There is a special form for boolean formulas called "Conjunctive Normal Form" (CNF). A problem in this form consists of clauses connected with and operators, where each clause only contains variables connected with or operators. The variables can appear negated, but only variables can be directly negated, something like !(a && b) is not allowed. An example boolean formula in CNF form is:
变化三：存储技术，持续演进需求分层与周期重构，倒逼存储技术进入产业化迭代的快车道。
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Knowledge Retrieval（规范/PRD/接口文档），详情可参考下载安装 谷歌浏览器 开启极速安全的 上网之旅。
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