Examples of Workflows Workflow Typical Typical processing application task entity electronic-mail routing electronic-mail message mailers humans, loan processing form processing application software humans,application purchase-order processing form processing software,DBMSs Database System Concepts-6th Edition 26.12 @Silberschatz,Korth and Sudarshan
Database System Concepts - 6 26.12 ©Silberschatz, Korth and Sudarshan th Edition Examples of Workflows
Loan Processing Workflow loan application customer loan officer reject verification loan superior disbursement accept officer In the past,workflows were handled by creating and forwarding paper forms Computerized workflows aim to automate many of the tasks.But the humans still play role e.g.,in approving loans. Database System Concepts-6th Edition 26.13 @Silberschatz,Korth and Sudarshan
Database System Concepts - 6 26.13 ©Silberschatz, Korth and Sudarshan th Edition Loan Processing Workflow In the past, workflows were handled by creating and forwarding paper forms Computerized workflows aim to automate many of the tasks. But the humans still play role e.g., in approving loans
Transactional Workflows Must address following issues to computerize a workflow. Specification of workflows-detailing the tasks that must be carried out and defining the execution requirements. Execution of workflows-execute transactions specified in the workflow while also providing traditional database safeguards related to the correctness of computations,data integrity,and durability. E.g.:Loan application should not get lost even if system fails. Extend transaction concepts to the context of workflows. State of a workflow-consists of the collection of states of its constituent tasks,and the states(i.e.,values)of all variables in the execution plan. Database System Concepts-6th Edition 26.14 @Silberschatz,Korth and Sudarshan
Database System Concepts - 6 26.14 ©Silberschatz, Korth and Sudarshan th Edition Transactional Workflows Must address following issues to computerize a workflow. Specification of workflows - detailing the tasks that must be carried out and defining the execution requirements. Execution of workflows - execute transactions specified in the workflow while also providing traditional database safeguards related to the correctness of computations, data integrity, and durability. E.g.: Loan application should not get lost even if system fails. Extend transaction concepts to the context of workflows. State of a workflow - consists of the collection of states of its constituent tasks, and the states (i.e., values) of all variables in the execution plan
Workflow Specification Static specification of task coordination: Tasks and dependencies among them are defined before the execution of the workflow starts. Can establish preconditions for execution of each task:tasks are executed only when their preconditions are satisfied. Defined preconditions through dependencies: Execution states of other tasks. "task t;cannot start until task t has ended" Output values of other tasks. "task t;can start if task t;returns a value greater than 25" External variables,that are modified by external events. "task t;must be started within 24 hours of the completion of task t" Database System Concepts-6th Edition 26.15 @Silberschatz,Korth and Sudarshan
Database System Concepts - 6 26.15 ©Silberschatz, Korth and Sudarshan th Edition Workflow Specification Static specification of task coordination: Tasks and dependencies among them are defined before the execution of the workflow starts. Can establish preconditions for execution of each task: tasks are executed only when their preconditions are satisfied. Defined preconditions through dependencies: Execution states of other tasks. “task ti cannot start until task tj has ended” Output values of other tasks. “task ti can start if task tj returns a value greater than 25” External variables, that are modified by external events. “task ti must be started within 24 hours of the completion of task tj
Workflow Specification (Cont.) Dynamic task coordination E.g.,Electronic mail routing system in which the text to be schedule for a given mail message depends on the destination address and on which intermediate routers are functioning. Database System Concepts-6th Edition 26.16 @Silberschatz,Korth and Sudarshan
Database System Concepts - 6 26.16 ©Silberschatz, Korth and Sudarshan th Edition Workflow Specification (Cont.) Dynamic task coordination E.g., Electronic mail routing system in which the text to be schedule for a given mail message depends on the destination address and on which intermediate routers are functioning