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HEADING User gateways are introduced to express human choices. The specificationof human-executed choices in BPMN is an open issue currentlyunder discussion in the BP analyst community 1 . Social applicationscorroborate the need of a better way to explicitly model humandecisions, which can be achieved simply by distinguishing user gateways,which entail a user’s decision; and automatic/service gateways,which entail a decision taken according to a rule (this is thestandard semantics for BPMN gateways) or performed by a service.Notice that the visibility of process status and the level of social participationdo not require an ad hoc notation because they can be inferred from theBPMN diagram, by looking at the flow, task, and event definitions.While most social interaction may be described with standard message flowswithin the community pool or between the community and the enterprisepool, a simplified notation may be convenient in several cases. Table 4 proposesa set of annotations describing social interactions at the task level.These annotations are a shortcut for social activities: they express thebroadcasting of messages/contents from a task to the entire social network(or a subset thereof), the posting of messages/contents to one member of thenetwork, the invitation of people from the social network to perform a specifictask, the invitation to comment or vote on a task or on its outcomes, thelogin of users in the BPM system using credentials from a social network,and the search for user’s skills or reputation within a social network (e.g., forchecking recommendations before assigning tasks to users). These annotationsgreatly simplify the expression of typical social activities, because theyavoid the visual clutter due to the introduction in the BPMN diagram of thecommunity pool and to the plethora of messages flowing into/from it.Finally, Table 5 shows the event types needed for supporting case advancementtriggered by social interactions. A generic social event conceptrepresents any kind of occurrence within the social network; this can bespecialized to express more detailed event types like: the addition of a newuser to the community, the establishment of a new social relationships, thenotification of acceptance/rejection of a social request (e.g., for friendship,invitation to groups or applications), and so on.1 The interested reader may refer to the online discussions proposed by Keith Swenson,Anatoly Belychook, Bruce Silver, and our own blog respectively at:http://social-biz.org/2009/04/06/representing-choice-in-a-process-diagram/,http://mainthing.ru/item/361/,http://www.brsilver.com/wordpress/2009/04/10/keiths-choice/, andhttp://marcobrambi.blogspot.com/2011/01/user-gateways-in-bpmn.html .10