Most people planning to develop a software product come across the statement “Good, fast, cheap. Choose two.” This statement clearly shows the limitation of the project management triangle, which does not allow you to do everything in a short time, with a limited budget and with good quality.

大多数打算开发软件产品的人都会遇到“好，快，便宜。 选择两个。” 该声明清楚地表明了项目管理三角形的局限性，它不允许您在短时间内以有限的预算和高质量进行所有工作。

But in negotiations with the client, quite often, I come across the usual desire to spend less money and time, but at the same time get a good product. It almost never happens and when it does the quality often suffers. If you can’t fit everything within the given time and budget then cut down the scope. Therefore, the main question is how, under such conditions, to correctly scale down the scope and get a high-quality product. And functional analysis helps with this.

但是在与客户的谈判中，我常常遇到通常的愿望，即花费更少的金钱和时间，但同时又能获得好的产品。 它几乎永远不会发生，并且当这样做时，质量常常会受到影响。 如果您不能在指定的时间和预算范围内容纳所有内容，请缩小范围。 因此，主要的问题是在这种情况下如何正确缩小范围并获得高质量的产品。 功能分析对此有所帮助。

First, consider the nature of the functional approach

首先，请考虑功能方法的性质

Functional approach — involves considering the product as a set of functions(active verb + measurable noun), rather than as a set of elements and their relationships.

功能方法-将产品视为一组功能(活动动词+可测量名词)，而不是一组元素及其关系。

So, we do not need to split the product into separate components and systems (for example, user authorization, registration, profile, etc.), but we need to understand and describe what functions our product performs for the user. For example, the main function of a messenger is to transfer information from one user to another.

因此，我们不需要将产品分成单独的组件和系统(例如，用户授权，注册，配置文件等)，但是我们需要了解和描述我们的产品为用户执行的功能。 例如，信使的主要功能是将信息从一个用户传输到另一个用户。

For complex analysis, we need to create a functional model — a graphical representation of functions that are logically connected and that consistently reveal the functionality of the analyzed product.

对于复杂的分析，我们需要创建一个功能模型-逻辑连接的功能的图形表示，并始终显示被分析产品的功能。

The FAST method (Functional Analysis System Technique, also known as Function Analysis) helps to build a functional model easily. The method is based on the use of three test questions to simplify the outlining of functions and to check the logical relationship between them.

FAST方法(功能分析系统技术，也称为功能分析)有助于轻松构建功能模型。 该方法基于三个测试问题的使用，以简化功能的概述并检查它们之间的逻辑关系。

• How do you achieve this function?您如何实现此功能？
• Why do you perform this function?为什么要执行此功能？
• When you perform this function, what other functions must you do?执行此功能时，还必须执行哪些其他功能？

The following diagram illustrates how a function is expanded in “How” and “Why” directions in a FAST diagram.

下图说明了如何在FAST图中的“如何”和“为什么”方向上扩展功能。

Start with the main Function:

从主要功能开始：

• Expand the functions in the “How”, “Why” directions在“如何”，“为什么”方向上扩展功能
• Build along the “How” path by asking ‘how is the function achieved’? Place the answer to the right as an active verb and measurable noun sentence.通过询问“如何实现功能”来构建“如何”道路？ 将答案作为活动动词和可衡量的名词句子放在右边。
• Test the logic in the direction of the “Why” path (right to left) by asking ‘why is this function being performed?’通过询问“为什么要执行此功能？”来测试“为什么”路径(从右到左)方向的逻辑。
• When the logic does not work, identify any missing or redundant functions, or adjust the order.当逻辑不起作用时，请确定所有丢失或冗余的功能，或调整顺序。
• To identify functions that happen at the same time, ask “when this function done, what else is being done or being caused by the function?”为了确定同时发生的功能，请问“该功能何时完成，该功能正在执行或由其他原因引起？”
• The higher order functions, functions on the left, describe what is being accomplished. As for the lower order functions, functions on the right, they describe how they are being accomplished.高阶函数(左侧的函数)描述了要完成的工作。 对于低阶功能(右边的功能)，它们描述了它们是如何完成的。
• “When” does not refer to time as measured by a clock, but functions that occur together with or as a result of each other.“何时”不是指时钟所测量的时间，而是指彼此同时发生或相互影响的功能。

Let’s build a simple functional model for a small application, I will not describe all of its functionality, only the main one to show the process in action

让我们为一个小型应用程序构建一个简单的功能模型，我将不介绍其所有功能，而仅介绍主要功能来展示实际的过程

There is a small app that helps you keep in touch with your friends. According to some reports, it takes 50 hours of communication to go from familiarity to friendship. And another 40 hours to become real friends. In General, it takes 200 hours to get close.

有一个小应用程序可以帮助您与朋友保持联系。 根据一些报道，从熟悉到友谊需要50个小时的沟通。 再过40个小时成为真正的朋友。 通常，接近需要200个小时。

The main function of our app is to help a user to keep in touch with their friends. If we start with this to do function analysis, it will look something like this.

我们应用程序的主要功能是帮助用户与朋友保持联系。 如果我们从这里开始进行功能分析，它将看起来像这样。

结论 (Conclusion)

With this approach, we start by understanding how all the various functions of a product, service or project work together to create value in the mind of the final customer. This diagram helps teams find a critical path to development, set function values based on consumer opinions, compare function values with their costs, and choose functions to improve. In addition, this functional model can be easily transformed into a user stories map and divided into releases.

通过这种方法，我们首先了解产品，服务或项目的所有各种功能如何共同发挥作用，从而在最终客户的心中创造价值。 该图可帮助团队找到关键的开发路径，根据消费者的意见设置功能值，将功能值与其成本进行比较，并选择要改进的功能。 此外，该功能模型可以轻松转换为用户故事地图并分为发行版。

Of course, with a large product, the process will be larger and take longer to build, but this will help to find out what is really important. What’s going to make it into the initial release?

当然，对于大型产品，该过程将更大并且需要更长的构建时间，但这将有助于找出真正重要的内容。 是什么使它成为初始版本？