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This Concept Map, created with IHMC CmapTools, has information related to: Remote procedure and events, heterogenous: when event notifications are used as a means of communication between distributed objects, components in a distributed system that were not designed to interoperate can be made to work together, all that is required is that event gathering objects publish types of events they offer and other objects subscribe to these events and provide an interface for receiving notifications asynchronous: notifications are sent asynchonously by event generating objects to all the objects that have subscribed to them to prevent publishers needing to synchronize with subscribers - publishers and subscribers need to be decoupled, network places are used include Events and notifications: notifications of events are essentially asynchronous and determined by their receivers, Case study: Sun RPC which was designed for client server communication in Sun NFS network file system has inteface definition language: the Sun XDR language, which was orginally designed for specifying external data representations, was extended to become an interface definition language, Sun RPC is rather primitive: 1 most languages allow interface names to be specified, Sun RPC does not 2 a procedure definition specifies a procedure signature and a procedure number 3 only a single input parameter is allowed 4 the ouput parameters of a procedure are returned via a single result 5 the procedure signature consists of the result type, event types: an event source can generate events of one or more different types. each event has attributes that specify info about that event such as the name or identifier of the object generated has roles for observers: tasks of processing notifications, forwarding: carries out all work of sending notifications to subscribers on behalfof one or more objects of interest, filtering of notifications: may be applied by an observer so as to reduce the number of notifications received according to smoe predicate on the contents of each notification, patterns of events: when an object subscribes to events at an object of interest, they can specify patterns of events that they are intersted in, notification mailboxes: an observer may take on this job to hold notifications of subscibers only to pass them on when the subscriber is ready to receive them, heterogenous: when event notifications are used as a means of communication between distributed objects, components in a distributed system that were not designed to interoperate can be made to work together, all that is required is that event gathering objects publish types of events they offer and other objects subscribe to these events and provide an interface for receiving notifications asynchronous: notifications are sent asynchonously by event generating objects to all the objects that have subscribed to them to prevent publishers needing to synchronize with subscribers - publishers and subscribers need to be decoupled, network places are used include case study: Jini distributed event specification: main objects involved are- event generators: an object that allows other objects to subscibe to its events and generates notifications, remote event listeners: object that receives notifications, remote events: object that is passed by value to remote event listeners, third party agents: may be interposed between an object of interest and a subscriber, the participants in distributed event notification: roles of the participating objects- the object of interest: object being invoked and experiences changes of state, event: occurs at completion of a execution, notification: object contains info about an event, subscriber: object that has subscribed to some type of events in another object, observer objects: to decouple an object of interest from its subscribers, publisher: object that declares it will generate notifications of events ???? event types: an event source can generate events of one or more different types. each event has attributes that specify info about that event such as the name or identifier of the object generated, Case study: Sun RPC which was designed for client server communication in Sun NFS network file system contains binding: Sun RPC runs a local binding service called the port mapper at a well known port number on each computer, each instance of a port mapper records the program number, version number and port number in use by each service running locally, event types: an event source can generate events of one or more different types. each event has attributes that specify info about that event such as the name or identifier of the object generated with delivery semantics: different delivery guarantees that provide for notifications, which depend on requirements of applications, third party agents: can be set up by an event generator or by a subscriber, they are equivalent of observers with simple dealing room system: information arrives in a dealing room from several different external sources in the form of updates to some or all of the instance variables of the objects representing the stocks and is collected by processes we call information providers, a dealing room system could be modelled by processes with two different tasks: 1 an info provider process continuously receives new trading info from a single external source and applies it to the appropriate stock objects, each of the udates to a stock object is regarded as an event 2 a dealer process creates an object to represent each named stock that the user asks to have displayed. this local object subscribes to the object representing that stock at the relevent info provider, Remote procedure call: similar to a remote method invocation in that a client program calls a procedure in another program running in a server process contains Case study: Sun RPC which was designed for client server communication in Sun NFS network file system, heterogenous: when event notifications are used as a means of communication between distributed objects, components in a distributed system that were not designed to interoperate can be made to work together, all that is required is that event gathering objects publish types of events they offer and other objects subscribe to these events and provide an interface for receiving notifications asynchronous: notifications are sent asynchonously by event generating objects to all the objects that have subscribed to them to prevent publishers needing to synchronize with subscribers - publishers and subscribers need to be decoupled, network places are used include the participants in distributed event notification: roles of the participating objects- the object of interest: object being invoked and experiences changes of state, event: occurs at completion of a execution, notification: object contains info about an event, subscriber: object that has subscribed to some type of events in another object, observer objects: to decouple an object of interest from its subscribers, publisher: object that declares it will generate notifications of events, Events and notifications: notifications of events are essentially asynchronous and determined by their receivers has third party agents: can be set up by an event generator or by a subscriber, they are equivalent of observers