On the extraction, ordering, and usage of landmarks in planning

Many known planning tasks have inherent constraints concerning the best order in which to achieve the goals. A number of research efforts have been made to detect such constraints and use them for guiding search, in the hope to speed up the planning process. We go beyond the previous approaches by dening ordering constraints not only over the (top level) goals, but also over the sub-goals that will arise during planning. Landmarks are facts that must be true at some point in every valid solution plan. We show how such landmarks can be found, how their inherent ordering constraints can be approximated, and how this information can be used to decompose a given planning task into severa smaller sub-tasks. Our methodology is completely domain- and planner-independent. The implementation demonstrates that the approach can yield significant performance improvements in both heuristic forward search and GRAPHPLAN-style planning

A negotiation framework for heterogeneous group recommendation

Over the last years, some remarkable recommender systems for group of users have been developed. When using most of these systems, each group member communicates his/her preferences to the system, which obtains a group profile as the result of an equal weighting of the individual preferences. This way, no member is particularly dissatisfied with the recommendations. However, this is not a realistic situation, given that not all the members in a group act in the same manner. This paper deals with the problem of recommendation for a group of users, where, besides his/her own preferences, each user may have different expectations about the result of the recommendation and may exhibit a different behaviour with respect to the other group members. Moreover, all this information is private and may be revealed under certain circumstances. In this context, we have opted for building a multi-agent system, where an agent acts on behalf of one group member. We have implemented a UserAgent that can be configured in order to exhibit the behaviour desired by the corresponding user. Then, different UserAgents negotiate with the aim of building a group profile that satisfies their particular minimum requirements, while preserving some privacy. Moreover, we have designed a NegotiatorAgent, which governs the negotiation and may act as a mediator in order to facilitate the agreement. Finally, we have performed some experiments that show that this mechanism is able to give a response in this heterogeneous environment.Partial support provided by Consolider Ingenio 2010 CSD2007-00022, Spanish Government Project MICINN TIN2011-27652- C03-01.García García, I.; Sebastiá Tarín, L. (2014). A negotiation framework for heterogeneous group recommendation. Expert Systems with Applications. 41(4):1245-1261. doi:10.1016/j.eswa.2013.07.111S1245126141

Physicochemical comparison of precipitated calcium carbonate for different configurations of a biogas upgrading unit

BACKGROUND: This paper presents a physicochemical comparison of the solid products obtained from two alternative processes that recycle waste sodium carbonate (Na2CO3) solution, which is produced following the absorption of CO2 in a biogas upgrading unit. Chemical regeneration processes offer an attractive alternative to the energetically demanding standard physical methods. In the first process, sodium hydroxide (NaOH) is regenerated as a precipitate from the chemical reaction of Na2CO3 with calcium hydroxide (Ca(OH)2). The second process shows a path to obtain a valuable sodium chloride (NaCl) and calcium carbonate (CaCO3) rich brine from calcium chloride (CaCl2) acting as a precipitant agent. In both processes, precipitated calcium carbonate (PCC) is obtained as the most valuable by‐product, but with varying properties owing to the different origin. RESULTS: The purpose of this work is to analyze physicochemically both variations of PCCs obtained and examine the differences between these solid samples in order to determine which method produces more desirable characteristics in the final product. To this end, Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, X‐ray diffraction (XRD) and scanning electron microscopy (SEM) were employed as characterization methods. The results reflect that both PCCs have a calcite crystal structure, or morph, being as both PCC products originate from CaCl2 that is more similar to commercial calcium carbonate calcite. CONCLUSION: These results confirmed that a pure CaCO3 valuable by‐product can be obtained from a biogas upgrading unit with several industrial applications.This work was supported by the University of Seville through V PPIT-US. Financial support for this work was also provided by EPSRC grant EP/R512904/1 as well as Royal Society Research Grant RSGR1180353. This work was also partially sponsored by CO2ChemUK through EPSRC grant EP/P026435/1. Furthermore, this work was supported by EMASESA through the NURECCO2 project and Corporación Tecnológica de Andalucía (CTA)

Preference elicitation techniques for group recommender systems

A key issue in group recommendation is how to combine the individual preferences of different users that form a group and elicit a profile that accurately reflects the tastes of all members in the group. Most Group Recommender Systems (GRSs) make use of some sort of method for aggregating the preference models of individual users to elicit a recommendation that is satisfactory for the whole group. In general, most GRSs offer good results, but each of them have only been tested in one application domain. This paper describes a domain-independent GRS that has been used in two different application domains. In order to create the group preference model, we select two techniques that are widely used in other GRSs and we compare them with two novel techniques. Our aim is to come up with a model that weighs the preferences of all the individuals to the same extent in such a way that no member in the group is particularly satisfied or dissatisfied with the final recommendations. © 2011 Elsevier Inc. All rights reserved.Partial support provided by Consolider Ingenio 2010 CSD2007-00022, Spanish Government Project MICINN TIN2008-6701-C03-01 and Valencian Government Project Prometeo 2008/051. FPU grant reference AP2009-1896 awarded to Sergio Pajares-Ferrando.García García, I.; Pajares Ferrando, S.; Sebastiá Tarín, L.; Onaindia De La Rivaherrera, E. (2012). Preference elicitation techniques for group recommender systems. Information Sciences. 189:155-175. https://doi.org/10.1016/j.ins.2011.11.037S15517518

Temporal landmark graphs for solving overconstrained planning problems

This paper presents TempLM, a novel approach for handling temporal planning problems with deadlines. The proposal revolves around the concept of temporal landmark, a proposition that must be necessarily true in all solution plans to achieve the problem goals within their deadlines. The temporal landmarks extracted from the problem form a landmarks graph where nodes are landmarks and edges represent temporal as well as causal relationships between landmarks. The graph comprises information about which propositions and when these propositions must be achieved in a solution plan, information that is later used to guide the search process as well as reduce the search space. Thus, the partial plans of the search tree that are not compliant with the information comprised in this graph are pruned. We present an exhaustive experimentation evaluation in overconstrained and unsolvable problems and we compare the performance of TempLM with other state-of-the-art planners. The results will show the efficiency of TempLM in the detection of unsolvable problems. (C) 2016 Elsevier B.V. All rights reserved:We thank Derek Long for solving our doubts about the modal operators in PDDL3 and Erez Karpas for supplying the compiled domain and problem files with their temporal landmarks. This work has been partially supported by Spanish Government Project MINECO TIN2014-55637-C2-2-R.Marzal Calatayud, EJ.; Sebastiá Tarín, L.; Onaindia De La Rivaherrera, E. (2016). Temporal landmark graphs for solving overconstrained planning problems. Knowledge-Based Systems. 106:14-25. https://doi.org/10.1016/j.knosys.2016.05.029S142510

e-Tourism: a tourist recommendation and planning application

e-Tourism is a tourist recommendation and planning application to assist users on the organization of a leisure and tourist agenda. First, a recommender system offers the user a list of the city places that are likely of interest to the user. This list takes into account the user demographic classification, the user likes in former trips and the preferences for the current visit. Second, a planning module schedules the list of recommended places according to their temporal characteristics as well as the user restrictions; that is the planning system determines how and when to realize the recommended activities. Having the list of recommended activities organized as an agenda (i.e. an executable plan), is a relevant characteristic that most recommender systems lack.This work has been partially funded by Consolider Ingenio 2010 CSD2007-00022 project, by the Spanish Government MICINN TIN2008-6701-C03-01 project and by the Valencian Government GVPRE/2008/384 project. We thank J. Benton for having provided us with the system Sapa to execute our experiments.Sebastiá Tarín, L.; García García, I.; Onaindia De La Rivaherrera, E.; Gúzman Álvarez, CA. (2009). e-Tourism: a tourist recommendation and planning application. International Journal on Artificial Intelligence Tools. 18(5):717-738. https://doi.org/10.1142/S0218213009000378S71773818

The impact of surgical practice on oncological outcomes in robot-assisted radical hysterectomy for early-stage cervical cancer, Spanish National Registry

Minimal invasive surgery (MIS) has been associated with lower disease-free survival than open surgery among women who underwent radical hysterectomy for early-stage cervical cancer. However, the mechanisms by which MIS increases mortality in cervical cancer remain uncertain. We aimed to determine if surgical practice among centers using robotic surgery has an impact on oncological outcomes. We evaluated 215 women with early-stage cervical cancer (≤IB1 or IIA1, FIGO 2009) who underwent robot-assisted radical hysterectomy in five Spanish tertiary centers between 2009 and 2018. A higher surgical volume, higher participation in clinical trials, higher rate of MRI use for diagnosis, greater use of sentinel lymph node biopsies, and a favorable learning curve with low rates of early recurrences were observed for the centers with better oncological outcomes. These factors might have a significant impact on oncological outcomes in all surgical approaches. Abstract: This study aimed to assess whether surgical practice had a significant impact on oncological outcomes among women who underwent robot-assisted radical hysterectomy for early-stage cervical cancer (≤IB1 or IIA1, FIGO 2009). The secondary objective was to audit the pre-surgical quality indicators (QI) proposed by the European Society of Gynaecological Oncology (ESGO). The top 5 of 10 centers in Spain and Portugal were included in the analysis. The hospitals were divided into group A (n = 118) and group B (n = 97), with recurrence rates of 10%, respectively. After balancing both groups using the propensity score, the ORs for all events were higher and statistically significant for group B (recurrences OR = 1.23, 95% CI = 1.13-1.15, p-value = 0.001; death OR = 1.10, 95% CI = 1.02-1.18, p-value = 0.012; disease-specific mortality ORr = 1.11, 95% CI = 1.04-1.19, p-value = 0.002). A higher surgical volume, higher participation in clinical trials, higher rate of MRI use for diagnosis, greater use of sentinel lymph node biopsies, and a favorable learning curve with low rates of early recurrences were observed among the centers with better oncological outcomes. These factors might have a significant impact on oncological outcomes not only after robot-assisted surgery, but also after laparoscopies and open surgeries in the treatment of cervical cancer