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3.2.2. Rules in business process models > 3.2.2. Rules in business process mode... - Pg. 61

40 CHAPTER 3 A brief history of rules UML allows much the same data constraints to be modeled as Entity-Relationship Modeling. In addition, 1. like ORM but unlike Entity-Relationship Modeling, object class models provide for frequency constraints (see Section 3.2.1.2); 2. again, like ORM but unlike Entity-Relationship Modeling, n-ary associations can be specified, involving more than two object classes; 3. any constraints not formally provided by the notation can be stated in notes placed on the object class model diagram. It also provides an Object Constraint Language (OCL). This, however, is a declarative programming language rather than a language in which to document rules for stakeholder consumption. For example, 1. To ensure that the number of passengers specified in a flight booking request is nine or less requires the following statement: context FlightBookingRequest inv: self.numberOfPassengers <¼ 9 while to ensure that no more than 9 passenger names are listed in a flight booking confirmation requires the following statement: 2. To express the constraint that only a Personal Customer who has specified a first given name can specify a second given name requires the following statement: context FlightBookingRequest inv: {self.secondGivenName->isEmpty() or self.firstGivenName->notEmpty()}. context FlightBookingConfirmation inv: self.passenger->size() <¼ 9. 3.2.2 Rules in business process models Various business process modeling notations have been used over the years, ranging from process flow- charts through data flow diagrams to current notations such as BPMN. 7 Among the situations that may be represented in business process models are 1. a process sequence, a set of processes in which each process other than the first must not start until the preceding process is completed: for example, a loan approval cannot occur until a credit check is completed and funds may not be disbursed until the loan approval is completed; 2. a decision point from which flow two or more sequences of processes depending on some logical condition, or, in BPMN terms, an exclusive gateway which allows only one of a set of following processes to proceed based on some condition established in the preceding process: for example, an airline passenger already in possession of a boarding pass proceeds either to a bag drop desk (if he or she has bags to be checked in) or directly to security screening (if he or she only has carry-on bags); 3. a synchronizing gateway which allows the following process to proceed only after all preceding processes are completed: for example, a pasta meal can be served only after both the pasta and the sauce have been cooked; 7 (Object Management Group) (www.bpmn.org), (Silver, 2009).