Abstract
A celebrated contribution of Bellantoni and Cook was a function algebra to capture FPTIME. This algebra uses recursion on notation. Later, Oitavem showed that including primitive recursion, an algebra is obtained that captures FPSPACE. The main results of this article concern variants of the later algebra. First, we show that iteration can replace primitive recursion. Then, we consider the results of imposing a monotonicity constraint on the primitive recursion or iteration. We find that in the case of iteration, the power of the algebra shrinks to FPTIME. More interestingly, with primitive recursion, we obtain a new implicit characterization of the polynomial hierarchy (FPH). The idea to consider these monotonicity constraints arose from the results on write-once tapes for Turing machines.We review this background and also note a new machine characterization of delta(P)(2), that similarly to our function algebras, arises by combining monotonicity constraints with a known characterization of PSPACE.

Abstract
The IEEE 802.15.4 standard provides a flexible communication approach for LR-WPAN networks. When active, the beacon-enabled mode allows real-time communication by adopting a GTS (Guaranteed Time Slot) mechanism. However, this mechanism supports only up to seven real-time communicating devices. Motivated by this problem, this paper proposes the use of a dynamic GTS scheduling approach based on the (m,k)-firm task model, to deal with the GTS starvation problem. The proposed approach ensures that, for each admitted message stream S-i at least m messages will be transmitted within each window of k consecutive deadlines. The effectiveness of the proposed scheduling approach is demonstrated by a set of simulation and experimental results. The proposed approach is fully compatible with the IEEE 802.15.4 standard.

Abstract
Currently, in order to remain competitive companies are adopting customer centered strategies and consequently customer relationship management is gaining increasing importance. In this context, customer retention deserves particular attention. This paper proposes a model for partial churn detection in the retail grocery sector that includes as a predictor the similarity of the products' first purchase sequence with churner and non-churner sequences. The sequence of first purchase events is modeled using Markov for discrimination. Two classification techniques are used in the empirical study: logistic regression and random forests. A real sample of approximately 95,000 new customers is analyzed taken from the data warehouse of a European retailing company. The empirical results reveal the relevance of the inclusion of a products' sequence likelihood in partial churn prediction models, as well as the supremacy of logistic regression when compared with random forests.

Abstract
This study deals with industrial processes that produce soft drink bottles in different flavours and sizes, carried out in two synchronised production stages: liquid preparation and bottling. Four single-stage formulations are proposed to solve the synchronised two-stage lot sizing and scheduling problem in soft drink production synchronising the first stage's syrup lots in tanks with the second stage's soft drink lots on bottling lines. The first two formulations are variants of the General Lot Sizing and Scheduling Problem (GLSP) with sequence-dependent setup times and costs, while the other two are based on the Asymmetric Travelling Salesman Problem (ATSP) with different subtour elimination constraints. All models are computationally tested and compared to the original two-stage formulation introduced in Ferreira et al. (2009), using data based on a real-world bottling plant. The results show not only the superiority of the single-stage models if compared to the two-stage formulation, but also the much faster solution times of the ATSP-based models.

Abstract
We are proud to introduce this special issue of LIPIcs - Leibniz International Proceedings in Informatics, dedicated to the technical communications accepted for the 28th International Conference on Logic Programming (ICLP). © Agostino Dovier and Vítor Santos Costa.

Abstract
The purpose of the present study was to examine the reliability, factorial validity and measurement invariance (across gender, age and physical activity participation) of a Portuguese version of the Rosenberg Self-Esteem Scale (RSES). The sample consisted of 1,763 Portuguese youngsters (731 male and 1,032 female) with ages between 15 and 20 years. Reliability estimate for the one-factor solution was .845, although some proposed RSES's underlying dimensions were lower than .70. Confirmatory factor analysis revealed that the best-fitting model was a single self-esteem factor, plus simultaneous correlated uniqueness for positively and negatively worded items. Multigroup analysis supported measurement invariance across age and physical activity participation, and partial metric invariance across gender, as three items failed to show metric equivalence. These results provide evidence that RSES has excellent psychometric properties and it is a valid self-esteem measure to be used among Portuguese youngsters.