Tài liệu Module 12: Summary docx

Summarize the logical design considerations for each of the layers of the Enterprise template and in particular the use of design patterns.. Design Patterns and Design Tools in Logical D

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Instructor Notes

This module provides students with a summary of the important logical and

physical design considerations for each of the layers in the Enterprise template

After completing this module, students will be able to:

! Summarize the logical design considerations for each of the layers of the Enterprise template and in particular the use of design patterns

! Summarize the physical design considerations for each of the layers of the Enterprise template and in particular the use of technology

! Review the key technologies that impact multiple layers

! Summarize the best practices for each of the layers of the Enterprise template

! Discuss future enhancements for Market Purchasing

Materials and Preparation

This section provides the materials and preparation tasks that you need to teach this module

Required Materials

To teach this module, you need the following materials:

! Microsoft® PowerPoint® file 1910A_12.ppt

! Module 12: Summary

Preparation Tasks

To prepare for this module, you should:

! Read all of the materials for this module

Presentation:

60 Minutes

Lab:

00 Minutes

Module Strategy

Use the following strategy to present this module:

! Design Patterns and Design Tools in Logical Design The purpose of this section is to summarize the use of design patterns in the logical design of the various layers of the architecture template The review

is done by design pattern category

In the topic “Creational,” note that there are no design patterns that are useful

In the topic “Structural,” note that there are three design patterns—Facade, Composite, and Adapter—that are useful

In the topic “Behavioral,” note that there are three design patterns—

Observer, Iterator, and State—that are useful

In the topic “Other Patterns,” note that there are two design patterns—Authenticate and Queue—that are useful Also note that there are two modeling techniques that are useful: metaphor and entity relationship diagram (ERD)

! Technology Usage in Physical Design The purpose of this section is to summarize the use of technology in the three main functions of an application: external interactions, business logic, and state management For each technology, a summary of its advantages and disadvantages is presented In addition, this section reviews two technologies that are common to the physical design of all components: security and error handling

In the topic “External Interactions,” note that there are six technologies reviewed: thin client, rich client, Message Queuing, Extensible Markup Language (XML), distributed Component Object Model (DCOM), and Simple Object Access Protocol (SOAP)

In the topic “Business Logic,” note that there is only one technology under consideration: COM+

In the topic “Data Store,” note that there are only two technologies under consideration: Microsoft SQL Server™ and Active Directory™

! Best Practices The purpose of this section is to summarize the best practices for the logical and physical designs of an application according to the various layers of the Enterprise template

! Design Validation The purpose of this section is to summarize the validation mechanisms for logical and physical designs

! Future Enhancements to Market Purchasing The purpose of this section is to emphasize that a good design must be easily extensible and that the concept of extensibility can be tested by the introduction of future enhancements to an application

# Overview

! Design Patterns and Design Tools in Logical Design

! Technology Usage in Physical Design

! Best Practices

! Design Validation

! Future Enhancements to Market Purchasing

This module presents a summary of the Enterprise template and highlights the important logical and physical design considerations for each of the layers in the Enterprise template

After completing this module, you will be able to:

! Summarize the logical design considerations for each one of the layers of the Enterprise template and in particular the use of design patterns

! Summarize the physical design considerations for each one of the layers of the Enterprise template and in particular the use of technology

! Review the key technologies that affect multiple layers

! Summarize the best practices for each of the layers of the Enterprise template

! Discuss future enhancements for Market Purchasing

In this module, you will

review a summary of the

material presented in this

course

# Design Patterns and Design Tools in Logical Design

In this section, you will

review the use of design

patterns in the logical design

of an application

Creational

Design Pattern Layer

None System Services

None Data Services

None Data Access Layer

None Business Logic

None Facade

None User Services

The creational design patterns that are proposed by the book Design Patterns by

Erich Gamma, Richard Helm, Ralph Johnson, and John Vlissides, which include Abstract Factory, Builder, Factory Method, Prototype, and Singleton, were reviewed for their application to the various Enterprise template layers The conclusion drawn was that none of these design patterns are necessary because the functionality that the design patterns provide is available through either the operating system or component services

The only design pattern that posed an issue is the Singleton A Singleton ensures that a class has only one instance and provides a global point of access

In this topic, you will see a

summary of the use of

creational design patterns in

the logical designs of

various architecture

template layers

Structural

Design Pattern Layer

None System Services

None Data Services

Composite Adapter Data Access Layer

Composite Business Logic

Facade Facade

None User Services

There are eight structural design patterns in the Design Patterns book: Adapter,

Bridge, Composite, Decorator, Facade, Flyweight, and Proxy Three have proven to be useful in the logical design: Adapter, Composite, and Facade Unsurprisingly, the Facade pattern is the cornerstone for the Facade layer As discussed in detail in Module 5, “The Facade Layer,” the Facade pattern provides for a common secure interface to the internals of an application This interface allows user services to become impervious to changes in the internal structure of applications

The Composite structural pattern is useful when an object such as a requisition can contain several objects, such as line item details Composite patterns are useful in the business logic layer and in the data access layer (DAL)

Finally, the Adapter structural design pattern is useful in the logical design of DAL objects that need to create uniform access to different types of data Each DAL component translates the underlying data store into a format suitable for use in the rest of the system

In this topic, you will see a

summary of the use of

structural design patterns in

the logical designs of

various architecture

template layers

Behavioral

Design Pattern Layer

None System Services

None Data Services

Iterator Data Access Layer

Observer Iterator State

Business Logic

None Facade

None User Services

There are eleven behavioral design patterns in the Design Patterns book: Chain

of Responsibility, Command, Interpreter, Iterator, Mediator, Memento, Observer, State, Strategy, Template Method, and Visitor Three have proven to

be useful in the logical design: Iterator, Observer, and State

The Iterator behavioral design pattern is useful when there is a need to browse through a collection of objects In general, following the lead of Sten and Per

Sundblad in Scalable Visual Basic and MTS Applications, it is useful to modify the definitions of the patterns from the Design Patterns book and combine the

functionality of the List class with that of the ListIterator class The Iterator

design pattern is useful in the business logic layer and in the DAL

The Observer behavioral pattern that manages the changes of state is very useful in the logical design of the business logic layer For example, it can be used where there are many instances when there is a one-to-many dependency between objects such that when one object changes its state, all its dependents are notified or updated automatically

Finally, the State behavioral design pattern that also manages the changes of state is very useful in the logical design of the business logic layer, where there are many instances when the object behavior must change when its state changes

In this topic, you will see a

summary of the use of

behavioral design patterns

in the logical designs of

various architecture

template layers

Other Patterns

Design Pattern Layer

Authenticate System Services

ERD Data Services

None Data Access Layer

Queue Business Logic

None Facade

Metaphor User Services

In this course, the work from the Design Patterns book was extended to include

two new behavioral design patterns: Queue, and Authenticate

The Queue behavioral design pattern describes a frequent occurrence in enterprise applications: a many-to-many relationship between objects that cannot interact directly because of both spatial and temporal limitations This phenomenon typically occurs in the logical design of business logic that uses logic from one application in a second application

The Authentication design pattern is usually implemented in the system services, and it defines a many-to-one relationship between objects, so that one

or more objects can request authentication from a single object that will maintain a user database

The user services can use many of the behavioral design patterns However, the most important part of user services is identifying a metaphor The metaphor is the underlying model for representing the interaction between a user and the information system that is supporting the user in the particular system

The data services do not have any design patterns useful for logical design The most appropriate tool to use is entity relationship diagrams (ERD)

In this topic, you will see a

summary of the use of new

behavioral design patterns

in the logical designs of

various architecture

template layers

# Technology Usage in Physical Design

The external interactions are the part of an application that permits collaboration with users and other applications

The business logic is the part of the application that is intelligent; it is capable

of making decisions based on pre-defined rules

Finally, state management is the mechanism that serves as an application’s memory This memory could be short-term or long-term, depending on the design

This review looks at the technology according to these criteria rather than according to the Enterprise template layers, since the Enterprise template layers

is only one approach for logical design of an application, while technology application to physical design can be used for any logical design

For each category, the relevant technologies will be presented A brief summary

of the advantages and disadvantages for each technology’s adoption in the physical design will also be presented

In addition, this section includes a review of two technologies that are used in all layers of the Enterprise template: security and error handling These technologies apply to the physical designs of all components in an enterprise application

In this section, you will

review the important

technology considerations in

the physical design of

enterprise applications

External Interactions

Standards are still emerging

$Can be used in all layers of the Enterprise template XML

Compensating transactions

$Available on many platforms Message Queuing

Unproven

$Universality SOAP

Configuration management

$Scalability DCOM

Platform specific

$High use of resources Rich client

Poor use of client and network resources

$Any platform, any browser Thin client

Disadvantage Advantage

Technology

At present, there are six technologies that can be used to facilitate the cooperation between an application and its users and an application and its counterpart applications

In the realm of interacting with outside applications and users, there are currently two groups of technologies, which have been labeled thin client and rich client You would choose a thin client for universality and a rich client for performance

In the area of component interoperability, four technologies are proposed, three

of which are in current use (Message Queuing, XML, and DCOM) and one that looks very promising: Simple Object Access Protocol (SOAP)

Of those in current use, both Message Queuing and Distributed Component Object Model (DCOM) are well understood, but there are administration issues

to consider The administration tasks include setting up queues, defining queue attributes, and configuring the components to use other components running on other nodes New Microsoft® back-end servers such as AppCenter server might reduce the administrative burden

Extensible Markup Language (XML), while relatively new, holds excellent promise as a medium for the exchange of data A new Microsoft server, Microsoft BizTalk™, might facilitate the adoption of XML as a data exchange standard

While SOAP has been covered in detail, it was not used in the Market Purchasing application It is still an unproven technology

In this topic, you will see a

summary of the use of

external interaction

technologies in the physical

designs of components that

make up an enterprise

solution