Data Flow Graph creation-test (2)

The first big question in the soft exam is the design of the data flow diagram. This question is a test of the patience, care, and confidence of the reference person.

Concept:

In my personal understanding, the data flow graph is a list of operations (processing) involved by each role (entity) in a system, the documents and materials used and generated during the operation should be recorded ). Starting from the icon of the data flow chart, the chart in the data flow chart contains a rectangle, an elliptical shape, an arrow, and a quadrilateral with a gap.

Rectangle: representing an object

Rounded rectangle: represents the specific processing, which is represented in the form of verbs in the question;

Arrow: indicates the data stream. The name of the data stream must be specified next to it;

Quadrilateral of gaps: information and documents required and generated in the system;

 

TIPS:

Data Flow diagram design usually involves a lot of information. The key information needed for drawing can be found in the information, to a large extent, it is an examination of the examinee's reading ability. So what we need to do is to read the question from start to end and mark all the key information so that the question can be answered later.

The procedure is as follows:

1. mark the key nouns and verbs in the question stem with specific symbols (in my habit, nouns are enclosed in a box; verbs are underlined, and usually followed by nouns after verbs, in line with the verb-object structure, it is necessary to determine whether to add a verb or use it as a noun as a whole based on the requirements of the question; the document and data class should be circled by an elliptical circle );

2. Explain a sentence in the data flow diagram to implement the description in the question stem;

 

Here is an example of the above theory:

Take the May 2013 exam as an example. (For convenience, Red Shadow indicates the box, Blue Shadow indicates the ellipse, and the first and last sections are marked as examples)

A charity and a fund-raising system have been developed to track the collective activities organized for the purpose of raising donations from a business or project to the target group. The main functions of the system are described as follows.

(1) manage volunteers. Send the invitation, follow-up, and work task to volunteers based on the fundraising task; manage the invitation response, volunteer information, working hours, and work results provided by volunteers.

(2) determine the demand for donations and collect the donated gifts (funds and items ). Propose fundraising tasks, send activity requests and donation requests as needed to obtain the funds and items raised.

(3) organize fundraising activities. Determine the activity time range based on the activity request. Search for a venue based on the activity time, that is, send a venue availability request to the venue to obtain the venue availability. Then, based on the promotion time and place, the fund-raising activities will be held based on the corresponding activity information, and funds will be obtained from the Fund-raising agencies and gifts will be given to them. Obtain and process donations, and provide donations. Process interactions with donors, that is:

Enter donor information, Processed and stored in the donor information table; from the donor information tableQuery donor informationTo donorsSend a fundraising requestAnd save the contacts to the linked donor table. Make a donation according to the donation request. After the donation is made, save the donation record to the donation form, process the donation record, save it to the processed donation form, and send a thank-you letter to the donor, follow up the contacts and donation records to send the donation follow-up information to the donors.

Question 1: E1, E2, E3, and E4

First, determine the entity E1. the keyword "donor information/donation" and "acknowledgment letter" can be used to determine the information in the last section. "After the donation request is made, save the donation record to the donation form, process the donation record, and save it to the processed donation form, send a thank-you letter to the donor. The last "send a thank-you letter to the donor" can determine that E1 is the donor. Likewise, the names of E2, E3, and E4 can be determined.

Question 2: Calculate the name processed in 3.1, 3.2, and 3.3, and supplement the missing data stream.

As E4 is the venue, you can locate the related information in "determine the time range of the event based on the activity request. Search for a venue based on the activity time, that is, send a venue availability request to the venue to obtain the venue availability. Then, based on the promotion time and location, the fundraising activities are organized according to the corresponding activity information, and funds are obtained from the fund-raising agencies and gifts are given to them ."

In the circle consisting of 3.3 and E4, you can determine that "Search for venues based on the activity time" should be entered in 3.3. Here is the breakthrough point of this question. Similarly, we can find the answers of 3.2 and 3.4. Because 3.2 does not comply with the principles of the data flow chart, we can also find its input data in the above section, that is, "activity request ". For details, refer to the data stream description in section 3.1.

Finally, we will introduce some common errors in the data flowchart:

1. Input, no output, or black hole;

2. There are outputs without input or miracles;

3. Input data streams cannot be processed to generate output streams or gray holes;

4. The name of the input data stream is the same as that of the output data stream;

There are many similarities between the data flow graph and the object-relationship graph, except that the object-relationship graph is used in the database design, no matter what form of graphics is a kind of sorting of complex system information.

Now, you can try these methods. If you have any questions, please feel free to contact me and look forward to your discussion!

Data Flow Graph creation-test (2)