ARCHITECTURAL STYLES - 2

An architectural style defines a family of Systems in terms of a pattern of structural Organization. It determines:

– The vocabulary of components and connectors– A set of constraints on how they can be combined.

Dr Reeja S RProfessorCSE DeptSJEC Vamanjoor, Mangalore

ARCHITECTURAL STYLES - 2

Layered systemsRepositoriesinterpreters

Layered Systems

Layered Systems

Components – layers Connectors – procedure calls

Each layer acts as a Server: service provider to layer “above” Client: service consumer of the layer “below”

Examples

Networking protocolsOperating System

Layered pattern - variant

Closed architecture Open architecture

Advantages

Support design based on increasing levels of

abstraction – thereby partitioning a complex problem into a sequence of incremental steps

Supports enhancement since changes to one layer affects at the most 2 adjacent layer

Supports reuse - since different implementations (with identical interfaces) of the same layer can be used interchangeably

Disadvantages

All systems cannot be structured in a layered fashion

It is quite difficult to get the right level of

abstraction.

The system may suffer lower performance

REPOSITORIES

Repositories

Repositories Architectural Style

Components A central data structure representing the current

state of the system. A collection of independent components that operate

on the central data structure.

Connectors Procedure calls or direct memory accesses.

Variants

1. Type of transactions in an input stream trigger selection of process to execute

2. Current state of the central data structure is the main trigger for selecting processes to execute.

Ex: Blackboard

BlackboardTypically used for AI systems and in applications requiring

complex interpretations of signal processing, such as speech and pattern recognition.

Distance

Object Location

…

Visual Process

or

Motion Syste

m

Voice Synthesi

zer

Blackboard

Object Location

…

o1 L1o2 L2

Distance

Object Location

…

o1 L1o2 L2

10

Visual Process

or

Motion Syste

m

Voice Synthesi

zer

Blackboard

If(dist >=3)

Distance

Object Location

…

o1 L1o2 L2

8

Visual Process

or

Motion Syste

m

Voice Synthesi

zer

Blackboard

If(dist >=3)

Distance

Object Location

…

o1 L1o2 L2

6

Visual Process

or

Motion Syste

m

Voice Synthesi

zer

Blackboard

If(dist >=3)

Distance

Object Location

…

o1 L1o2 L2

4

Visual Process

or

Motion Syste

m

Voice Synthesi

zer

Blackboard

If(dist >=3)

Distance

Object Location

…

o1 L1o2 L2

2

Visual Process

or

Motion Syste

m

Voice Synthesi

zer

Blackboard

If(dist < 3)

Repositories Advantages

Efficient way to store large amounts of data. Centralized management for backup, security and

concurrency control

Disadvantages Must agree on a data model a priori. Data evolution is expensive

INTERPRETERSSuitable for applications in which the most appropriate language or machine for executing the solution is not directly available

Interpreter

An interpreter takes a program written in one language and interprets it to another language

Interpreter

Interpreter

An interpreter has 4 Components: “Program” being executed and its data Interpretation engine and its state

Connectors procedure calls and shared state.

Interpreter Examples

Programming Language Compilers: Java, Smalltalk

Rule Based Systems: Prolog, Coral Scripting Languages: Awk, Perl