PSAC中的overview与summary——DO-178B/ED-12B学习笔记之十二

PSAC中的overview与summary
——DO-178B/ED-12B学习笔记之十二

DO-178B/ED-12B的11.1是对PSAC的要求，其中出现overview与summary的段落是：

11.1.a	System overview: This section provides an overview of the system, including a description of its functions and their allocation to the hardware and software, the architecture, processor(s) used, hardware/software interfaces, and safety features.(笔者注：DO-178C补了features和句号)
11.1.b	Software overview: This section briefly describes the software functions with emphasis on the proposed safety and partitioning concepts, for example, resource sharing, redundancy, multiple-version dissimilar software, fault tolerance, and timing and scheduling strategies.
11.1.c	Certification considerations: This section provides a summary of the certification basis, including the means of compliance, as relating to the software aspects of certification. This section also states the proposed software level(s) and summarizes the justification provided by the system safety assessment process, including potential software contributions to failure conditions.
11.1.d	Software life cycle: This section defines the software life cycle to be used and includes a summary of each software life cycle and its processes for which detailed information is defined in their respective software plans. The summary explains how the objectives of each software life cycle process will be satisfied, and specifies the organizations to be involved, the organizational responsibilities, and the system life cycle processes and certification liaison process responsibilities.

词典中关于overview与summary的解释是很相近的。但是，DO-178B/ED-12B对于这四个对象分别使用了overview与summary，是有一定的理由的。笔者的理解是：
a) 11.1.a与11.1.b所要描述的内容，在11章的其他软件生存周期数据中没有出现；
b) 11.1.c要描述的内容，在系统安全性评估过程中已经出现过；
c) 11.1.d要描述的内容，将在相应的软件计划中有更详细的描述。

因此，在编写11.1.a与11.1.b相关内容时应注意整体性，而在编写11.1.c与11.1.d相关内容时要注意与其他文件的一致性。

以下是一个解释overview与summary差异的帖子：
http://forum.wordreference.com/showthread.php?t=26002
Re: overview or summary

Overview
1. A broad, comprehensive view; a survey
2. A summary or review

Summary
1. Presenting the substance in a condensed form; concise: a summary review.
2. Performed speedily and without ceremony: summary justice; a summary rejection.
3. A presentation of the substance of a body of material in a condensed form or by reducing it to its main points; an abstract.

Here is what Dictionary.com says. Pretty similar! But, from my person experiences, a summary tends to be more abbreviated than an overview. (An overview providing slightly more detail.) IMHO