PLC编程技术包括：经验设计法，逻辑设计法、时序图设计法、顺序控制设计法等编程方法。

PLC programming technique includes experience design method, logic design method, cycle diagram design method and sequential control design method.

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以执行逻辑判断、计时、计数等顺序控制功能。

For the implementation of the logical judgement, timing, sequence number, and other control functions.

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而基于角色的访问控制模型以角色为中介，将用户与权限逻辑隔离，但该模型不能处理有执行顺序的任务；

Role is introduced to separate user and privilege in role-based access control model, but RBAC can't directly control the permission for a sequence of events.

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