Arch-1 9.Architecture

Arch-2 What’s Architecture? Description of sub-system –Components/sub-systems –Their interaction Framework for communication

Arch-3 Architectural Design Establishes a basic structural framework Identifies major components of a system Communication between them

Arch-4 Why do you need it? Useful for communication Helps analyze ability to meet requirements Leads to repeatable, reusable concepts

Arch-5 Issues to deal with Potentially conflicting issues Performance –Need to keep inter sub-system communication minimum –Level of granularity of components Security –Each layer has to deal with security –Well protected information in inner layers Safety/validation –Need to isolate into one or a few sub-systems Availability/reliability/redundancies –What about availability, load, failure, fault tolerance Maintainability –Smaller sub-system to make it easier to maintain

Arch-6 Architectural Representation Block diagrams generally used Effective to communicate different sub- systems Not effective to describe sub-system interface Goal: design so that requirement change does not propagate across several sub- systems

Arch-7 Developing Architectural Design Very creative process Job of a system architect Varies based on system, experience, requirements

Arch-8 General Questions Questions and considerations Do we have a template to start with? Style System structure Sub-system decomposition Measure of quality Documentation

Arch-9 Models Client-server model Layered model Combined style Static Structure Model Dynamic Process Model –Processes at runtime Interface Model –Sub-system interface Relationship Model –Dataflow, communication, … Distribution Model –Distribution across processors, computers

Arch-10 Organization Decided by Data Services Functional

Arch-11 Repository Considerations –Efficiency –Format of data –Data Usage –Change to format –Centralization and maintenance –Force on the sub-systems Central StorageMessage Passing

Arch-12 May be on one box May be across machines May be physical distribution or simply logical Client-Server Model ClientServer Different services: File, Printing, Computation, …

Arch-13 Layering How do we structure the application in a way that it is maintainable, robust, reliable, secure and robust? Separate the components into layers The layers will have loose coupling Each layer is cohesive Components in a layer interact with –Components within the layer –Components in layer below it

Arch-14 Layering … In a strict layering, components do not talk to any layer other than the one below it In a more relaxed layering, components may bypass one or two layers below Layer n Layer 3 Layer 2 Layer 1

Arch-15 Tier Distribution Layering is more logical Tier distribution talks about how the application is distributed across different hardware The physical tiers is composed of different computers that share: –Resources Like sockets, disc space, etc. –Operational requirements Security, scalability, –Constraints Location may be dictated by constraints like security

Arch-16 Three-Tier Distribution Client Tier Application Tier (Business Tier) Data Tier ASP.NET/ Win Forms/ Web Services Component Libraries ADO.NET/Database Access