Iterative Control Structures Research Articles

Unraveling Iterative Control Structures from Business Processes

Iterative control structures allow the repeated execution of tasks, activities or sub-processes according to the given conditions in a process model. Iterative control structures can significantly increase the risk of triggering temporal exceptions since activities within the scope of these control structures could be repeatedly executed until a predefined condition is met. In this paper, we propose two approaches to unravel iterative control structures from process models. The first approach unravels loops based on zero-one principle. The second approach unravels loops based on branching probabilities assigned at split gateways. The proposed methods can be used to unfold structured loops, nested loops and crossing loops. Since the unfolded model does not contain any iterative control structures, it can be used for further analysis by process designers during the modeling phase. The proposed methods are implemented based on workflow graphs, and therefore they are compatible with modeling languages such as Business Process Modelling Notation (BPMN). In the experiments, the execution behavior of unfolded process models is compared against the original models based on the concept of runs. Experimental results reveal that runs generated from the original models can be correctly executed in the unfolded BPMN models that do not contain any loops.

A semantics for Behavior Trees using CSP with specification commands

In this paper we give a formal definition of the requirements translation language Behavior Trees. This language has been used with success in industry to systematically translate large, complex, and often erroneous requirements documents into a structured model of the system. It contains a mixture of state-based manipulations, synchronisation, message passing, and parallel, conditional, and iterative control structures. The formal semantics of a Behavior Tree is given via a translation to a version of Hoare’s process algebra CSP, extended with state-based constructs such as guards and updates, and a message passing facility similar to that used in publish/subscribe protocols. We first provide the extension of CSP and its operational semantics, which preserves the meaning of the original CSP operators, and then the Behavior Tree notation and its translation into the extended version of CSP.

Toward integrating imperative and logic programming paradigms

This paper presents an integration of imperative and logic programming, implemented on a PROLOG interpreter. The idea is to exploit the interpreter's execution model to support a procedural style of coding, and to imcorporate the notion of state by means of the use of the internal database. Both the coding style and some experimental structured-like programming constructs are discussed. The proposed integration provides hints to achieve an extensible language (i. e. iterative control structures that may be useful when tail recursion optimization is not possible) and also benefits in learning the equivalence between its declarative and operational semantics.

A General, Verifiable Iterative Control Structure

A general iterative control structure with multiple exits and multiple retums to the beginning of the loop is described. The conditions causing these exits or returns must be declared and defined in a prologue to the loop in a manner which is similar to the declaration of variables at the beginning of a block. Also, actions prior to an exit or a return may be specified in an epilogue of the loop. The semantics of the structure are described informally and then formally by means of a Hoare type verification rule. Attributes of the structure and examples of its usage are given in the latter part of the paper.