Architectures

• Component: modular unit with an interface
• Connector: mediates communication between components
• Software architecture: organization of components
• System architecture: instantiation of software architecture on real machines
• Autonomic system: adapts to environment by monitoring behaviour and adapting

Styles:

• Layered
  • communicating between layers takes one round trip (two message delays to send and receive)
• Object-based
  • e.g. Java remote method invocation (RMI)
• data-centred
• event-based
  • e.g. pub sub

Multi-tiered architectures

Logical layers need to be mapped onto physical tiers. In a two tiered system (client/server), you can decide which parts to put on which tier.

Horizontal vs Vertical distribution

• Vertical: logical layers of a system are separate physical tiers. (e.g. separate machines for application server, database)
• Horizontal: one logical layer is split across multiple machines (e.g. hash partitioned data sets, known as sharding)