Tài liệu Module 5: Business Solution Logical Design pptx

Module 5: Business Solution Logical
Design

126 Module 5: Business Solution Logical Design




Module Overview

Module 3: A Services-based
Approach to Solution Design
Module 4: Business Solution
Conceptual Design
Module 5: Business Solution
Logical Design
Module 6: Beginning Physical
Design
Module 1: Course Overview
Module 2: Solution Design Using
the MSF
Module 7: Selecting Solution
Technologies
Module 8: Solution Design and the
Component Object Model
Module 9: Designing Solutions with
Microsoft Technologies
Module 10: Completing the
Physical Design
Module 11: Designing the

Presentation Layer
Module 12: Introduction to
Functional Specifications
Designing Business
Solutions
Logical Design
Basics
Activity 5.2: Identifying
Business Objects and Services
Logical Design Analysis:
Attributes and Relationships
Review
Activity 5.1: Risks of
Skipping Logical Design
Logical Design
Process
Logical Design Analysis:
Services and Objects
Activity 5.3: Identifying
Attributes and Relationships
Logical Design Analysis:
Rationalization
Activity 5.4: Logical
Design Verification
Module 5: Business
Solution Logical
Design
Module 5: Business Solution Logical Design 127

!
!!
! Overview
In this module
In this module
"
Logical Design Basics
"
Activity 5.1: Risks of Skipping Logical Design
"
Logical Design Process
"
Analysis: Business Objects and Services
"
Activity 5.2: Identifying Business Objects and Services
"
Analysis: Attributes and Relationships
"
Activity 5.3: Identifying Attributes
and Relationships
"
Logical Design Rationalization
"
Activity 5.4: Logical Design Verification
"
Review

The second phase of the MSF Design Process is logical design. Logical design
begins after conceptual design has started, when the project team agrees that
there is sufficient information to begin the logical design. A good logical design
depends greatly on a good conceptual design.
Because the MSF Design Process is an evolutionary, as well as iterative,
process, logical design will greatly impact your physical design and provide
feedback into the conceptual design.
In this module, you will learn about the logical design phase of the MSF
Process Model. First, you will learn the basics of logical design — where it fits
into the MSF Process Model, its steps, and the tasks and outputs of the logical
design phase. Then you will learn about logical design in greater detail through
the use of examples and activities based on the Ferguson and Bardell case
study.
After completing this module, you will be able to:
"
Explain the need for logical design in the process of designing a business
solution.
"
Describe the role of logical design in the MSF Design Process.
"
Describe the steps of logical design.
"
Identify the principles of modular design.
"
Assess the impact of implementation consideration on the logical design.
"
Design the objects and services of a business solution.
"
Derive a logical design for a business solution from a conceptual design.

Slide Objective
To provide an overview of
the module topics and
objectives.
128 Module 5: Business Solution Logical Design




!
!!
!

Logical Design Basics
In this section
In this section
"
Logical Design in the Design Process
"
Logical Design: The Search for Organization
"
Goals of Logical Design
"
Perspective of Logical Design
"
Perspective Captured in Business
Object Models
"
Clarifying Logical Design
"

Value of Logical Design


Logical design is arguably the most difficult concept of the design process to
grasp. Both conceptual and physical design can often be understood intuitively;
however, the transition between them — logical design — is often confusing.
To mitigate that confusion, you will learn about the basics of logical design
before learning about the process.
In this section, you will learn how logical design can be considered a search for
organization. You will learn what logical design is and what it is not, as well as
the value that logical design brings to the overall design.
Slide Objective
To provide an overview of
this section.
Module 5: Business Solution Logical Design 129




Logical Design in the Design Process
Conceptual Design
Scenarios
Logical Design
Physical Design
Components,
User Interface, and
Physical Database
Services and Objects,
User Interface, and
Logical Database

Logical design is the second phase of the MSF Design Process Model. Logical
design involves clearly defining the solution in terms that everyone on the
project team can understand. The inputs to logical design are the scenarios of
conceptual design. The output of logical design is the business object model,
which serves as the basis for physical design.
Slide Objective
To position the logical
design phase in relation to
the design process.
Lead-in
As you learned in Module 2,
logical design is the second
phase in the MSF Design
Process.
130 Module 5: Business Solution Logical Design




Logical Design: The Search for Organization
"
Definition
The process of describing the solution in
terms of the organization, structure, syntax,
and interaction of its parts
"
Purpose
To apply services-based organizing

principles to lay out the structure of the
solution and define the relationships among
its parts
"
Output
A set of business objects with
corresponding services, attributes, and
relationships; a high-level user interface
design; and a logical data model
Logical Design
Services and Objects,
User Interface, and
Logical Database


Logical design defines the constituent parts of a system and provides the
organizing framework that holds all of those detailed parts together. It
illustrates how the system is put together and how the system interfaces with
the outside world (users and other systems).
Logical design can be likened to the second stage in designing a house. In the
first stage, the customer and the architect collaborated on a rough sketch and a
short list of needs and requirements, similar to the scenarios in conceptual
design. Now, in the second stage, the architect concentrates on creating the
floor plan by organizing architectural elements such as doors and windows,
roofs and patios, and rooms and their spatial relationships into a harmonious
whole.

This module deals only with the first output — a set of objects with
corresponding services, attributes, and relationships. The high-level user
interface design is covered in Module 11: Designing the Presentation Layer,

and the logical data-store design is covered in Course 1609: Designing Data
Services and Data Models.

Slide Objective
To give an overall
description of logical design.
Lead-in
Logical design is considered
“the search for organization”
because it takes the
scenarios provided by the
conceptual design and
attempts to organize the
requirements into a solution.
Note
Module 5: Business Solution Logical Design 131




Goals of Logical Design
"
Transform the conceptual design into a coherent view of
the entire solution
"
Describe the solution in terms of the organization,
structure, syntax, and interaction of its parts
"
Provide the basis for physical design efforts

Logical design plays a pivotal role in systems development and provides a
strong link between the technical and nontechnical team members. It provides a
structure that allows independent team members to work effectively in parallel
while coordinating with external projects and architects. The logical design
describes the system and the solution in broad terms. This description includes
details about the organization, structure, syntax, and interaction of the elements
of the solution. Logical design defines the system elements, their boundaries,
the services they provide, and their interactions and dependencies.
Any project team member should be able to look at the logical design and
identify the important structures of the solution, the objects in the system, and
how the objects interact to solve the problem.
The team might also uncover additional user or business process requirements.
If so, the team must update and iterate through the scenarios and conceptual
design, identifying how those changes affect system behavior over the life of
the project.
Slide Objective
To describe the overall
goals of the logical design
phase.
132 Module 5: Business Solution Logical Design




Perspective of Logical Design
Conceptual
The logical design
perspective is from the
point of view of the

project team
Logical
Physical
Business
Solution


When the project team moves from conceptual to logical design, a fundamental
shift in perspective occurs. During conceptual design, the team defines the
business problem by communicating with the user and business communities.
During logical design, team members work together to define the organization,
structure, and syntax of the resulting solution. They derive logical design from
the scenarios of conceptual design, thus providing structure while preserving
the semantics of the problem captured in conceptual design.
Slide Objective
To highlight that the logical
design of the solution is
based on the project team’s
perspective of the solution.
Lead-in
While conceptual design
viewed the problem from the
perspective of the user,
logical design views the
problem from the
perspective of project team.
Module 5: Business Solution Logical Design 133

Perspective Captured in Business Object Models
"
Defines the parts of the system
"
Describes the organization of the parts
"
Describes the relationship of the parts — how they
coordinate and cooperate
"
Provides
$
Improvements in how the parts of the system operate
$
A common view of the solution among team members
$
A baseline to evaluate physical opportunities


The business object model is a major deliverable of logical design. It defines
the parts of the system, such as the object, services, and attributes.
The business object model also describes the organization of the parts within
the system and the relationships among the parts.
Overall, the business object model provides several benefits, including
improvements to how the parts of the system operate, a common view of the
solution among team members, and a baseline to evaluate physical
opportunities.
Slide Objective
To introduce the business
object model and its use

during logical design.
Lead-in
Logical design is about the
business object model. It is
used to define the parts of
the system, their
organization, and their
relationship to each other.
134 Module 5: Business Solution Logical Design




Clarifying Logical Design
Logical design is not
The technology solution
Optimized for a selected physical
model
But it enables you to
Specify the business needs that
technology must support
Reveal technology constraints and
opportunities
Identify appropriate technologies
that you can implement
Identify possible adjustments in the
logical design due to infrastructure
and deployment issues

Logical design should be independent of technology and physical
implementation. The primary focus is on what the system needs to do, which is
explained by an organized structure of cooperating elements. It is important that
the system be completely understood by all stakeholders before making the
commitment to technology.
In reality, certain physical constraints or opportunities should be considered in
logical design in order to validate whether the design can be implemented (or
whether it is flexible across multiple required environments). In effect, logical
design is as independent of technology as is prudent.
Decisions regarding technology are made during physical design. It is important
to distinguish between logical and physical design to separate system-behavior
issues from system-implementation issues. Implementation constraints should
be considered only after the project team verifies that the essential requirements
of the business and users have been incorporated into the logical design. This
approach does not establish a technical direction until the solution is well
understood and documented.
If physical constraints or details are discovered while the team is focusing on
logical design, that information should be taken into account during the logical
design. The logical design is the base on which evaluations and decisions about
feasibility and implementation alternatives for the physical design occur.
Slide Objective
To clarify what logical
design really is and to
dismiss some possible
assumptions.
Lead-in
The following table should
help clarify what logical
design is and what it is not.
Module 5: Business Solution Logical Design 135

Value of Logical Design
"
Creates a common view of the solution among project
team members
"
Manages complexity
"
Provides organizing structure, allowing parallel effort
"
Uncovers any errors and inconsistencies in conceptual
design
"
Eliminates redundancy and identifies potential reuse
"
Improves the operation of the parts of the system
"
Provides a foundation for physical design


The inability to deal successfully with complexity has resulted in many project
failures. Complexity leads to incomplete understanding, which leads to
confusion, which leads to poorly specified and inadequate designs. Many
business processes that are being supported through information technology are
inherently complex, and it is a mistake to attempt to ignore the inherent
complexity of a given problem. The preferred path is to manage the complexity.
The key to managing complexity is organizing the solution and suppressing

unnecessary details.
Logical design plays a pivotal role in systems development. It provides a strong
link between the technical and nontechnical members of the team. Logical
design provides the organization and structural rules required for independent
team members to work effectively in parallel, and it provides the basis for
effective coordination with external projects and architects.
Any solution is only as good as its constituent components. By setting
boundaries and interfaces, the design takes on more identifiable characteristics
and gives the design group a basis for communication.
By the time a representative logical design is complete, any errors in judgment
or logic in the conceptual design should be clear. These discrepancies can be
corrected before the design becomes a production solution.
By looking at the solution as a series of components and services, it is easier to
identify portions of the design that act similarly. By taking this view, the project
team can identify which components and services may be reused, which will
ultimately help make the design more efficient and maintainable.
The foundation that the logical design provides can be used as the fundamental
building block for the physical design. By looking at the design as a modular
system of components, the project team can determine the location and
attributes of the components’ physical representations.
Slide Objective
To explain the benefits of a
good logical design and how
it helps the overall success
of the project.
Lead-in
A good logical design is
important to the success of
the project. The following
are some of the benefits

gained by having a good
logical design.
136 Module 5: Business Solution Logical Design




Activity 5.1: Risks of Skipping Logical Design


In this activity, you will take part in a class discussion to identify the possible
risks of not doing logical design.
After completing this lab, you will be able to:
"
Articulate the value of doing logical design and the risks of not doing
logical design.

Slide Objective
To introduce the activity.
Module 5: Business Solution Logical Design 137




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Logical Design Process
In this section

In this section
"
Logical Design and the MSF Process Model
"
Logical Design Steps
"
Deliverables of Logical Design


In this section, you will learn about when the logical design stage takes place in
the MSF Design Process Model. You will also learn of the separate steps that
make up the logical design stage and the deliverables of those steps.
Slide Objective
To provide an overview of
this section.
138 Module 5: Business Solution Logical Design




Logical Design and the MSF Process Model
Vision
Approved
Vision
Approved
Project Plan
Approved
Project Plan
Approved
Baseline

Conceptual Design
Logical Design
Physical Design
Logical design begins before the team baselines conceptual
design and ends before the team reaches the Project Plan
Approved Milestone


Although logical design is dependent on the products of conceptual design,
logical and conceptual (and physical) design can be carried out concurrently.
Logical design can begin any time after the conceptual design has begun. As the
scenarios become available, logical design can continue on an incremental
basis.
The results of logical design, as with conceptual and physical designs, become
part of the functional specification.
The logical design may go through several iterations while details continue to
be added to the functional specification through elements in physical design or
changes in the conceptual design. As new elements are introduced or needed
that were not included in the logical design, the design should be revisited.
Iteration occurs until there is consensus that the logical design is sufficiently
developed to be baselined. The baseline is an interim milestone and serves as a
reference point for change management.
Slide Objective
To show where conceptual
design fits into the project
life cycle.
Lead-in
Logical design begins after
conceptual design has
begun and ends before the

team reaches the Project
Plan Approved Milestone.
Module 5: Business Solution Logical Design 139




Logical Design Steps
Analysis
Baseline
Logical Design
Baseline
Rationalization
Analysis
Rationalization
Baseline
Although portrayed
sequentially, these
steps are iterative and
overlapping
Logical Design


The logical design phase has two steps and associated baselines:
"
Analysis
• Identifying objects and services
• Identifying attributes and relationships

"

Rationalization
• Verifying objects
• Identifying implied objects and scenarios

The rationalization baseline leads to the baseline of the logical design.
Slide Objective
To introduce the three
activities that make up
conceptual design.
Lead-in
The logical design stage is
composed of two separate
steps: analysis and
rationalization.
140 Module 5: Business Solution Logical Design




Deliverables of Logical Design
"
Business object model
$
Business objects
$
Services
$
Attributes
$
Relationships

The business object model includes the business objects, services, attributes,
and relationships. The business object model is the primary deliverable of
logical design.
Slide Objective
To identify the outputs of
logical design.
Lead-in
At the logical design
baseline, the project team
will have a business object
model.
Delivery Tip
Each of these components
of the business object model
will be discussed in detail
later in the module.
Module 5: Business Solution Logical Design 141




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!

Analysis: Business Objects and Services
In this section
In this section

" Deliverables of the Analysis Baseline: Part 1
" Business Objects
" Identifying Business Objects from Scenarios
" Examples of Business Objects
" Services
" Identifying Services from Scenarios
" Examples of Services


Logical design is the transition between the scenarios of conceptual design and
the actual physical design. This transition involves building some intermediary
models.
In this section, you will learn about some of the building blocks of logical
design: modules, services, and objects. You will practice using these concepts
through examples and activities.
Slide Objective
To provide an overview of
this section.
142 Module 5: Business Solution Logical Design




Deliverables of the Analysis Baseline: Part 1
Analysis
Baseline
Analysis
Task
Identify business objects
Identify services

Identify attributes
Identify relationships
Model business objects
Deliverable
List of business objects
List of services
List of attributes
List of relationships
Business object model


At this point in logical design, the set of objects and services has been through
several iterations of discovery, but it may still need refining. This will be
discussed in the next module, Module 6: Logical Design Rationalization.
Slide Objective
To explain the content and
context of the analysis
baseline.
Lead-in
The analysis baseline
signifies the end of the
analysis step of the logical
design phase.
Module 5: Business Solution Logical Design 143




Business Objects
An encapsulation of services and attributes

that is used to organize the solution and
reduce its complexity
Services
Business
Object
Attributes


Objects are the people or things described in the scenarios. These objects
become the basis for determining services, attributes, and relationships.
Slide Objective
To define a business object.
144 Module 5: Business Solution Logical Design




Identifying Business Objects from Scenarios
Business Objects are
" People or things that the
scenarios describe
" The basis for identifying
attributes and
relationships
Bill Time
$
Consultant looks up client
name
$
System retrieves client

number according to
name requested
$
Consultant bills time to the
client number
Scenarios
Business
objects
People or
things


A variety of methods can be used to identify the relevant objects necessary for
the solution. The most straightforward technique is to grammatically inspect the
scenario models described in the conceptual design. In each of the models, look
for nouns in the scenario descriptions to help identify objects (nouns may be
hidden by the use of passive voice).
Grammatical inspection, or noun-verb analysis, of the scenarios creates a direct
map to candidate objects and services. A sentence with a subject, verb, and
direct object reveals two potential business objects: the subject and the direct
object. Generally, if the noun or direct object represents something in which the
system or the business has an interest in or acts upon, it is a likely candidate
object.
A noun could also identify an attribute of an object rather than the object itself.
For example, the noun "name" is most likely an attribute of some other object,
such as a person or a guest. True objects usually contain more than one
attribute. In addition, these attributes should not all be derived attributes.
Some objects may not be specifically stated in any of the models of the
scenarios, even though these objects may be necessary to complete the business
activities that the scenarios describe. Examples of these types of objects are

structures, other systems, devices, things or events remembered but not
contained in the scenario, roles played, operational procedures, locations or
sites, and organizational units. To identify missing objects, think about the
scenario in terms of needed or required remembrance (or persistence of
information) and needed or required behavior that has no object as an owner.
Slide Objective
To present the student with
a method for determining
objects within a system.
Lead-in
Objects are derived from the
scenarios developed in
conceptual design.
Module 5: Business Solution Logical Design 145




Examples of Business Objects
Sample scenario text
$
Consultant looks up client name
$
System retrieves client number according to name requested
$
Consultant reviews prior billings to client
$
Consultant bills time to the client number
Business
object

Business
Business
object
object
Defining reason
Defining reason
Defining reason
Consultant
Consultant
Performs actions within the system. Can be represented
abstractly.
Performs actions within the system. Can be represented
abstractly.
Client
Client
Receives the result of actions performed by a consultant. Can
also be represented abstractly.
Receives the result of actions performed by a consultant. Can
also be represented abstractly.


"
In the process of designing a solution for the Ferguson and Bardell case
study, a business object model will be created.
Objects in this design are defined as people, places, systems, or things. When
looking at the task sequence, try to derive what is acted upon rather than what is
being done.
"
In the slide, the task sequences focus primarily on two people: consultant
and client.

"
The consultant is a business object because a consultant performs actions
within the system.
"
The client is the recipient of actions performed by the consultant. Thus, in
this context, the client is a business object as well.
Slide Objective
To provide the student with
examples of objects.
146 Module 5: Business Solution Logical Design




Services
A unit of application logic that includes
methods for implementing an operation,
function, or transformation
Services


A service is a fundamental unit that provides a discrete capability. A service is a
specific behavior that a business object is responsible to perform — an
operation, a function, or a transformation that can be applied to or implemented
by an object. Services define a business object’s behavior. They can enforce
business rules, perform calculations or manipulations on data, and store or
retrieve information. In brief, a service can perform any activity that can be
described by a set of rules.
Slide Objective
To define a logical design

service.
Module 5: Business Solution Logical Design 147




Identifying Services from Scenarios
Services are actions that
objects perform
Bill Time
$
Consultant looks up client
name
$
System retrieves client
number according to
name requested
$
Consultant bills time to the
client number
Scenarios
Services
Actions


Verbs in the usage scenarios are the best indicators of services, although not
every verb in the scenario will be identified as a service.
Some of the verbs in the sentences will represent associations between objects
rather than a service of a single object. This information is also important and
will be discussed in the next section, Analysis: Attributes and Relationships.

Consider the object’s responsibility. What knowledge does the object maintain,
and what actions can it perform? Keep behavior with related information; if an
object keeps information, it also has to perform the operations upon this
information.
The services that are identified must be assigned to an object, which is the
recipient of the action or is responsible for carrying it out; this will usually be
the grammatical subject or direct object in the sentence containing the service
verb. If it is difficult to decide to which object a service belongs, the different
possibilities can be examined by walking through the scenario. This often
reveals the most natural or most efficient association of a service to an object.
State the capabilities and responsibilities of a service as generally as possible.
Preferably use only active verbs. A service should be identified by a clear,
unambiguous name. Trouble identifying a service and creating a name often
indicates that the functionality or purpose of the service isn’t clear and may
require additional investigation in the conceptual design.
Slide Objective
To show the process of
deriving services from
scenarios.
Lead-in
Scenarios provide the
groundwork for identifying
services.
148 Module 5: Business Solution Logical Design




Examples of Services
Candidate services

$
Find client
$
Retrieve client number
$
View billing history
$
Assign hours
Sample scenario text
$
Consultant looks up
client name
$
System retrieves
client number
according to name
requested
$
Consultant reviews
prior billings to client
$
Consultant bills time
to the client number


The slide shows some examples that describe the concept of a service through
the use of the Ferguson and Bardell case study.
Consultant looks up client name corresponds to a candidate service of find
client.
System retrieves client number according to name requested corresponds to a

candidate service of retrieve client number.
Consultant reviews prior billings to client corresponds to a candidate service of
view billing history.
Consultant bills time to the client number corresponds to a candidate service of
assign hours.

Slide Objective
To provide an example of
identifying services from a
scenario.
Lead-in
The following are some
examples of possible
services that correspond to
actions performed in the
scenarios.
Module 5: Business Solution Logical Design 149




Activity 5.2: Identifying Business Objects and Services


In this activity, you will identify the business objects and services contained in
the scenario that the instructor provides.
First, you will analyze the usage scenario for potential business objects. These
candidate business objects are the logical constructs that help identify the
services, attributes, and relationships of the future solution.
Next, you will analyze the usage scenario for potential services.

Finally, you will extend the analysis to identify hidden objects and services.
After completing this activity, you will be able to:
"
Analyze a usage scenario and determine candidate business objects and
services for use in the solution design.

Slide Objective
To introduce the activity.