Adaptation is an important concept for Web processes. The author provides an overview of adaptation with respect to control theory and how it is applied to other contexts. Specifically the author focuses on open loop and closed loop adaptation. Then the cahpter discusses the current Web process standard WS-BPEL supports open loop adaptation. Finally, the author discusses an academic research framework METEOR-S, which supports closed loop adaptation.
Time features any aspect of human life, being associated or associable with any fact or information or event. The need for supporting temporal information, as well as storing, reasoning about, and representing data and facts, has been recognized for a long time (Snodgrass & Ahn, 1985), showing that a proper management of temporal information is required. The literature presents an analysis of the current status and sketches about future trends on storing (Jensen & Snodgrass, 1999, Khatri et al., 2004), representing and reasoning (Chittaro & Montanari, 2000) on temporal information: other papers consider these trends in several application domains, e.g. in medicine (Adlassnig et al., 2006, Combi & Pozzi, 2006b).
Time is thus relevant for any human activity, either if managed in a “traditional” way or with the support of ICT (Information and Communication Technology) tools. Workflow Management Systems - WfMS – (Aalst & van Hee, 2004, Grefen et al., 1999, Weske, 2007) can help in managing activities and/or business processes, and can be even more helpful if such systems can properly manage time and related temporal dimensions (i.e., temporalities). As an example, changes in the managed information, in the organization, in the process model, as well as deadlines, constraints on the activation or completion of a task or of the entire process, temporal synchronization of tasks can be easily defined, monitored, and detected by a suitable WfMS (Marjanovic & Orlowska, 1999a, Marjanovic & Orlowska, 1999b).
Since most of the information managed by a WfMS is stored by a database management system (DBMS), it can be easily observed that a suitable management of temporalities by the DBMS itself, which could result in a temporal DBMS (TDBMS), could be helpful. Unfortunately, and to the best of our knowledge, very few TDBMSs are available: despite this, we shall consider throughout the paper that some temporalities can be managed at the DBMS level: as an example, we shall assume that the valid time dimension, which is one of the relevant elements in managing temporalities, is available and manageable by the DBMS.
The chapter is organized as follows. The first section is entitled Temporalities in Workflow Models and it considers the main models and the related temporalities used in a workflow system: the process model, describing the single atomic work units and their coordination; the information model, describing all the information of the process instances (i.e., cases) by the workflow system; the organizational model, describing the agents (i.e., participants, which can be human or not, of an organization), and the structure of the organization where process instances will be executed.
The second section is entitled Temporalities in Expected Exceptions and it considers the abnormal events, also known as exceptions, which may occur during the execution of process instances. The section focuses on expected exceptions, i.e. those exceptions which must be considered at process design time, may occur at any time during the execution of the process, may deviate the “normal” flow of execution, and include a not negligible semantics.
The third section is entitled Temporal Scheduling and it considers the scheduler of a workflow management system, its policies for assigning tasks to agents and for fulfilling the defined temporal constraints. The section also includes the description of one possible algorithm for a temporal scheduler of a WfMS.
The fourth section is entitled Temporal Architectures for WfMSs and it considers both the general architecture of a WfMS and the changes that can be applied to such architecture, enriching it to suitably managing temporalities. The section discusses the pros and cons of three different architectures, depending on the availability of a full-fledged temporal database management system or not.
Finally, the last section entitled Conclusions provides an overview of the chapter and sketches out some possible research topics in the area.