SFWR ENG 3A04: Software Design II€¦ · MVC architecture is speciﬁcally used in applications where user interfaces are prone to data changes all the time MVC architecture typically

SFWR ENG 3A04:Software Design II

Dr. R. Khedri

OutlineSFWR ENG 3A04: Software Design II

Dr. Ridha Khedri

Department of Computing and Software, McMaster UniversityCanada L8S 4L7, Hamilton, Ontario

Term 1

Acknowledgments: Material based on Software Architecture Design by Tao et al. (Chapter 9)

Dr. R. Khedri SFWR ENG 3A04: Software Design II


Dr. R. Khedri

Outline

Part I: Review ofPrevious Lecture

Part II: Today’sLecture

Outline of Part I

1 Main/Subroutine Software Architecture

2 Master/Slaves Software Architecture

3 Layered Architecture

4 Virtual Machine



Dr. R. Khedri

Outline

Part I: Review ofPrevious Lecture

Part II: Today’sLecture

Outline of Part II

5 Overview

6 Model-View-ControllerMVC-IMVC-ll

7 Presentation-Abstraction-Control (PAC) Architecture



Dr. R. Khedri

Main/SubroutineSoftwareArchitecture

Master/SlavesSoftwareArchitecture

LayeredArchitecture

Virtual Machine

Part I

Review of Previous Lecture



Dr. R. Khedri

Overview

Model-View-Controller

Presentation-Abstraction-Control (PAC)Architecture

Part II

Today’s Lecture



Dr. R. Khedri

Overview



Interaction Oriented Software ArchitectureOverview

More and more software applications that involve userinput and output interactions

We focus on the software architecture that bestsupports user interaction

Interaction oriented software architecture decomposesthe system into three major partitions

Data module (provides the data abstraction& corebusiness logic)Flow control module (determines the flow controls,view selections, communications between modules, jobdispatching, and certain data initializations andconfigurations)View presentation module (responsible for visual oraudio data output presentation)



Dr. R. Khedri

Overview




This architecture allows the separation of userinteractions from data abstraction and business dataprocessing

Allows multiple views for a same data set

Even for a specific view presentation, the interfaces mayneed to change very often (the loose coupling betweendata abstractions and its presentations is very helpful)

A control module plays a central role that mediates thedata module and view presentation modules

All three modules may be completely connected



Dr. R. Khedri

Overview




There are two categories of interaction orientedarchitecture:

Presentation-Abstraction-Control (PAC)

Model-View-Controller (MVC).

They are different in their flow controls and structureorganization

The MVC does not have a clear hierarchical structureand all three modules are connected together



Dr. R. Khedri

Overview




The PAC is an agent based hierarchical architecture

The system is decomposed into many cooperatingagentsEach agent has three components (Presentation,Abstraction, and Control)The Control component in each agent is in charge ofcommunications with other agentsThe top-level agent provides core data and businesslogicsThe bottom level agents provide detailed specific dataand presentationsA middle level agent may play a role of coordinator oflow-level agentsThere are no direct connections between Abstractioncomponent and Presentation component in each agent



Dr. R. Khedri

Overview


MVC-I

MVC-ll


Interaction Oriented Software ArchitectureModel-View-Controller

Most of Web developers are familiar with MVCarchitecture

Widely adopted for Web server site interactiveapplication design such as online shopping, onlinesurvey, online student registration, etc.

MVC architecture is specifically used in applicationswhere user interfaces are prone to data changes all thetime

MVC architecture typically supports ”look and feel”features in GUI application

The Java Swing components and Java Swing layoutmanagers are designed in MVC architecture



Dr. R. Khedri

Overview


MVC-I

MVC-ll



Summary:The Controller

manages the user input requestscontrols the sequence of user interactionsselects desired views for output displaysmanages all initialization, instantiations, andregistrations of other modules in the MVC system

The Model moduleprovides all core functional services and encapsulates alldata detailsdoes NOT depend on other modules, and it does notknow which views are registered with or attached to it

The View moduleis responsible for displaying the data provided by theModel module and updating the interfaces wheneverthe data changes



Dr. R. Khedri

Overview


MVC-I

MVC-ll


Interaction Oriented Software ArchitectureModel-View-Controller (MVC-I)

The MVC-I is a simple version of MVC architecture

The system is simply decomposed into twosub-systems:

Controller/View

It handles input and output processing and theirinterfaces

It registers with (attaches to) data module

ModelIt copes with all core functionality and data

It notifies the Controller-View module of any datachanges in the Model module



Dr. R. Khedri

Overview


MVC-I

MVC-ll



The connection between the Controller/View and theModel can be designed in a pattern of subscribe/notify

The Controller/View subscribes the Model and theModel notifies the Controller/View of any changes

The Controller/View is an observer to the data in theModel of MVC

Read the example given in Chaptre 9, Section 9.2.1 tosee how MVC-I architecture concretely works



Dr. R. Khedri

Overview


MVC-I

MVC-ll



Figure: MVC-I architecture



Dr. R. Khedri

Overview


MVC-I

MVC-ll


Interaction Oriented Software ArchitectureModel-View-Controller (MVC-II)

MVC-II architecture

The Model module provides all core functionality anddata supported by database (Same as MVC-I)

The View module displays the data from the Modelmodule

The Controller module

It takes input requests, validates input data, initiatesthe Model and the View and their connection

It dispatches tasks



Dr. R. Khedri

Overview


MVC-I

MVC-ll


Interaction Oriented Software ArchitectureModel-View-Controller (MVC-II)

The Controller and the View register with the Modelmodule

Whenever the data in the Model module is changed theView module and the Controller module are notified

Comparison to MVCI

In both MVC-I and MVC-II, Model module plays anactive role

In MVC-Il architecture, the View module and theController module are completely separated



Dr. R. Khedri

Overview


MVC-I

MVC-ll



Figure: MVC-II architecture



Dr. R. Khedri

Overview


MVC-I

MVC-ll



Figure: A detailed MVC-II architecture



Dr. R. Khedri

Overview


MVC-I

MVC-ll



Figure: Sequence diagram for MVC architecture



Dr. R. Khedri

Overview


MVC-I

MVC-ll



Figure: MVC architecture on Java Web platform



Dr. R. Khedri

Overview


MVC-I

MVC-ll



Applicable domain of MVC architectureSuitable for interactive applications (multiple views areneeded + volatile graphics interfaces)

There are clear divisions between controller, view, anddata modules (different professionals can be assignedto work on different aspects of the system)

BenefitsMany MVC vendor frameworks available

Multiple views synchronized with same data model

Easy to plug in new or change interface views, updateinterface views with new technologies

Very effective for developments (team = graphics,programming, and data base professionals)



Dr. R. Khedri

Overview


MVC-I

MVC-ll



Limitations

Does not fit agent-oriented application such asinteractive mobile, robotics applications

Multiple pairs of controllers and views based on thesame data model make any data model changeexpensive

The division between the View and the Controller isnot very clear in some cases

Related architecture

Implicit invocation architecture such as event-based,Multi-tierarchitecture, andPresentation-Abstraction-Control (PAC)



Dr. R. Khedri

Overview



Interaction Oriented Software ArchitecturePresentation-Abstraction-Control (PAC)Architecture

The PAC architecture is quite similar to MVC

The PAC was developed from MVC to support theapplication requirement of multiple agents in additionto the interactive application requirement

The PAC three components concepts are applied to allconcrete sub-system architecture

It is very suitable for any distributed system where eachremote agent has its own functionalities with data andinteractive interface

Another feature: all agents need to communicate withother agents in a well structured way



Dr. R. Khedri

Overview




Figure: A single agent in PAC



Dr. R. Khedri

Overview




Applicable domain of PAC architectureInteractive system where the system can be dividedinto many cooperating agents in a hierarchicalstructure (Each agent has its specific job)

The coupling among the agents is expected very loose(change of one agent will not affect the others)

BenefitsSupporting multi-tasking, multi-viewing

Supporting agent reusability and extensibility

Easy to plug in new agent or replace an existing agent

Supporting concurrency (agents are in different threadsor different devices or computers)



Dr. R. Khedri

Overview




LimitationsOverhead due to

the control bridge between presentation andabstractionthe communications of controls of many agents

Difficult to determine the right numbers of the agentsbased on the loose couplings between agents and highindependence of each other

Development complexity: due to complete separation ofpresentation and abstraction (communications betweenagents only take place between the controls of agents)

Increased complexity of the system design andimplementation

Related ArchitectureLayered architecture, multi-tier architecture, MVCarchitecture



Dr. R. Khedri

Overview




Documents

SFWR ENG 3A04: Software Design II€¦ · MVC architecture is speciﬁcally used in applications where user interfaces are prone to data changes all the time MVC architecture typically