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Patterns in Software Engineering Lecturer: Raman Ramsin^ Lecture 19^ Analysis Patterns

Part 2

Department of Computer Engineering

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Part^2 Sharif University of Technology

Patterns in Software Engineering – Lecture 19 Supporting PatternsSupporting

Patterns

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„^ The supporting patterns describe how to take analysis patternsand apply them:^ ^

Layered Architecture for Information Systems:

These patterns

consider the architecture for a client/server information system and howsuch a system can be layered to improve its maintainability.

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^ Patterns for Type Model Design Templates:

These patterns focus on

how conceptual models can be implemented, suggesting common

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patterns to turn analysis patterns into software. Association Patterns:

These patterns focus on examining modeling

techniques themselves and how advanced modeling constructs can beviewed as patterns. Department of Computer Engineering

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Sharif University of Technology

Patterns in Software Engineering – Lecture 19 Supporting Patterns:

Layered Architectures -

Three-Tier Architecture

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„^ Problem:

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^ The two-tier architecture couples the user interface too tightly to thedatabase design. ^ The database interface cannot support a rich model of the domain ^ The database interface cannot support a rich model of the domain. „ Solution:

Have three logical tiers: application, domain, and database. Department of Computer Engineering

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Sharif University of Technology

Patterns in Software Engineering – Lecture 19 Supporting Patterns:

Layered Architectures -

Tiered Architectures

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Two Tier

Three Tier

Department of Computer Engineering

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Sharif University of Technology

Patterns in Software Engineering – Lecture 19 Supporting Patterns:

Layered Architectures -

Presentation & Application Logic

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Department of Computer Engineering

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Sharif University of Technology

Patterns in Software Engineering – Lecture 19 Supporting Patterns:

Layered Architectures -

Database Interaction

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„^ Problem:

Working with a database. „^ Solution: „^ Solution:^ ^

Let the domain classes be responsible for saving themselves in thedatabasedatabase. Create a separate layer to handle the interactions between database anddomain objectsdomain objects. Department of Computer Engineering

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Sharif University of Technology

Patterns in Software Engineering – Lecture 19 Supporting Patterns:

Type Model Design Templates –

Implementing Generalizations

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„^ Problem:

Implementing generalization, especially if multiple „^ Problem:

Implementing

generalization, especially if multiple

and dynamic classification is involved. „ Solution:^ ^ Use inheritance.^ ^ Use classes for each combination of subtypes with multiple inheritance ^ Use classes for each combination of subtypes with multiple inheritance.^ ^ Use an internal flag.^ ^ Delegate to a hidden class (state pattern).^ ^ Copy and replace.Department of Computer Engineering

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Sharif University of Technology

Patterns in Software Engineering – Lecture 19 Supporting Patterns:

Type Model Design Templates

-^ Object Creation

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„^ Problem:

Creating an object. „^ Solution:

Use a creation method with arguments for all mandatory and immutable mappingsmandatory and immutable mappings.Department of Computer Engineering

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Sharif University of Technology

Patterns in Software Engineering – Lecture 19 Supporting Patterns:

Type Model Design Templates -

Entry Point

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„^ Problem:

Starting to look for objects „^ Problem:

Starting

to look for objects.

„^ Solution:^ ^

Let the class be responsible for storing and finding its instances Let^ the class be responsible for storing and finding its instances. Have a registrar find and store objects. Department of Computer Engineering

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Sharif University of Technology

Patterns in Software Engineering – Lecture 19 Supporting Patterns:

Type Model Design Templates –

Implementing Constraints

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„^ Problem:

Implementing constraints. „^ Solution:

Give each object an operation to check its constraint. Call it at the end of modifiers when debugging.Call it at the end of modifiers when debugging.Department of Computer Engineering

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Sharif University of Technology

Patterns in Software Engineering – Lecture 19 Supporting Patterns:

Association Patterns -

Associative Type

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Department of Computer Engineering

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Sharif University of Technology

Patterns in Software Engineering – Lecture 19 Supporting Patterns:

Association Patterns -

Keyed Mapping

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„^ Problem:

Representing values in a mapping that are keyed off another type. „ Solution:

Use a keyed mapping „^ Solution:

Use^ a keyed mapping. Department of Computer Engineering

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Sharif University of Technology

Patterns in Software Engineering – Lecture 19 Supporting Patterns:

Association Patterns -

Historic Mapping

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„^ Problem:

Recording previous values of a mapping. „^ Solution:

Use a historic mapping. Department of Computer Engineering

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Sharif University of Technology

Patterns in Software Engineering – Lecture 19 Supporting Patterns:

Association Patterns -

Historic Mapping

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Sharif University of Technology