Use Show We distinguish between two processing types for a Web service:
Synchronous Communication Synchronous communication can be implemented in function calls that require the immediate return of data to the sender system. The client sends a message to the server and waits until he or she receives a reply from the latter. Synchronous communication uses a single function call. Prerequisite for this is that at the time the call is made, the receiving system is also active and can accept the call and further process it. A disadvantage of synchronous communication is that it must be ensured that both systems are active and can be addressed. If they are not, this can lead to disruption of processes. In particular, problems can arise if the receiving system is not available for long periods of time due to maintenance, for example, for a system upgrade. A synchronous Web service uses the Request Response Message Exchange Pattern (MEP). The client sends off a request and waits for an answer from the provider. The client is blocked during this. The client cannot start any more calls. A transport guarantee is not provided with synchronous Web services since the client receives an indirect confirmation, through the response, that the call was processed successfully. The transactions, too, are not provided with synchronous Web services. This means that each individual call is sent directly to the provider, and it is converted there. Calls are not collected first and then submitted together. All following calls are blocked. For this reason, there is no guarantee for call sequence. Features of a Synchronous Web Service :
Asynchronous Communication For asynchronous communication, the receiving system does not have to be available at the time a function call is dispatched from the sender system. The receiving system can receive and process the call at a later time. If a system is, for example, unavailable for a long period of time because of an upgrade, it can still process the data that has been sent in the interim at a later time, and processes in the sending system remain unharmed. Function calls are put in the sender system outbound queue. from where the call is repeated at regular intervals until it can be processed by the receiving system. If a purchase order is sent to a vendor system, the sender system has no influence over the availability of the receiver system. If the receiving system is not available, the purchase order can be sent repeatedly until the vendor system is available again. Asynchronous communication is not to be used for processes that require an immediate response to the sender system. With asynchronous Web services, on the other hand, the client continues to work after a service call has been submitted - without being blocked while waiting for the answer. There is no answer with asynchronous Web service since the OneWay Message Exchange Pattern is used. In this way, the client requires the security that his or her calls arrive on the provider side. Therefore, the transport guarantee is offered for asynchronous Web services. Moreover, calls on the client-side are performed transactionally. This means that all calls for a transaction are collected until the transaction is complete. This prevents parts of a transaction from being retained (data persistence) already on the provider side although the remainder could no longer be transmitted. Since each call is sent separately to the provider, it can happen that message b arrives before message a . To balance this out, the Web Services Reliable Messaging feature is implemented. A sequence covers all calls of a logical unit of work (LUW) and assigns numbers to them. These are evaluated at the provider-side. In this way it is ensured that messages in a sequence are processed in the right sequence and that problems do not occur because one action requires another one that has not yet taken place. Features of an Asynchronous Web Service:
How are messages transmitted?Encoded messages are sent through a channel, or a sensory route on which a message travels, to the receiver for decoding. While communication can be sent and received using any sensory route (sight, smell, touch, taste, or sound), most communication occurs through visual (sight) and/or auditory (sound) channels.
How is a message transmitted to a receiver?In this process, the sender forms a message and encodes it into words or symbols. The encoded message is transmitted to the receiver through a channel or medium. The receiver senses the incoming message and decodes it for understanding the message.
What transmits the message in communication?Communication starts with information being sent from one to another. The person who transmits the message is called the sender. The person on the other side of the channel and receiving the message is called the receiver.
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