In order to solve a known problem, a large amount of related information has been collected. How to sort out and express that this information is related to the problem? Use fishbone diagrams. The fishbone diagram can be used to organize the information according to the correlation, so that the elements show the characteristics of clear hierarchy and clear organization. The causal relationship between the collected information and the result of the problem can be clearly marked in the diagram.
■Fishbone diagram: Given a result (topic), a causal expression method that converges to the topic by collecting the main causes.
Note: The inventor is Ishikawa Xin (Japan), also known as Ishikawa Diagram and Causality Diagram.
1. Concept and interpretation
1. The concept
of the model. Since the graphics look a bit like fish bones, they are called fish bone diagrams. Mark the collection results of the problem at the "fish head", and find out the cause of the problem through brainstorming, and use the fish bone diagram. On the fishbone, these factors are listed according to the chances of appearance, forming a graph that is interconnected, clearly structured, and clearly organized. It can intuitively present the causal relationship and help the analyst clarify the thinking and confirm the causal relationship.
Figure 1 Fishbone diagram
2. Model interpretation The
following basic information can be interpreted from the fishbone diagram above,
□Target: the arrangement direction of the fishbone points to the result, and the name of the result is indicated by the name of the fishbone diagram, such as: result=quality degradation problem, Result = Reasons for safe occurrences, etc.
□Main line: A big bone connects the desired factors and points to the result, from left to right.
□Key factors: sort out and classify the collected elements. "Key factor x" is the name of the element collection. Key factors can be divided into several groups. If there are new factors, you can insert them at any time;
□Convergence: All the elements collected are to Convergent
2. Painting method and scene
1. Model drawing method
The main drawing method of fishbone diagram is as follows, see Figure 2.
Figure 2 How to draw a fishbone diagram
□Draw the fish head and large bones to complete the main body; mark the result at the fish head;
□Draw the middle bone, and the middle bone and the large bone form a 45° angle, and mark the name of the cause (classification name);
□Draw the small bone, and Parallel to the big bones, attach specific elements with small granularity;
□The order of the main factor classification: according to the order of the big influence, close to the head of the fish, and the small effect close to the tail;
Example: Combine the information obtained from the survey of "deterioration of engineering quality" and use a fishbone diagram to show the causal relationship.
Through analysis, the problem elements found in the survey are divided into 6 categories (key causes). According to the method that the closer to the "fish head" the greater the impact of the problem, the farther away the less the impact of the problem, the classification and the problem The arrangement of the elements is shown in Figure 3.
Figure 3 Cause and effect analysis of project quality decline
It can be seen from the figure that "1. Material problems" and "4. Technical problems" are the main influencing factors for the result of "decreasing engineering quality".
2. Applicable scenarios
The collected problems and the factors that may cause these problems not only express the causal relationship between them with fishbone diagrams, but also express the severity of the problems through lines and positions.
■Expanding thinking
1) The expression comparison between fishbone diagram and table
can use different forms to express the same conclusion, such as language, table or graph. The graphic expression is the most clear, clear and intuitive, such as: use fishbone diagram and table at the same time To express the method of analyzing the causes of "decreased engineering quality", see Figure 4.
Figure 4 Expression comparison between fishbone diagram and table
□ Picture (a) is expressed in graphics (fishbone diagram)
□ Picture (b) is expressed in tables.
The content of the two is exactly the same, but which way is stronger and more convincing in expressing the "causal-effect" effect of the decline in engineering quality? The conclusion is, of course, that the expression of graphics is the strongest. The reason why graphics is more clear and strong is that the graphics directly show the "logic". The viewer does not need to "read" the logic in the text and tables through thinking, but only By following the logic line, you can "see" the meaning of the graphic expression.
2) The expression difference between fishbone diagram and mind map.
These two diagrams can be used as brainstorming analysis and recording tools to some extent, but there are differences in expression between the two (for reference only).
Figure 5 Mind map and fishbone diagram
□Fishbone diagram
First give a result, and then use this result as the goal to collect information related to the result. This information must support the result. The elements on the same factor line have no distance relationship. There is no clear relationship between all the elements, and the relationship between the elements is not structured.
□The mind map
first gives a topic, and then uses this topic as the starting point to collect information related to the topic in a divergent manner. There is an association relationship between the main node and the child nodes. The elements have a weakly structured relationship, and the distance The farther the center node is, the weaker the correlation between the child nodes.
■The next blog post in this series: How to use the analysis model-3. Parallel chart, collect questions and give answers at the same time
For a more detailed description of the analysis model, please refer to the book "Dahua Software Engineering-Requirements Analysis and Software Design".
