G05 System Design II

MVC:

• The view subsystem sends updates to the controller subsystem and model subsystem

• The difference between 3 tier architectural style and MVC is that MVC is hierarchical

• Decouples data access and presentation, allowing multiple synchronized views of the same model

Concurrency:

• A race condition is a design flaw where the output of a process depends on the specific sequence of other events

• Logical concurrency is when threads are provided by hardware

• Addresses the non functional requirements flexibility and maintainability as tasks are assigned to separate threads

HW/SW Mapping:

• Addresses the question how UML models can be realised in code

• Control objects are mapped to processors, entity objects to memory and boundary objects to IO devices

• The difficulty of HW/SW mapping is determining the cost of the HW needed to realise the system

Access Control:

• During system design we model access rights by associating use cases with the actors

• Access right is the row in the access matrix and it models all possible actors that interact with the system

• Capability associates a (class, operations) pair with an actor

Software Control:

• Centralised design leads to additional communication overhead

• Centralised control can be modelled using the Fork diagram

• Event-driven centralised control is when control resides within the program code