什么是逻辑要求？
SRS 应该指定“逻辑需求”，而不是开始“设计”。
我的问题是在 IEEE SRS 文档 (IEEE Std 830-1998) 第 5.3.4 节中说：
5.3.4 逻辑数据库要求
这应该指定要放入数据库中的任何信息的逻辑要求。这可能包括以下内容：
- a) 各种功能使用的信息类型；
- b) 使用频率；
- c) 访问功能
- d) 数据实体及其关系
- e) 完整性约束
- f) 数据保留要求
那么 d) 是否意味着可以绘制 ERD？什么时候在“需求”中将系统指定到这个级别会渗透到“设计”中？
An SRS should specify "logical requirements" but not start "design".
My problem is in the IEEE SRS document (IEEE Std 830-1998) section 5.3.4 says:
5.3.4 Logical database requirements
This should specify the logical requirements for any information that is to be placed in a database. This may include the following:
- a) Types of information used by various functions;
- b) Frequency of use;
- c) Accessing capabilities
- d) Data entities and their relationships
- e) Integrity constraints
- f) Data retention requirements
So does d) mean drawing the ERD is ok? When does specifying the system to this level in REQUIREMENTS bleed in to DESIGN?
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逻辑数据图不定义实际的数据存储。它在概念层面定义了实体。由其他人来弄清楚如何存储这些逻辑实体。
...所以是的，ERD 是可以接受的。
如果您开始指定实际存储需求（哪些数据属于哪些表、数据类型等）而不是仅仅在概念级别定义实体，这种活动将开始渗透到设计中。
A Logical Data Diagram does not define actual data storage. It defines the Entities at a conceptual level. It's up to somebody else to figure out how to store those Logical Entities.
...so yes, an ERD would be acceptable.
This kind of activity would start to bleed into Design if you began to specify actual storage requirements (which data belongs in which tables, data types, etc.) rather than just defining the Entities at the conceptual level.
这是一个非常有用的参考，它打破了逻辑和物理数据库设计之间的差异：
http://www.developer.com/tech/article.php/641521/Logical-Versus-Physical-Database-Modeling.htm
Here is a very useful reference that breaks down the difference between logical and physical database design:
http://www.developer.com/tech/article.php/641521/Logical-Versus-Physical-Database-Modeling.htm
ERD 是逻辑设计。
表列逻辑模式独立于任何物理实现。从表、列（甚至索引）中，您无法确定有关支持该数据库的物理基础架构的任何信息。
物理数据库设计包括表空间、文件系统、介质、日志记录等。
以下是摘要：http://www. revision-zero.org/ological_data_independence
这是一篇论文：http:// /www.sigmod.org/record/issues/9309/design.ps
请注意，“逻辑需求”和“设计”之间没有明确和绝对的划分。原则上，一个是“什么”，另一个是“如何”，但任何规范都存在无限数量的细粒度什么与如何级别。
你可以说“代码”就是设计。我说“代码”是一个逻辑模型，处理该代码的计算机硬件电路是物理设计发生的地方。有人可能会说，表面的硬件指令集只是逻辑设计，而各个门阵列才是物理设计。
An ERD is logical design.
The table-column logical schema is independent of any physical implementation. From the tables, columns (even indexes), you cannot determine anything about the physical infrastructure that supports that database.
Physical database design is tablespaces, filesystem, media, logging, etc.
Here's a summary: http://www.revision-zero.org/logical_data_independence
Here's a paper: http://www.sigmod.org/record/issues/9309/design.ps
Note that there's no clear and absolute division between "logical requirements" and "design". In principle, one is "what" and another is "how", but there's an infinite number of fine-grained what vs. how levels to any specification.
You can say that "code" is design. I say that "code" is a logical model and the circuits of the computer hardware that process that code is where the physical design happens. Someone else can say that the superficial hardware instruction set is just logical design, and it's the individual gate arrays that are physical design.