architectural separation (mvc, arch model, seeheim). bakaev ilkhom professional network of...

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ARCHITECTURAL SEPARATION (MVC, ARCH MODEL, SEEHEIM).

Bakaev Ilkhom

PROfessional network of Master’s degrees in Informatics as a Second Competence – PROMIS (544319-TEMPUS-1-2013-1-FR-TEMPUS-JPCR)

Today’s Plan

1. Architecture separation 2. Design Patterns 3. Why MVC 4. What is MVC 5. What is ARCH model 6. What is SHEEHEIM model

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Architecture separation

The architecture of a computer system is a set of structures which include: components, the outside visible properties of these components and the relations between them.

The aim of architecture models is to supply a pattern for the design and the realization of the user interface.

They decompose the HMI (Human-Machine Interface) into modules and define appropriate roles for each module. These roles contribute towards the correct execution of the system.

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Architecture separation

Several architecture models have been put forward by researchers over the past twenty years. Three main types of architecture can be distinguished in the resulting research literature:

The Language Model (the precursor): presents an analogy between the human dialogue and the human-machine interaction.

Functional models: they bring the software and the interaction together into functional levels.

Agent-based Models: they organize an interactive system into a set of reactions and stimulus.

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Architecture separation

These architecture models recommend the same principle, based on the separation between the system (application) and the human-machine interface.

Therefore, the architecture has to separate application and interface, to define a distribution of the interface services, and to define an exchange protocol [18].

The advantage of separating the interface: it facilitates modifications which can be made to the interface without changing the application.

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The Language model

The Language model was proposed by [14]. This model decomposes the application and the human-machine interface in the same way as a language.

In spite of the fact that this model defines four levels of abstraction, it also has some drawbacks. Priority is given to the shape of the

information The level of abstraction of the protocols of

communication between components is not sufficiently clear [6].

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The Language model

The basic principles of the Language model have been used by many researchers, and have influenced the definition of several generic models. The most well-known are functional models.

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Functional models

The functional architecture models provide a separation between the application and the interface. The Seeheim model is the most widely known.

Seeheim Reference Architecture The Seeheim reference architecture

applies part -whole decomposition to the monolithic reference architecture.

Presentation

Dialogue

Application

Improved Seeheim

Uses compression to improve performance problems

Presentation

Dialogue

Application

Strengths of Seeheim Reference Architecture

A separate presentation function supports portability and modifiability.

A separate application layer allows modification of function without affecting the user interface.

A separate dialogue allows modifications to user interaction without rewriting the presentation.

Weaknesses of Seeheim Reference Architecture

Many modifications affect all three functions.

There are performance problems with sophisticated semantic feedback (which result in the need for compression).

Use of the architecture leads to separate notations for dialogue, presentation, and application layer; this is cumbersome.

Unit Operations and HCI Reference Architectures

Monolithicarchitecture

PAC/AMODEUS

MVC PAC

Seeheim Arch/Slinky

part-whole

part-whole

abstraction

is-a

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The Seeheim model

The Seeheim model (Cf. figure 1) was proposed in 1983 by Pfaff [27].

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The Seeheim model

This model works as follows: the presentation performs a lexical analysis in order to translate the statements of the user into computer language.

The dialogue controller provides a syntactic analysis of the interaction language. It also manages interaction between the presentation and the application.

The final module makes it possible to translate the statement into specification language in order to reach the application

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The Seeheim model

The Seeheim model has some drawbacks such as the separation between the dialogue controller component and the other components, which is not always true in reality.

Indeed, the application interface can use semantic information, which makes it possible to control feed-backs for example, to generate default values or to check errors

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The Arch model

The Arch model [1] is a revision of the Seeheim model. It defines a functional breakdown of the interface into five different elements (Cf. Figure 2).

Both the presentation component and the interaction component are a decomposition of the presentation of the Seeheim model. The interaction component manages the physical interactions with the user.

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The Arch model

The presentation component supplies a set of presentation objects which are independent of any toolkit.

The functional kernel carries out the domain concepts. The domain adapter is used for adjusting the differences in the modelling of conceptual objects between the functional kernel and the dialogue controller.

Note that the Arch model is limited in that it is centralized.

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The Arch model

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The Arch model

Seeheim and Arch provide canonical functional structures with big gain.

These models are useful as a structural framework for a design or a rough analysis of the functional decomposition of an interactive system.

Multi-agent reference models aim at a finer functional breakdown.

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Agent based model

Agent-based models are generally based on a modular decomposition of the elements of the interface (like functional models with levels of abstraction) as well as on a reorganization of the location of features and of data and the hierarchy between each entity.

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Agent based model

We shall not detail the notion of agent, but retain the following definition for the term agent:

"An agent acts according to a set of information received and perceived from its environment and according to the goal which it is pursuing".

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WHY MVC?

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Overview

1. Design Patterns 2. Why MVC 3. What is MVC

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PROBLEM

Problem - Without the separation of concerns a developer has to rely and wait for the feeds of others to complete his tasks. Productivity --

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SOLUTION

Solution - With separation of concerns by MVC, he can build applications faster, Unit test them easily without any involvement of other developers. Productivity ++

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MVC

Pattern? Architecture?

Framework?

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PATTERN

“ Each pattern is a three-part rule, which: expresses a relation between a certain

context (design context), a certain system of forces which occurs

repeatedly in that context (recurring design problem),

and a certain software configuration which allows these forces to resolve themselves (solution).“

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ARCHITECTURAL PATTERN:

Fundamental structural organization for software systems.

Architectural patterns are high-level strategies that concerns large-scale components, the global properties and mechanisms of a system.

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ARCHITECTURAL PATTERN:

“At the highest level, there are the architecture patterns that define the overall shape and structure of software applications.

Down a level is the architecture that is specifically related to the purpose of the software application.

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ARCHITECTURAL PATTERN:

Yet another level down resides the architecture of the modules and their interconnections. This is the domain of design patterns, packages, components, and classes.”

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FRAMEWORK:

A software framework is a universal, reusable software platform used to develop applications, products and solutions.

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MVC

In the MVC paradigm, the user input, the modeling of the external world, and the visual feedback to the user are explicitly separated and handled by three types of objects, each specialized for its task.

A software framework is a universal, reusable software platform used to develop applications, products and solutions.

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MVC

Model View  Controller

Model

ControllerView

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Model

The model is responsible for managing the data of the application.

It responds to the request from the view and it also responds to instructions from the controller to update itself

It is the lowest level of the pattern which is responsible for maintaining data.

The Model represents the application core (for instance a list of database records).

It is also called the domain layer

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View

The View displays the data (the database records).

A view requests information from the model, that it needs to generate an output representation.

It presents data in a particular format like JSP, ASP, PHP.

MVC is often seen in web applications, where the view is the HTML page.

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Controller

The Controller is the part of the application that handles user interaction.

Typically controllers read data from a view, control user input, and send input data to the model.

It handles the input, typically user actions and may invoke changes on the model and view.

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Working of MVC in web application

Questions39

Do controllers have a user interface? Does a view allow user input? Can a view send messages to the model? Can a view send messages to the controller? Can you have more than one view? Can you more than one model? Can you more than one controller? Is a controller just one file? A View?, A Model? Should the view UI be separate from the

controller interface?