economy of Mechanism: adopt simple security mechanisms
Complete Mediation: ensure every access is permitted
Design: do not rely on secrecy for security

12. Material Review Security and Trust Design Principles
Separation of Privilege: introduce multiple parties to avoid exploitation of privileges
Least Common Mechanism: limit critical resource sharing to only a few mechanisms
Psychological Acceptability: make security mechanisms usable
Defense in Depth: have multiple layers of countermeasures

13. Material Review Decentralized
No centralized authority to coordinate and control entities
Independent peers, with possibly conflicting goals, interact with each other and make local autonomous decisions
Presence of malicious peers in open decentralized applications
Need for measures to protect peers against malicious attacks

14. Material Review Some Threats of Decentralization
Impersonation: Mallory says she is Bob to Alice
Fraudulent Actions: Mallory doesn’t complete transactions
Misrepresenting Trust: Mallory tells everyone Bob is evil
Collusion: Mallory and Eve tell everyone Bob is evil
Addition of Unknowns: Alice has never met Bob

15. Decentralized Auctioning
Carol
Bob
Alice
Mallory
(malicious)
Decentralized
Auctioning
Open decentralized application
Independent buyers/sellers
Potentially malicious participants
Need to counter threats
Marvin
(malicious)

16. Impersonation Bob Alice Bob is reliable and everyone
has a good opinion about Bob
“I am Bob”
Mallory
(malicious)

17. Fraudulent Actions Alice pays for the items Marvin does
not ship the items
Marvin “seller”
(malicious)
Alice “buyer”

18. Misrepresentation Bob Alice Bob is reliable and everyone
has a good opinion about Bob
“Bob is unreliable”
Mallory
(malicious)

19. Collusion Bob Alice Bob is reliable and everyone
has a good opinion about Bob
“Bob is unreliable”
Marvin
(malicious)
Mallory
(malicious)

20. Addition of Unknowns Carol (new entrant in the system)
Carol is new and does not
know Alice; she is not sure
whether to interact with Alice
Bob has no information
about Carol; he is not sure
whether to interact with Carol
Alice
Bob

21. Communication Manager Application Trust Rules
Material Review
PACE Architecture
Communication
Layer
Information
Trust
Communication Manager
External
Internal
Key
Manager
Signature Manager
Application Trust Rules
HTTP Sender
Custom Protocols
Multicast Manager
Multicast Handler
Credential
A P P L I C A T I O N

22. Material Review Deployment and Mobility
Deployment is the process of placement of a system’s software components on its hardware hosts
Changing the deployment of a component during runtime is called migration or redeployment
Migration or redeployment is a type of software system mobility
Mobility entails a superset of deployment issues

23. Material Review 4 Major Deployment Activities Planning Modeling
Analysis
Implementation

24. Material Review Deployment Implementation Release Install Activate
Deactivate
Update
Adapt
Reconfigure
De-install or remove
De-release or retire

25. Material Review Code Mobility Paradigms Remote evaluation
Re-deploy needed component at runtime from a source host to a destination host
Install component on the destination host
Code-on-demand
Same as remote evaluation, but roles of target and destination hosts are reversed
Mobile agent
Migration of a stateful software component that needs some remote resources to complete its task

26. Material Review People, Roles and Teams Architect desired skills
Software development expertise
Domain expertise
Communicator
Strategist
Consultant
Leader
Technologist
Cost estimator
Cheerleader
Politician
Salesperson

27. Material Review Pitfalls of the architecture team Imbalance of skills
Lack of software development experience
Lack of domain expertise
Lack of authority
Team acts as committee
Life in ivory tower
Confusing tools/techniques/methodologies with architectures
Procrastination