Feasibility study

Task feasibility study

1, the purpose of the feasibility study is not the solution, but rather determine whether the problem is worth solving

2, in general, at least from the feasibility study the following three aspects:

Technical feasibility
Economic feasibility
Operational feasibility

3, the length of time required for a feasibility study depends on the size of the project, 5% in general, the cost of the feasibility study but the expected total cost of the project · 10%

System flow chart

1, the system is a flowchart depicting an overview of the physical system to a conventional tool. Expression system is a flowchart in the case of data flow between the various components of the system, not the control procedure for data processing, and so even though some of the same symbols and program flow diagram form in line with the flowchart of the system, but he is physical data flow rather than program flow chart of FIG.

2, a flowchart of the system in line and system symbols

3, a system simple column flowchart solid:

Data flow diagram

1, a data flow diagram (the DFD) is a graphical technique, which depicts the flow of information from the input data and the process moves to the output of the transformation is subjected.

2, common symbols and diacritics

3, the data stream in four symbolic

Squares represent the data source or end
Rounded rectangles represent processing transformed data
Storing data representative of a rectangular opening
Arrows indicate data flow, i.e. the flow direction of the specific data

4, a simple example shows how the data flow diagram Videos

eg: suppose Purchasing a factory orders report needs a daily report by ordering part number, listed in the table all the required reorder parts. For each need to reorder parts should list the following data: part number, part name, number of orders, current prices, the main supplier of secondary suppliers. Parts storage or a library called transaction by CRT terminal on the warehouse in the transaction reported to the ordering system. When a certain number of stock inventory of parts is less than the threshold should be ordering again.

Description of the problem can be extracted from the four components in the data flow graph: first consider the source and the end-point data from the above description of the system can know "Purchasing orders require a report every day," "appear in the repository by CRT terminal transactions reported to the ordering system, "so buyers are end data, and the data source is a warehouse manager.
Once again, read the description of the problem, "the report purchasing needs." Therefore, there must be a process for producing the report. The consequences of the transaction is to change parts inventory, but nothing changed data are processed, and therefore the processing of transactions is another treatment. Note that, in the description of the problem and need not explicitly mention the transaction processing, but it can be seen by analyzing this need.
考虑数据流和数据存储系统把订货报表送给采购部，因此订货报表是一个数据流；事务需要从仓库送到系统中，显然事务是另一个数据流。产生报表和处理事务这两个处理在时间上明显不匹配——每当有一个事务发生时立即处理它，然而每天只产生一次订货报表。因此，用来产生订货报表的数据必须存放一段时间，也就是应该有一个数据存储。
分析结果
把数据流图的4种成分都分离出来以后（上图所示），就可以着手画数据流图了
把基本系统模型细化，描绘系统的主要功能
对功能级数据流图中描绘的系统主要功能进一步细化