Have you heard the one about how to drive BPM people crazy?\u00a0<\/p>\n
Ask them the question that drives CEP people crazy!<\/p>\n
Last fall, at the RuleML conference in Orlando, was the first time I heard a consensus that a standard ontology of events and processes was sorely needed.\u00a0 I’ve had a number of discussions with others on this over the interim until today’s posts by Paul Vincent, summing up<\/a> an OMG meeting in Washington, DC, and Sandy Kelmsley’s comments<\/a> on a survey of 590 business process modeling notation users.\u00a0\u00a0<\/p>\n For me, the Great BPMN Debate<\/a> boils down to two things:<\/p>\n I like BPMN.\u00a0 I wound not want to sacrifice much.\u00a0 But as a customer, I would think interchange is critical.\u00a0 Regrettably, Mr. Silver points out some problems serializing to XPDL and other issues with vendor coverage. \u00a0We are a ways from effective standards for rules or BPM, it appears.\u00a0 By effective, I mean standards supported by vendors that actually facilitate interchange between vendors.<\/p>\n One problem with all these standards, and even the web ontology language (OWL), is that they lack a common ontology.\u00a0 That is, they are syntax lacking shared semantics.\u00a0 Until they share some semantics, integrating or interchanging between them will remain imprecise , unproductive, and overly technical.\u00a0 Everything but technical rules and models (e.g., vocabulary) will remain locked in.<\/p>\n Just reading Mr. Silvers post, you find start and end events, throwing and catching events, intermediate events, exclusive events, timer, message, error and terminate events.\u00a0 And there are more.\u00a0 Too many, BPMN users agree, according to the survey cited above.<\/p>\n How many different kinds of events are there (or should there be)?\u00a0 For now, I’m going with 2.<\/p>\n Ask any complex event processing (CEP) vendor!\u00a0 It will drive them crazy or you will get a long-winded answer. Or, like me, they might say that it is something that happens or occurs.<\/p>\n At first, most people think of events as occurring at a point in time. \u00a0After some discussion, however, most people agree that events are things that we view as occurring instantaneously, even if they take a day, such as last year’s 4th<\/sup> of July picnic, which we might also call an occasion.\u00a0 Events, like the lights going on or a starting gun firing, might indeed be effectively instantaneous, in which case we would not call them occasions.<\/p>\n There is more to the difference between occasions and instantaneous events, however.<\/p>\n Is an event an occurrence or something that occurs?\u00a0 The difference is \u00a0similar to the difference between days, such as Friday versus March 14, 2008.\u00a0 One is what BPMN would call an event type and the other is an event.\u00a0 Well, not exactly, I doubt BPM folks would be happy thinking of a day as an event.\u00a0 Perhaps they would prefer that the start or end of each Friday was a type of an event and that the start of this Friday (i.e., today) was a specific instance of the “start of a Friday” event type.<\/p>\n For those who read about understanding time<\/a>, the difference between event types and events is similar to the difference between specific and recurring times.\u00a0 The semantics of introducing different types for starting and ending events is troublesome, however.\u00a0 Especially if how they are different is not specified semantically.<\/p>\n Generally, for all X, I do not like X “types”. When we talk with friends other than colleagues, using the word “type” confuses them.\u00a0 When talking to non-technical folks, instead of saying “event types”, why not just say “events”?\u00a0 Come to think about it, why don’t we talk about process types?\u00a0 (I’m sure someone thinks BPMN needs them!)<\/p>\n Most people would agree that things happen.\u00a0 Most people would also agree that events happen.\u00a0 The word “occur” is interchangeable with “happen” here.\u00a0 Do you agree that processes, like events, also occur or happen?<\/p>\n If specific instances of events are occurrences of “event types”, what is a specific instance of a process?<\/p>\n If celebrating the 4th<\/sup> of July is a process and last year’s 4th<\/sup> of July picnic was an event, could an instance of a process be an event?\u00a0 Or, is every instance of an event type an occurrence of a process?<\/p>\n Yes and No.\u00a0 Yes, but, for all X, I do not like X “instances”, for the same reason that I do not like X “types”.\u00a0 In other words, yes, occurrences of processes can be viewed as events.<\/p>\n But no, some events are not processes.\u00a0 For example, the start of a process can be viewed as an event, as BPMN views it, but the start of a process is not necessarily a process in and of itself.\u00a0 We could recurse into philosophy on this one, I guess, but at some level, the beginning of an explosion stops being interesting from a process perspective.<\/p>\n Avoiding philosophy as much as possible while remaining semantic:<\/p>\n Ontologically, a process is disjoint from an instantaneous event but both are events.<\/p>\n\n
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BPMN is overwhelmed by events<\/strong><\/h3>\n
What is an event?<\/strong><\/h3>\n
What occurs or happens?<\/strong><\/h3>\n
When is a process not an event?<\/strong><\/h3>\n
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