Logic-based XML data integration: a semi-materializing approach

We first describe the approach to XML data integration in the XPathLog/LoPiX project that uses a warehouse strategy. We show that the DOM model and the XML Query Data Model are not suitable for this task since the integrated database is not necessarily a tree, but a set of overlapping (original and integrated) trees. The problem is solved by using a node-labeled graph-based data model, called XTreeGraph, for the internal XML database that represents multiple, overlapping XML trees, or tree views.In the second part, we return to the standard XML data model—by still keeping the overlapping tree idea by “simulating” it: The data is internally represented by XML where the “overlayed” resulting tree is represented by XLink elements that refer to the original sources. By using a logical, transparent data model for XLinks as investigated in [May, in: 11th WWW Conference, 2002], all queries behave as stated against the XTreeGraph. The use of links for partial materialization also turns the approach from a warehouse approach into a mixed approach that combines the advantages of the warehouse approach and of the virtual approach. The approach is again illustrated by using XPathLog as data integration language.     

Survival of the partial reinforcement extinction effect after contextual shifts

The effects of contextual shifts on the partial reinforcement extinction effect (PREE) were studied in autoshaping with rats. Experiment 1 established that the two contexts used subsequently were easily discriminable and equally salient. In Experiment 2, independent groups of rats received acquisition training under partial reinforcement (PRF) or continuous reinforcement (CRF). Significant PREEs were observed whether extinction occurred in the same or in a different context. In Experiment 3, after PRF or CRF acquisition training, each group received extinction of the same conditioned stimulus in both the same and different contexts. PREEs were observed under both conditions, although extinction was accelerated after a contextual shift. These results were discussed in relation to the role of mediational states in the PREE.     

Differential effects of aging on processes underlying task switching

In this study, we used event-related brain potentials (ERPs) to examine the effects of aging on processes underlying task switching. The response time data revealed an age-related increase in mixing costs before controlling for general slowing and no effect of aging on switching costs. In the cue-locked epoch, the ERP data revealed little effect of age on the parietal P3 related to cue encoding, an age-related decrease in parietal activity related to cue retrieval, and an age-related increase in the amplitude of the parietal and frontal activity related to task set configuration and rule mapping. In the target-locked epoch, there was differential neural recruitment in younger and older adults in response to task mixing. These data are consistent with the idea that older adults may not fully implement task set before onset of the target stimulus.     

Selecting K of N alternatives

In some decision contexts (e.g. graduate admissions) the task to select a subset of k distinct alternatives from among the N > k > 1 options available. For moderate values of N and k, the number of possible subsets of size k becomes quite large. Assuming alternatives are evaluated using consistent, though not explicit weights, selecting k, rather than 1, empirically excludes a substantial proportion (more than 80%) of the subsets; unfortunately to the unaided decision maker it is not obvious which subsets should be excluded. The tendency of subjects to select excludable subsets can be called an ‘infeasibility’ bias. The experimental evidence surprisingly shows no ‘infeasibility’ bias, as subjects overwhelmingly chose non-excluded selections.     

Logic programming as classical inference

We propose a denotational semantics for logic programming based on a classical notion of logical consequence which is apt to capture the main proposed semantics of logic programs. In other words, we show that any of those semantics can be viewed as a relation of the form $T{\models }^{\star }X$ where T is a theory which naturally represents the logic program under consideration together with a set of formulas playing the role of “hypotheses”, in a way which is dictated by that semantics, ${\models }^{\star }$ is a notion of logical consequence which is classical because negation, disjunction and existential quantification receive their classical meaning, and X represents what can be inferred from the logic program, or an intended interpretation of that logic program (such as an answer-set, its well-founded model, etc.). The logical setting we propose extends the language of classical modal logic as it deals with modal operators indexed by ordinals. We make use of two kinds of basic modal formulas: ${\square }_{\alpha }\phi$ which intuitively means that the logical program can generate φ by stage α of the generation process, and ${◇}_{\alpha }{\square }_{\beta }\phi$ with $\alpha >\beta$, which intuitively means that φ can be used as a hypothesis from stage β of the generation process onwards, possibly expecting to confirm φ by stage α (so expecting ${\square }_{\alpha }\phi$ to be generated). This allows us to capture Rondogiannis and Wadge's version of the well-founded semantics [27] where a member of the well-founded model is a closed atom which receives an ordinal truth value of ${\mathtt{true}}_{\alpha }$ or ${\mathtt{false}}_{\alpha }$ for some ordinal α: in our framework, this corresponds to having $T{\models }^{\star }{\square }_{\alpha }\phi$ or $T{\models }^{\star }{\square }_{\alpha }\neg \phi$, respectively, with T being the natural representation of the logic program under consideration and the right set of “hypotheses” as dictated by the well-founded semantics. The framework we present goes much beyond the proposed traditional semantics for logic programming, as it can for instance let us investigate under which conditions a set of hypotheses can be minimal, with each hypothesis being activated as late as possible and confirmed as soon as possible, setting the theoretical foundation to sophisticated ways of making local use of hypotheses in knowledge-based systems, while still being theoretically grounded in a classical notion of logical consequence.     

The sure thing principle,dilations, and objective probabilities

The common theme that unites the four sections is STP, the sure thing principle. But the paper can be divided neatly into two parts. The first, consisting of the first two sections, contains an analysis of STP as it figures in Savage?s system and proposals of changes to that system. Also possibilities for partially ordered acts are considered. The second, consisting of the last two sections, is about imprecise probabilities, dilations and objective probabilities. Variants of STP are considered but this part is self-contained and can be read separately. The main claim there is that dilations, which can have extremely counterintuitive consequences, can be eliminated by a more careful analysis of the phenomenon. It outlines a proposal of how to do it. Here the concept of objective probabilities plays a crucial role.     

Reversed PREE under multiple schedules: Exploration of a modulation hypothesis

When reinforcer rates are manipulated in within-subjects designs, persistence in subsequent extinction trials is sometimes greater to the response alternative associated with the higher reinforcer rate (“reversed” partial reinforcement extinction effect, RPREE). The RPREE is often held to be a contradiction to the conventional PREE. To explore the interaction between these effects, student subjects were exposed to a multiple high-density and low-density reinforcement schedule, then to extinction conditions. Subjects in two control conditions received the high- and low-density schedules only. For all groups, general extinction persistence was elevated, and a within-subjects RPREE occurred under the multiple schedule. The RPREE was caused by the low-density component increasing persistence to the high-density component; the high-density component did not decrease persistence to the low-density component. These results support the view that the RPREE may be a within-subjects effect of the conventional PREE.     

Set representations of orders and a structural equivalent of saturation

Set representations are useful in the theory of knowledge spaces. A set representation of an order is an isomorphic mapping of its base set into the power set of some set ordered by set inclusion. Such a representation is basic if the union of the representing sets of the predecessors of an element contains strictly less elements than the representing set of this element, and it is parsimonious if the difference is exactly one element. This paper investigates the properties of the minimal number of elements which must be used in a parsimonious representation. This value is studied for several order operations. Moreover, orders which allow essentially only one parsimonious set representation are structurally characterized. These orders are called saturated. Finally, the way to apply these results to knowledge spaces are outlined.     

Shielding voices: The modulation of binding processes between voice features and response features by task representations

Vocal events offer not only semantic-linguistic content but also information about the identity and the emotional-motivational state of the speaker. Furthermore, most vocal events have implications for our actions and therefore include action-related features. But the relevance and irrelevance of vocal features varies from task to task. The present study investigates binding processes for perceptual and action-related features of spoken words and their modulation by the task representation of the listener. Participants reacted with two response keys to eight different words spoken by a male or a female voice (Experiment 1) or spoken by an angry or neutral male voice (Experiment 2). There were two instruction conditions: half of participants learned eight stimulus-response mappings by rote (SR), and half of participants applied a binary task rule (TR). In both experiments, SR instructed participants showed clear evidence for binding processes between voice and response features indicated by an interaction between the irrelevant voice feature and the response. By contrast, as indicated by a three-way interaction with instruction, no such binding was found in the TR instructed group. These results are suggestive of binding and shielding as two adaptive mechanisms that ensure successful communication and action in a dynamic social environment.     

为什么会出现“舌尖现象”?——TOT现象发生机制之争

舌尖现象(tip-of-the-tongue,TOT)是一种普遍发生的现象,但是发生TOT的对象、情景、机制等却是特殊和复杂的。因此,它引起了研究者的关注,尤其是在其产生机制上更是存在着很多争论。国外研究者提出了部分激活理论、传递缺陷理论、障碍物假说、神经网络模型、元认知理论等。但研究者大多都基于单一条件或情景来探讨TOT的产生,因此提出的理论的使用范围,解释广度等均有局限。关于TOT依然有许多疑惑,同时也存在值得探讨的课题。