Path expression
In query languages, path expressions identify an object by describing how to navigate to it
in some graph of objects. For example, the path expression p.Manager.Home.City might refer the city of residence of someone's manager.
Path expressions have been extended to support regular expression-like flexibility.
XPath is an example of a path expression language.
In concurrency control, path expressions are a mechanism for expressing permitted sequences of execution. For example, a path expression like ", write" might specify that either multiple simultaneous executions of read or a single execution of write but not both are allowed at any point in time.
