[Software Engineering General Review] Chapter 2 Feasibility Research (Feasibility Analysis)

1. The purpose of the feasibility study (short answer questions)

Determine whether the problem can be solved in the shortest possible time with the least cost. (Determine whether the project can be launched in the shortest time) (The purpose of the feasibility study is not to solve the problem, but to determine whether the problem is worth solving)

2. Contents of Feasibility Study

2.1 Technical Feasibility

2.2 Economic feasibility

Low-cost, medium-cost, high-cost systems

2.3 Operation Feasibility

2.4 Social Feasibility

3. Tasks of the feasibility study (short answer questions)

The essence of feasibility study: a greatly compressed and simplified system analysis and design process, that is, a system analysis and design process carried out in a relatively abstract manner at a higher level.

1. First, further analysis and clarification of the problem definition is required.
2. Analysts should derive a logical model of the system. And starting from the system logic model, explore several alternative main solutions (that is, system implementation schemes).

Each solution should be carefully studied for its feasibility. When analyzing whether an alternative solution is feasible, three aspects should be considered: technology, economy, operation, and choice.

1. Technical feasibility: Whether the existing technology, resources and limitations can support and realize the function and performance of the system. Mainly technical risk issues.
2. Economic feasibility: conduct cost estimation and benefit evaluation to determine whether the project is worth developing
3. Social feasibility: mainly refers to whether the system can run after development, and whether there are problems in contract, liability, infringement, user organization and management, etc.
4. Choice: compare, evaluate, and choose among various alternatives

4. System flow chart

A system flow diagram is a traditional tool for schematically depicting a physical system. Its basic idea is to use graphical symbols to describe each component (program, document, database, human process, etc.) that makes up the system in the form of a black box

5. Data flow diagram (do not draw this diagram)

1. A data flow diagram (DFD) is a graphical technique that depicts the flow of information and the transformations undergone by data as it moves from input to output. A data flow diagram is a graphical representation of the logical functionality of a system.
2. There are no specific physical components in DFD, it just depicts the logical process of data flowing and being processed in software.

Four basic symbols of data flow diagram

1. A square (or cube) represents the source or destination of the data;
2. Rounded rectangles (or circles) represent processing of transformed data;
3. An open rectangle (or two parallel horizontal lines) represents data storage;
4. Arrows indicate data flow, the direction in which specific data flows.

6. Data Dictionary DD (short answer questions, no big questions, basic concepts)

Definition (short answer questions) : A data dictionary is a collection of information about data, that is, a collection of definitions for all elements contained in a data flow graph.

Contents of the data dictionary: data streams, data stream components (data elements), data storage, processing

symbol	meaning	example
=	is defined as
+	and	x = a + b
[…,…]	or	x = [a,b]
[…I…]	or	x = [aIb]
{…}	repeat	x = {a}
m{…}n	repeat	x = 3{a}10
(…)	optional	x = (a)
“…”	fundamental element	x = “a”
…	Joiner	x = 1…9

The method of defining data: Decompose the data from top to bottom. Generally speaking, when the decomposition reaches the elements that do not need to be further defined, and everyone related to the project is clear about the meaning, the decomposition process is completed.
The purpose of the data dictionary:

1. As a tool in the analysis phase (most important).
2. A tight and consistent set of definitions established in the data dictionary will go a long way toward improving communication between analysts and users, and will therefore eliminate many possible misunderstandings.
3. This tightly consistent set of definitions for data also helps improve communication between different developers or different development groups.
   Description of the content of the data dictionary
   In the compilation of the data dictionary, the symbols most often used by analysts to describe the content or data structure are as follows

6.1 Examples

6.1.1 A programming language stipulates that an identifier is composed of letters, numbers or underscores, and the length does not exceed 8 characters, and it is stipulated that the first character must be a letter or an underscore.

Identifier = first character + string
first character = [letter | underscore]
string = 0 { character } 7
characters = [letter | number | underscore]
letter = a...z
number = 0...9

6.1.2 Telephone numbers include mobile phone numbers and landline phone numbers. Mobile phone numbers consist of 11 digits, the first of which is a non-zero digit. A landline telephone number consists of 8 digits, the first digit of which is a non-zero digit. (emphasis)

Phone number=[mobile number|landline number]
mobile number=8 digits
landline number=11 digits
mobile number=non-0 number + 7-digit
landline number=non-0 number + 10-digit number
7-digit number=7 {number}7
10-digit number=10{number}10
number=[0|1|2|3|4|5|6|7|8|9]
non-zero number=[1|2|3|4|5 |6|7|8|9]

6.1.3

Passbook=account name+station number+account number+account opening date+property+(password) +1{access line}50
account name=1{letter}24station
number='001"..."999"
account number="0000001" ..."9999999"
account opening date = year + month + day
nature = "1" ... "6"
seal code = "0"

Access Row = Date + Summary + Expenditure + Deposit + Balance + Operation + Review
Date = Year + Month + Day
Summary = 1 {Letter} 4
Expense = Amount
Deposit = Amount
Balance = Amount
Operation = 4 {Number} 4
Review =4{Number}4Amount
="0000000.01"..."9999999.99"

7. Cost/benefit analysis (calculated without cost estimates)

7.1 Purpose of benefit analysis

Analyzing whether it is cost-effective to develop a particular new system from an economic point of view can help to make the correct decision whether to invest in this development project.

7.2 Performance of economic benefits

Economic benefits typically manifest as reduced operating expenses or increased revenue

The first step in a cost/benefit analysis is to estimate the development costs, operating expenses, and economic benefits that the new system will bring

1. Operating costs depend on the operating costs of the system (number of operators, working hours, materials consumed, etc.) and maintenance costs.
2. Economic benefit of the system = increased revenue due to the use of the new system + operating costs saved by the use of the new system.

1. Time value of money: The time value of money is usually expressed in the form of interest rates.
2. Payback period: The time required for the cumulative economic benefits to equal the initial investment.
3. Net income: the difference between the cumulative economic benefits (converted into present value) and investment of the system within the entire life cycle.
4. Return on investment rate: measure the size of investment benefits, and it can be compared with the annual interest rate.

7.3 Methodology for cost/benefit analysis (not calculated)

cost

Cost of hardware and equipment
Cost of developing system Cost of
system installation, operation and maintenance Cost
of personnel training

benefit

Economic Benefits
Social Benefits

7.3.1 Time value of money

7.3.2 Payback Period

Usually the payback period is used to measure the value of a development project. The so-called payback period is the time required to make the accumulated economic benefits equal to the initial investment.

7.3.3 Net Income

Another economic indicator to measure the value of a project is the net income of the project, that is, the difference between the cumulative economic benefits of the system (converted into the present value) and the investment within the entire life cycle.

7.3.4 Return on investment

The investment return rate is used to measure the size of the investment benefit, and it can be compared with the annual interest rate. It is the most important reference data when measuring the economic benefit of the project.