shall、should、may、can的含义和使用（IEEE

The word shall is used to indicate mandatory requirements strictly to be followed in order to conform to the Specification and from which no deviation is permitted (shall equals is required to).

shall 一词用于表示为符合规范而必须严格遵守的强制性要求，并且不允许偏离（shall equals is required）。

The use of the word must is deprecated and shall not be used when stating mandatory requirements; must is used only to describe unavoidable situations.

必须 一词已被弃用，不得在说明强制性要求时使用； must 仅用于描述不可避免的情况。

The use of the word will is deprecated and shall not be used when stating mandatory requirements; will is only used in statements of fact.

will 一词已被弃用，不得在陈述强制性要求时使用； will 仅用于事实陈述。

The word should is used to indicate that among several possibilities one is recommended as particularly suitable, without mentioning or excluding others; or that a certain course of action is preferred but not necessarily required; or that (in the negative form) a certain course of action is deprecated but not prohibited (should equals is recommended that).

应该一词用于表示在多种可能性中推荐一种特别合适，不提及或排除其他； 或者某种行动方案是首选但不一定是必需的； 或者（以否定形式）不赞成但不禁止某些行动方案（建议应该等于）。

The word may is used to indicate a course of action permissible within the limits of the Specification (may equals is permitted to).

可能一词用于表示在规范范围内允许的行动过程（可能等于被允许）。

The word can is used for statements of possibility and capability, whether material, physical, or causal (can equals is able to).

can可以用于可能性和能力的陈述，无论是物质的、物理的还是因果关系（可以等于能够）。