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diff --git a/chapter/4/dist-langs.md b/chapter/4/dist-langs.md index 0059171..89eb496 100644 --- a/chapter/4/dist-langs.md +++ b/chapter/4/dist-langs.md @@ -183,6 +183,33 @@ It is worth noting that stack frame growth is still possible, but if the recursi #### Emerald +Emerald is a distributed programming language based around a unified object model. +Programs in Emerald consist of collections of Objects. +Critically, Emerald provides the programmer with a unified object model so as to abstract object location from the invocation of methods. +With that in mind, Emerald also provides the developer with the tools to designate explicitly the location of objects. + +Objects in Emerald resemble objects in other OOP languages such as Java. +Emerald objects can only be manipulated by methods that are exposed, and may contain internal state. +However, their are a few key differences between Emerald and Java Objects. +First, objects in Emerald may have an associated process which starts after initialization. +In Emerald, object processes are the basic unit of concurrency. +Additionally, an object may *not* have an associated process. +These objects more closely resemble traditional Java objects, and their code is executed when called by processes. +Second, processes may not touch internal state (members) of other objects. +Unlike Java, all internal state of Emerald objects must be accessed through method calls. +Third, objects in Emerald may contain a special *monitor* section which can contain methods and variables that are accessed atomically. +If multiple processes make simultaneous calls to a "monitored" method, the calls are effectively serialized. + +* single object model + * objects only manipulated by exposed methods + * can be moved + * identity, operations, process (optional) + * process, monitor, initially sections +* abstract types + * interfaces + * allow system upgrades, new implementations + * implementations can have different semantics for an interface + #### Argus #### Orleans |