Modal logic is the logic of necessity and possibility.

　　模態邏輯是關于必要性和可能性的邏輯。

　　We can do quite a lot with modal logic these days.

　　我們這幾天會講很多模態邏輯。

　　Provides consistent, multi-modal access to services.

　　提供對服務的一致性多模式訪問。