UML 状态机中是否可以有多个活动状态
Can there be more than one active state in a UML state machine
我理解在复合状态下可以同时存在正交区域运行。
在 UML 状态机中，任何时候都可以有多个活动状态吗？
是的，每当 运行-to-completion 步骤完成时，可以有超过 1 个活动状态。实际上可以有一整棵活动状态树：
如你所说，复合状态的正交区域可以有活跃状态。复合状态也可以递归嵌套。这意味着如果嵌套状态处于活动状态，则其所有祖先也处于活动状态。因此，正交区域和嵌套复合状态的组合可以导致一整棵活动状态树。
UML Superstructure Specification, v2.4.1是这样解释的（第15.3.11章状态第564页）：
Active state configurations
In a hierarchical state machine more than
one state can be active at the same time. If the state machine is in a
simple state that is contained in a composite state, then all the
composite states that either directly or transitively contain the
simple state are also active. Furthermore, since the state machine as
a whole and some of the composite states in this hierarchy may be
orthogonal (i.e., containing regions), the current active “state” is
actually represented by a set of trees of states starting with the
top-most states of the root regions down to the innermost active
substate. We refer to such a state tree as a state configuration.
挑剔的可以例外：
如果状态机终止，当然根本没有活动状态，因此此时不可能有多个活动状态。
备注
UML 上层结构规范 v2.4.1 是 文档以检查您是否有此类问题。
我理解在复合状态下可以同时存在正交区域运行。 在 UML 状态机中，任何时候都可以有多个活动状态吗？
是的，每当 运行-to-completion 步骤完成时，可以有超过 1 个活动状态。实际上可以有一整棵活动状态树：
如你所说，复合状态的正交区域可以有活跃状态。复合状态也可以递归嵌套。这意味着如果嵌套状态处于活动状态，则其所有祖先也处于活动状态。因此，正交区域和嵌套复合状态的组合可以导致一整棵活动状态树。
UML Superstructure Specification, v2.4.1是这样解释的（第15.3.11章状态第564页）：
Active state configurations
In a hierarchical state machine more than one state can be active at the same time. If the state machine is in a simple state that is contained in a composite state, then all the composite states that either directly or transitively contain the simple state are also active. Furthermore, since the state machine as a whole and some of the composite states in this hierarchy may be orthogonal (i.e., containing regions), the current active “state” is actually represented by a set of trees of states starting with the top-most states of the root regions down to the innermost active substate. We refer to such a state tree as a state configuration.
挑剔的可以例外：
如果状态机终止，当然根本没有活动状态，因此此时不可能有多个活动状态。
备注
UML 上层结构规范 v2.4.1 是 文档以检查您是否有此类问题。