idef3_kbsi_report (1013870), страница 32
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The purpose ofacquiring a description is to represent how the system actually works, rather than how thedomain expert thinks the system works (or how the domain expert thinks the systemshould work). Therefore, the analyst needs to correlate facts captured in the interviewprocess with first-hand observations of the process. The analyst also must avoidcompleting the description with his or her own (often preconceived) knowledge abouthow the system ought to work.
Thus, it is important that both the analyst and the domainexpert understand that descriptions are often partial in nature and curb their desire tomake them ideally complete.Analyze Description for Data IdentificationOnce the interview is over, the analyst needs to carefully study the recorded notes andobservations. This analysis identifies the objects, activities, facts, and constraints thatoccur in the description. This step is a list-making process.When describing processes, individuals often focus on the key objects in the processand their roles in the process before actually describing the events or activities that occurduring the process.
The following is a list of objects that were identified in thedescription.149MaterialPurchasing DepartmentContractOrderPotential SupplierBidCurrent SupplierRequesterPurchase RequestAccount ManagerBackupProject AccountPurchase OrderChosen SupplierIt is important that the analyst explicitly record the list of objects in the IDEF3 objectpool for the following reasons.1.The analyst may omit some of the objects at a later stage in thedescription capture process.2.This list of objects from the first analysis often contains the primaryobjects in the process. Primary objects are those objects importantenough to warrant the creation of an Object Schematic.After identifying objects, the interview notes are examined to determine theactivities/processes that occur in material ordering.
The important activities arecandidates to be represented as UOBs (activities, actions, or processes) in the description.However, at this stage of development, the sequence of the activities is not important.The primary goal is to list the candidate UOBs (as shown in the following list). Thesecandidate UOBs would be listed in the IDEF3 UOB pool. It is likely that the list ofUOBs is incomplete; however, this is not a matter of much concern at this stage. Thefirst description yields the following UOBs.1.Request material.2.Identify potential suppliers.3.Identify current supplier.4.Request bids.5.Evaluate bids.6.Order requested material.The second description yields four additional UOBs.7.Prepare purchase request.1508.Obtain account manager’s approval.9.Obtain authorization signature.10. Submit signed purchase request.The final step in the interview analysis involves identifying and listing facts andidentifying the constraints relevant to the processes described by the domain expert.Facts are assertions made about the objects.
Constraints are distinguished conditions thatare known to hold between the objects within a process, or between the processesthemselves. To identify the occurrence of constraints, look for negative terms such asnot, never, or no (as well as quantifiers like every, all, and only) in the recorded verbaldescription. The list of facts and constraints is likely to be incomplete early in thedevelopment. Further interviews or conversations with the domain expert will aid inmaking the lists of facts and constraints more complete. An initial list might include thefollowing:1.There are 7 current suppliers.2.No one besides the designated account manager or his or her backupis allowed to approve purchases against their assigned account.3.The requester cannot be the same individual as the one who approvesor authorizes the request.Formulate Process SchematicsOnce the initial task of identifying objects, activities, facts, and constraints nearscompletion, the IDEF3 Process Schematic (or a set of schematics) is ready to beformulated.
The observations recorded in the interviews are used as the basis fordeveloping the Process Schematics. Candidate UOBs listed in the data analysis phasewill be used in this step to construct the UOBs. Facts and constraints identified from theinterview notes will be used to construct UOB elaborations. Developing a ProcessSchematic occurs in two major stages, (1) constructing UOBs in correct sequence and (2)developing UOB elaborations.151Layout Initial Process SchematicThe process of identifying the UOBs and specifying the precedence between themoccurs in several steps.Step 1.
Identify the left-most UOB in the process description, the UOBRequest Material.Step 2. Identify the next UOB. In this example, two UOBs are possible:Identify Current Supplier or Identify Potential Suppliers.The second step implies a split in the process flow, indicating the need to use a fanout junction to represent the diverging flow. The analyst must determine the junctiontype that initiates the split. In this example, the Purchasing Department can perform onlyone of the two alternative activities; therefore, an XOR junction is used. The analyst mayfind it useful at this stage to create the partial schematic shown in Figure 5-1.Identifypotentialsuppliers2Requestmaterial1XJ1Identifycurrentsupplier3Figure 5-1First Steps in Process Schematic DevelopmentIf a split in the process had not occurred, the development would have continued withthe sequential drawing of UOB boxes until a split did occur.
After a split, each processpath is developed separately. These process paths may or may not converge within thecontext of the given description. The order in which the process paths are developed is amatter of preference.Step 3. The next step is to develop the path that begins with UOB 2. Thispath continues sequentially with the UOBs Request Bids, Evaluate Bids,and Order Requested Material. These UOBs result in the partialschematic shown in Figure 5-2.152Identifypotentialsuppliers2Requestmaterial1RequestbidsEvaluatebids45XJ1Identifycontractsupplier3Figure 5-2Schematic with the First Path CompleteStep 4. The fourth step is to complete the remaining path in Figure 5-2,resulting in the Process Schematic shown in Figure 5-3. Note that theUOBs retain the numbers assigned as they were placed in the activities list.The second path also results in the placement of an order for the requestedmaterial.
This implies a convergence in the process flow and the need fora fan-in junction to represent the convergence. The analyst mustdetermine the appropriate junction type for the convergence. In thisexample, only one of the two paths was possible, as indicated by the fanout XOR that precedes each path. Therefore, a fan-in XOR junction isused.153Orderrequestedmaterial6154Figure 5-3Schematic Near CompletionIdentifypotentialsuppliers2Requestmaterial1Requestbids4Evaluatebids5XXJ1J2Identifycurrentsupplier3Orderrequestedmaterial6Step 5. When the schematic illustrated in Figure 5-3 is finished, there arestill four activities in the list of potential UOBs. UOBs 7 through 10 arethe domain expert’s description of the Request Material UOB.
Someanalysts find it easier to begin schematic development at a more detailedlevel and later create decompositions to simplify the schematic. Othersfind it more convenient to begin schematic development at a higher levelof abstraction and begin by only classifying the activities and viewpointsthat they might want to investigate later through the creation ofdecompositions. Developing decompositions helps to keep the schematicsimple and also affords the analyst additional opportunity to collect andorganize alternative descriptions of how the Request Material activity isperformed. This choice yields the schematic displayed in Figure 5-4.Identifypotentialsuppliers2RequestmaterialRequestbids45X1EvaluatebidsXJ1J2Identifycurrentsupplier3PreparePurchaseRequest1.1.7Obtain AccountManager'sapproval1.1.8ObtainauthorizationsignatureSubmit signedPurchaseRequest1.1.91.1.10Figure 5-4Complete Process Description Schematic Before First Review155Orderrequestedmaterial6Develop ElaborationsAfter the initial Process Schematic has been completed, elaborations must be added toeach UOB as shown in Figures 5-5 through 5-9.
In the initial attempt, these may besomewhat incomplete. One reason for this may be that the primary focus of the analyst inthe first interview is on the objects and activities. This is particularly true in thedevelopment of either a description for a process with which the analyst was unfamiliaror a description of a large, complex process.When the analyst is familiar with the process type, more information can be obtainedabout the particular process in the first interview. The analyst’s questions would reflectthis familiarity and in the first interview the analyst could determine how the processdiffers from other systems of this type.
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