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Hierarchical Architecture (Main/Subroutine Architecture (Function Call…
Hierarchical Architecture
General Rules
Upper layers provide more abstract functionality in the form
of user interfaces such as
Services at lower level provides more specific functionality
down to fundamental utility services such as
Middle layers provide more domain dependent functions such
as
Any changes to a specific layer may affect only its adjacent
upper layers.
Master-Slave
The slaves provide replicated services to the master
A variant of main-subroutine architecture
It supports Fault tolerance and system reliability
The master selects a particular result among slaves by
certain selection strategies.
Main/Subroutine Architecture
Design
Usually Requirement Spec. Specified in Data Flow Diagram
Objective: Map from DFD to Main/Subroutine Design
The oldest and most widely used architecture.
Encourage re-use of modules
Idea
System decomposed into sub-routines
A “main” program calls sub-routines and accomplishes task
Benefits
Easy to decompose the system
Can still be used in sub-system of OO Design.
Limitations
Globally shared data are vulnerable
Tight coupling may cause ripple impacts as compared to OO
design
Function Call Supported by Assembly
Call the subroutine
Software Interrupt
Jump, Long Jump, Call instruction
Protect old register values by pushing to stack
Set parameters in register
Function Call Supported by High Level Language
Parameter passing
Pass by reference
Pass by value
Much more convenient
Much more tricky
Layered
Limitations
Exception and error handling
Lower runtime performance
Many applications can not fit this architecture
For systems that can be divided between portions providing
generic services to the application of the system
For applications which have classes that are close related
each other
Benefits
Promotion of portability
Enhanced reusability and interchangeability
Incremental software development
Enhanced independence of upper layer to lower layer
Component-based technology is a suitable