Command-query separation distinguishes commands that change state from queries that return observations without changing that state. It permits repeated inspection without further updates, but clients may need a protocol connecting updates and subsequent observations. Combining a command and its resulting observation into one object method can be convenient for transformation object interfaces. Neither organization alone guarantees thread safety.
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Command-Query Separation (CQS) is a programming principle that states that a method should either be a command that performs an action or a query that returns data, but not both. This principle helps to maintain a clear distinction between actions that change the state of a system and those that retrieve information about the system's state. ### Key Aspects of CQS: 1. **Commands**: These are methods that perform operations that modify the state of an object or system.