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1、Analyzing Workflows Outline ANALYSIS TECHNIQUES REACHABILITY ANALYSIS STRUCTURAL ANALYSIS Soundness Method with computer support Method without computer support PERFORMANCE ANALYSIS CAPACITY PLANNING Method to calculate capacity requirements Some basic queuing theory to take variability into account
2、ANALYSIS TECHNIQUES The process should contains no grave errors and be designed that the completion times of and capacity required for cases are kept as small as possible. By parallelizing tasks, completion times can usually be reduced.ANALYSIS TECHNIQUES It is useful to analyze it thoroughly prior
3、to its enactment. In doing so, we differentiate between the analysis of The qualitative aspects and mainly concern the logical correctness of the defined process. The quantitative aspects of workflows. mainly concern the performance of the defined process.ANALYSIS TECHNIQUES Begin with a simple tech
4、nique designed to illustrate all the states attainable in a case. The errors which can be made when drawing up the definition of a process. Based upon the structure of the underlying Petri net, we can decide whether a process definition is correct.ANALYSIS TECHNIQUES Concentrate upon the analysis of
5、 quantitative aspects. Using a number of examples to show how to improve the performance of existing processes. Study the subject of capacity planning.REACHABILITY ANALYSIS As learned in Chapter 2, a process can be defined in terms of a Petri net.REACHABILITY ANALYSIS (Cont.) One way to illustrate t
6、he behavior is to draw up a reachability graph.Non-deterministic choiceEnd state(a,b,c), where a: the number of tokens in the place claim, b: the number in under_consideration, and c: the number in ready.REACHABILITY ANALYSIS (Cont.) Reachability graph can embody the behavior of the process being mo
7、deled. We can compile a reachability graph, shows that Petri nets are an unambiguous and precise means of description. We used the network shown in Fig 4.4 to model the traffic lights at the junction of two one-way streets.A 7-tuple, shows the number of tokens in red1, green1, yellow1, red2, green2,
8、 yellow2 and x, respectively.REACHABILITY ANALYSIS (Cont.) the traffic lights operate safely: in every possible state at least one of the sets of lights is at red. it is also possible that the first set always changes to green, while the second set remains constantly at red. Can ensure that each set
9、 of lights changes to green in turn. Fig 4.6 shows how this can be modeled.REACHABILITY ANALYSIS (Cont.)REACHABILITY ANALYSIS (Cont.)REACHABILITY ANALYSIS (Cont.) It is easy to work out that the reachability graph associated with Fig 4.6 has a total of six states. Just as we can verify the correct o
10、peration of traffic lights using the reachability graph, we can use it to determine the correctness of a workflow. Business processes generally had a simple structure. By using databases and networks, information can be shared. Because different people can work on the same case at the same time, it
11、is no longer necessary for tasks to be performed sequentially.STRUCTURAL ANALYSISSTRUCTURAL ANALYSIS But the use of sequential, parallel, selective and iterative routing in the same process can make it very difficult to assess the correctness of the defined process.STRUCTURAL ANALYSIS (Cont.)STRUCTU
12、RAL ANALYSIS (Cont.)STRUCTURAL ANALYSIS (Cont.) Common errors during defining a process: Tasks without input and/or output conditions. Dead tasks: tasks which can never be carried out. Deadlock: the jamming of a case before the condition end is reached. Livelock: the trapping of a case in an endless
13、 cycle. Activities still take place after the condition end is reached. There remain tokens in the process definition after the case has been completed.STRUCTURAL ANALYSIS (Cont.) Tasks without input and/or output conditions. When a task has no input conditions, it is unclear when it may be performe
14、d. When a task has no output conditions, it does not contribute to the successful completion of a case and so it can be dropped.STRUCTURAL ANALYSIS (Cont.) Situation A in Fig 4.8 contains one task without input conditions (task4) and one without output conditions (task5).STRUCTURAL ANALYSIS (Cont.)
15、Dead tasks: tasks which can never be carried out. It is obvious that a process definition containing dead tasks is undesirable.STRUCTURAL ANALYSIS (Cont.) In situation B, task2 can never be performed; the same applies to task3 in situation D.STRUCTURAL ANALYSIS (Cont.) Deadlock: the jamming of a case before the condition end is reached. If task1 in situation B places a token in one of the two uppermost places, then the case will wait ad infinitum for task2. Only if task1 delivers a token directly to the place end will this deadlock be avoided.STRUC
