Friday, August 18, 2006

On SOA

What is SOA
Architectural Style
Business Alignment
Reduced assumptions (loose coupling)
Builds on ideas from component software, distributed objects, and MOM
Message based communication
A service is a program you interact with via message exchanges
-Services are built to last
-Encompass a business perspective
-Stability and robustness are critical
A system is a set of deployed services cooperating in a given task
-Systems are built to change
-Adapt to new services after deployment

On Architecture

What’s Architecture

“the fundamental organization of a system, embodied in its components, their relationships to each other and the environment, and the principles governing its design and evolution”. (IEEE 1471)

Architecture defines major components ,
Architecture defines component relationships (structures) and interactions,
Architecture defines the rationale behind the components and the structure
Architecture is not a single structure -- no single structure is the architecture
Architecture represents the set of earliest design decisions
-Hardest to change
-Most critical to get right
Architecture is the first design artifact where a system’s quality attributes are addressed

Architecture serves as the blueprint for the system but also the project:
-Team structure
-Documentation organization
-Work breakdown structure
-Scheduling, planning, budgeting
-Unit testing, integration
Architecture establishes the communication and coordination mechanisms among components


Architecture is important
-it should be analyzed
Architecture can be prescribed
-decisions should be analyzed
Architecture is central for communicating
-it should be documented
Architecture is expensive to change
-it is cheaper to analyze early
Architecture affects the entire project
-many stakeholders should be involved
Requirements can be understood early
-architecture should be designed to meet them

Different view points

End user view:
Performance
Availability
Usability
Security

Developer’s view:
Maintainability
Portability
Reusability
Testability

Business user view
Time To Market
Cost and Benefits
Projected life time
Targeted Market
Integration with Legacy System
Roll back Schedule

Tuesday, August 15, 2006

DSL Links

Good PPTs on DSL
http://www.microsoft.com/uk/msdn/architecture/solution/default.mspx

Saturday, August 05, 2006

The Eight Fallacies of Distributed Computing

The Eight Fallacies of
Distributed Computing
Peter Deutsch
Essentially everyone, when they first build a distributed application, makes the following eight assumptions. All prove to be false in the long run and all cause big trouble and painful learning experiences.
1. The network is reliable
2. Latency is zero
3. Bandwidth is infinite
4. The network is secure
5. Topology doesn't change
6. There is one administrator
7. Transport cost is zero
8. The network is homogeneous

Tuesday, August 01, 2006

Stats : MSN Spaces

The service sports 123 million unique users, with roughly 3 million users visiting MSN Spaces every second. Users upload six million photos to the service every day, requiring 1TB of additional storage every nine days. To put these numbers in perspective, it took MSN Messenger six years to reach 160 million users: MSN Spaces will reach 130 million users in only 18 months