Transaction Flow
What is Transaction flow?
Ø A unit of work seen from a system users point of view is known as transaction
Ø It contains the sequence of operations, some of which are performed by a system, persons or devices that are outside of the system
Ø Transactions begin with birth, i.e. they are created as a result of some external act
Ø At the conclusion of the transactions processing, the transaction is no longer in the system
Example:Following are the steps included in a transaction for an online information retrieval system
v Accept input(tentative birth)
v Validate input(birth)
v Transmit acknowledgment to requester
v Do input processing
v Search file
v Request directions from user
v Accept input
v Validate input
v Process request
v Update File
v Transmit output
v Record transaction in log and clean up(death)
Usage:
v Online systems are most complicated system. In this, the transaction flows are indispensable for specifying requirements.
v Air traffic control or airline reservation systems are the big systems. It has thousands of different transaction flows
v The flows are represented by relatively simple flow graphs, many of which have a single straight-through path
v Loops are infrequent compared to control flow graphs
v The most common loop is used to request a retry after 'user input' errors
Example: An ATM system allows the user to try, say three times, and will take the card away the fourth time.
Implementation:
v The implementation of a transaction flow is generally implicit in the systems control structure and the database it uses
v A transaction flow is a representation of a path taken by a transaction through a succession of processing modules. Think of each transaction as represented by a token that passes from one routine to routine as it progresses through flow
v Transaction flow graph is a diagrammatic representation of what happens to the tokens
v These tokens are, in general not manipulated by the control structure of the program
Perspective:
v Transaction flow testing is the ultimate black box testing as all we know is that there is a transaction and the system will do predictable actions to the transaction
v Transaction flow graphs are kind of data flow graphs as we look at the various data objects and the operation performed on them
v We should note that the decision nodes of transaction flow graph can be complicated in their own rights
v Our transaction flow model should be a simplified version of those decisions
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