Software Engineering General architecture

Architectural components:  Program organisation overview Major building blocks in a system Definition of each building block’s area of responsibility  A building block should know as little as possible about other building blocks’ areas of responsibility  Communication rules for each building block should be well defined

General architecture  Major classes Responsibilities of each major class Interaction with other classes Class hierarchies State transitions Object persistence Organisation of classes in subsystems

General architecture  Data design Major files and table designs to be used Access policies (sequential, direct, etc.) Storage policies High-level organisation and contents of data and databases Typically, data should be accessed directly by only one class or subsystem

General architecture  Business rules Using the terminology of General Systems Theory, environmental rules that affect the behaviour of the system

General architecture  User interface design Interface paradigm(s) Architecture should be such that interface could be replaced without affecting other parts of the system

General architecture  Resource management Database connections Threads Handles Memory

General architecture  Security Manipulation of buffers Rules for handling untrusted data Encryption Level of detail contained in error messages Protection of data in memory

General architecture  Performance issues Performance goals Performance bottlenecks  Scalability  Interoperability

General architecture  Internationalisation / localisation Obs: issue of growing importance nowadays  Input / Output I/O policy (look ahead, look behind, just in time) I/O error detection level (field, record, stream, file, etc.)

General architecture  Error processing Corrective versus detective Active versus passive Error propagation policy Conventions for handling error messages Exception handling policy  At what levels are errors handled?  What is the level of responsibility of each class for validating input data? Tailor made error processing or use development environment pre-fabricated solutions?

General architecture  Fault tolerance Expected fault tolerance Fault tolerance strategies  Architectural feasibility Is proposed design viable, considering available resources and proposed requirements?  Overengineering How to ensure system level robustness?

General architecture  “Buy” or build?  Reuse decisions  Architecture recurring revision strategy

General architecture  General architecture quality How to preserve conceptual integrity Clearly stated architecture’s objectives Motivations for all major decisions Machine- and language-independent architecture Multiple views NO COMPROMISING!