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Re: Compendium of "synchronous" definitions

From: David Booth <dbooth@w3.org>
Date: Mon, 03 Mar 2003 13:47:39 -0500
Message-Id: <>
To: Francis McCabe <fgm@fla.fujitsu.com>
Cc: www-ws-arch@w3.org

And let's call your second definition "frank-2":

Definition frank-2
Synchronous activity
An activity involved in a synchronous rendezvous may assume that the 
rendezvous is complete for both sides if it 's side completes.

At 09:10 AM 3/3/2003 -0800, Francis McCabe wrote:
>   I would appreciate it if you could add mine to the long list:
>a straightforward definition of synchronous:
>A rendezvous of two activities is synchronous if they complete simultaneously.
>The language, if not the definition, comes from Communicating Sequential 
>One might try to sharpen this up by defining simultaneously in terms of 
>clocks etc. But that is not necessary; because an alternative view of this 
>definition is:
>An activity involved in a synchronous rendezvous may assume that the 
>rendezvous is complete for both sides if it 's side completes.
>On Thursday, February 27, 2003, at 04:58  PM, David Booth wrote:
>>Here are the proposed definitions of "synchronous" that I've collected 
>>from the list.  If I've missed any, it was only due to volume of messages 
>>I was trying to sort through -- not due to any desire to slight anyone -- 
>>so please accept my apology.  If that happened, and you do feel that 
>>(yet) another definition should be considered, please re-submit it to the 
>>list by reply message and give it a unique name as I've done with the 
>>others below, so that we can be clear when in referring to them.
>>          ==============================================
>>Definition dbooth-2
>>[This is my attempt at combining the main concepts I've seen in others.]
>>Synchronous interaction
>>An interaction is synchronous if the parties are involved in the 
>>interaction at the same time and the interaction carries an expectation 
>>of immediate processing.  A one-way interaction is synchronous if 
>>successful message delivery implies that the message either has been 
>>processed by the receiver or is actively being processed.  A round-trip 
>>or more complex interaction is synchronous if the initiator pauses some 
>>of its processing to wait for the interaction's constituent messages to 
>>be processed.  In a round-trip interaction, the request and response are 
>>often sent over the same communication channel.
>>Definition dbooth-1
>>Property of an interaction whose results are directly following the 
>>interaction. An interaction between an initiator and a respondent is 
>>synchronous if the initiator blocks some further processing while it 
>>waits for a corresponding action, response or acknowledgement from the 
>>Definition ugo-2c
>>Asynchronous: A request/response interaction is said to be asynchronous 
>>when the request and response are chronologically decoupled. In other 
>>words, the client agent does not have to "wait" for the response once it 
>>issues the initial request. The exact meaning of "not having to wait" 
>>depends on the characteristics of the client agent (including the 
>>transfer protocol it uses). Examples include receiving the response on a 
>>different thread, on a different socket, on a different end-point, by 
>>polling the server, etc.
>>Synchronous: The opposite of asynchronous.
>>Definition daveo-1
>>a programmatic flow of control on the sender effectively does nothing but 
>>wait for a response after sending it's request
>>Definition daveo-2
>>the request and response flow forwards and backwards over the same 
>>virtual connection between the sender and receiver.
>>Definition moberg-1
>>A web service response is said to be synchronous iff it is returned using 
>>the same network connection used in sending the request to which it is a 
>>response. (This implies that only one URL would be needed for 
>>request-response MEP when the response is synchronous and uses a transfer 
>>protocol that has URLs. It also implies that the request and response 
>>occur within the interval of time that the network connection exists. 
>>Also, there is overhead in setting up only one TCP connection when TCP is 
>>used, and since we are talking about IP _connections_ that will be almost 
>>always the case.)
>>A web service response is said to asynchronous iff it is returned using a 
>>network connection that is distinct from that used for sending the 
>>request to which it is a response. (Implications: Two URLs are needed to 
>>configure a request-response MEP when the response is ==>asynchronous. 
>>The response connection may occur while the request connection is still 
>>open or after it is closed. For TCP-based transfer protocols, two 
>>connection setups will be needed.)
>>Definition assaf-3
>>A transport is synchronous iff the request is returned using the same 
>>network connection.
>>Definition cutler-1
>>Synchronous: a request/response exchange that is correlated by virtue of 
>>a serialized, sequenced exchange of messages between requestor and 
>>respondant, typically over the same socket or stream.
>>Asynchronous: a request/response exchange that is not synchronous, 
>>typically relying on some mechanism such as Message-ID within the 
>>messages to correlate the request and response messages.
>>Definition ferris-1
>>synchronous message exchange (applies to oneway as well as 
>>request/response) requires that both sender and receiver, or initiator 
>>and respondant, processes are running/active at the same time as the 
>>exchange takes place. In the case of request/response, the exchange is 
>>synchronous if both sender and receiver remain in the running/active 
>>state for both the request and response.
>>asynchronous message exchange (also applies to oneway or request 
>>response) does not require, but does not preclude, that both sender and 
>>receiver, or initiator and respondant, processes are running/active at 
>>the same time as the exchange takes place. It typcally requires some form 
>>of mediation between the sender and receiver such as a message queue.
>>Definition mikec-1
>>(Taken from 
>>http://whatis.techtarget.com/definition/0,,sid9_gci213080,00.html ?)
>>In program-to-program communication, synchronous communication requires 
>>that each end of an exchange of communication respond in turn without 
>>initiating a new communication. A typical activity that might use a 
>>synchronous protocol would be a transmission of files from one point to 
>>another. As each transmission is received, a response is returned 
>>indicating success or the need to resend. Each successive transmission of 
>>data requires a response to the previous transmission before a new one 
>>can be initiated. Synchronous program communication is contrasted with 
>>asynchronous program communication.
>>Definition walden-1
>>Synchronous, then, places a constraint on a response such that the 
>>response must be received within a strictly or loosely defined time 
>>quantum (strict vs lax synchrony), or else the exchange fails.
>>Asynchronous differs in that no amount of elapsed time signals the 
>>failure of the exchange.
>>Definition assaf-1
>>An operation is synchronous if both service requester and service provider
>>engage will always engage in that operation at the same time.
>>Definition assaf-2
>>An interaction is synchronous if activities demarcated by that interaction
>>will always be performed at the same time.
>>David Booth
>>W3C Fellow / Hewlett-Packard
>>Telephone: +1.617.253.1273
>David Booth
>W3C Fellow / Hewlett-Packard
>Telephone: +1.617.253.1273
Received on Monday, 3 March 2003 13:47:53 GMT

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