Mathematical modeling of group product recommendation with partial information: How many ratings do we need?

Product recommendation is one of the most important services in the Internet. In this paper, we consider a product recommendation system which recommends products to a group of users. The recommendation system only has partial preference information on this group of users: a user only indicates his preference to a small subset of products in the form of ratings. This partial preference information makes it a challenge to produce an accurate recommendation. In this work, we explore a number of fundamental questions. What is the desired number of ratings per product so to guarantee an accurate recommendation? What are some effective voting rules in summarizing ratings? How users’ misbehavior such as cheating, in product rating may affect the recommendation accuracy? What are some efficient rating schemes? To answer these questions, we present a formal mathematical model of a group recommendation system. We formally analyze the model. Through this analysis we gain the insight to develop a randomized algorithm which is both computationally efficient and asymptotically accurate in evaluating the recommendation accuracy under a very general setting. We propose a novel and efficient heterogeneous rating scheme which requires equal or less rating workload, but can improve over a homogeneous rating scheme by as much as 30%. We carry out experiments on both synthetic data and real-world data from TripAdvisor. Not only we validate our model, but also we obtain a number of interesting observations, i.e., a small of misbehaving users can decrease the recommendation accuracy remarkably. For TripAdvisor, one hundred ratings per product is sufficient to guarantee a high accuracy recommendation. We believe our model and methodology are important building blocks to refine and improve applications of group recommendation systems.     

How do we measure and improve the quality of a hierarchical ontology?

Hierarchical ontologies enable organising information in a human-machine understandable form, but constructing them for reuse and maintainability remains difficult. Often supporting tools available lack formal methodological underpinning and their developers are not supported by any concomitant metrics. The paper presents a formal underpinning to provide quality metrics of a taxonomy hierarchical ontology and proposes a methodology for semi-automatic building of maintainable taxonomies. Users provide terms to be used to describe different ontological elements as well as their attributes and their ranges of values. The methodology uses the formalised metrics to assess the quality of the users input and proposes changes according to given quality constraints. The paper illustrates the metrics and the methodology in constructing and repairing two medium size well-known taxonomies.     

Visual capability to receive character information Part II: How long do we need to memorize the random characters briefly presented?

Abstract

The time-related aspect of the capability to receive character information was measured and analysed. As a result, when the presentation time was shorter than one second, ability was almost constant, but when it exceeded one second it increased as the presentation time increased.

It was found that when a pattern was presented without limiting the presentation time, there were linear relationships between the number of characters to be memorized and the time required to memorize all the characters correctly in the range of 2 to 6 characters, 7 to 12 and 13 to 16 (or more). These boundaries corresponded well to a unit of memory well known as the magical number 7 plus minus 2. From these results, it was estimated that a grouping mechanism exists even when memorizing characters and that it has a hierarchical structure.     

Newton's method revisited: How accurate do we have to be?

We analyze the convergence of quasi-Newton methods in exact and finite precision arithmetic using three different techniques. We derive an upper bound for the stagnation level and we show that any sufficiently exact quasi-Newton method will converge quadratically until stagnation. In the absence of sufficient accuracy, we are likely to retain rapid linear convergence. We confirm our analysis by computing square roots and solving bond constraint equations in the context of molecular dynamics. In particular, we apply both a symmetric variant and Forsgren's variant of the simplified Newton method. This work has implications for the implementation of quasi-Newton methods regardless of the scale of the calculation or the machine.     

Does India need to harmonize the law of patent exhaustion and parallel imports?

The amendment of patent law of India in 2005 to fulfill her international obligation under the TRIPS Agreement (World Trade Organization Agreement on Trade Related Intellectual Property Rights) was an outcome of an attempt to balance the competing interests of several stakeholders, including indigenous pharmaceutical companies, multi-national pharmaceutical companies, non-governmental organizations and civil society groups concerned with access to affordable drugs. The adverse consequence of this delicate balancing is introduction of some provisions in the Act whose compatibility with the TRIPS Agreement is questionable, and which therefore are prone to litigations. Section 107A(b) of the amended patent law dealing with parallel imports is one such provision, which, if interpreted word for word could have significant connotations for the rights of a patent owner. This article aims to examine the inconsistencies intrinsic in Section 107A(b) and discusses the divergences in the Indian patent law associated with the doctrine of exhaustion and parallel imports. This article also proposes legal amendments with a view to eliminate inconsistencies intrinsic in the section and enlarge the ambit of the exhaustion principle conceptualized therein, while concurrently remaining compliant with the TRIPS Agreement.     

Visual capability to receive character information Part I: How many characters can we recognize at a glance?

Abstract

A study was made on the capability to receive character information and the factors restricting it. The study showed that the capability indicated by the memory span was limited by the average number of characters for words that are made up of individual characters, and calculated in terms of information quantity, there was no difference among the individual characters. The differences in memory span, depending on the size of the pattern presented, was negligible. The difference in the way characters were arranged produced the difference in memory span saturation. This phenomenon is explained by the nature of the lateral interference effect working among the adjacent characters.     

How close are we to solving the problem of automated visual surveillance?

The problem of automated visual surveillance has spawned a lively research area, with 2005 seeing three conferences or workshops and special issues of two major journals devoted to the topic. These alone are responsible for somewhere in the region of 240 papers and posters on automated visual surveillance before we begin to count those presented in more general fora. Many of these systems and algorithms perform one small sub-part of the surveillance task, such as motion detection. But even with low level image processing tasks it is often difficult to compare systems on the basis of published results alone. This review paper aims to answer the difficult question “How close are we to developing surveillance related systems which are really useful?” The first section of this paper considers the question of surveillance in the real world: installations, systems and practises. The main body of the paper then considers existing computer vision techniques with an emphasis on higher level processes such as behaviour modelling and event detection. We conclude with a review of the evaluative mechanisms that have grown from within the computer vision community in an attempt to provide some form of robust evaluation and cross-system comparability.     

How do we program the home? Gender,attention investment,and the psychology of programming at home

We report a series of studies investigating the choices that users make between direct manipulation and abstract programming strategies when operating domestic appliances. We characterise these strategic choices in terms of the Attention Investment model of abstraction use. We then describe an experiment that investigates the estimation biases influencing the individual parameters of that model. These biases are linked to gender in a way that explains some gender differences in discretionary appliance use. Finally, we suggest design strategies that might compensate for those gender-linked estimation biases, and therefore make programmable features of future homes more accessible to a wider range of users.     

How Long Do We Expect to Live? A Review of the Evidence

How long people expect to live sets an important context for longevity risk in retirement planning and may contribute to the acceptability of policies to raise pension age. However, there have been few studies representative of a national population on subjective longevity. This paper reviews the available evidence. It finds that despite some studies reporting that subjective longevity is close to average measures in population life tables the prevailing tendency is to underestimate lifespans. Men generally reflect that they have lower actual longevity than women on average, but men are more optimistic, so that women are more likely to underestimate their likely longevity. People may take account of some mortality risk factors in estimating their own longevity, but appear not to understand the true extent of risk. There is little data on how people think about longevity or why they choose a particular estimate of their own likely lifespan. Thus, international evidence suggests potential for longevity risk in individual retirement planning and raises significant questions about the policy implications which can only become more acute in ageing populations.     

Waiting for the rapture: What can we do with computers to (hopefully) witness the emergence of life?

Natural Computing - Hadn’t this question already been answered? We all know about computation-universal Turing Machines. And we know that any such machine can simulate a space–time...     

How do tax compliance labels impact sharing platform consumers? An empirical study on the interplay of trust,moral, and intention to book

The platform economy has generated various new and highly successful business models. However, certain models facilitate tax evasion for service providers on their income earned on these platforms. While tax evasion contradicts the pro-social claim of many sharing platforms, it is unclear whether a provider’s tax honesty constitutes a value for consumers at all. This study investigates the role of tax compliance for platform users by employing an online experiment ((n=286)). The results indicate that consumers perceive providers’ tax compliance and consider it as a trust-enhancing signal. In further analysis, we find that consumers’ moral norms moderate both the signal’s trust-building effect as well as the relation between trust and transaction intention. In light of recent policy debates around taxing the platform economy, this study provides valuable practical insights for tax legislators.

     

How have we arrived at the present state of knowledge in process control? Is there a lesson to be learned?

The utilization of the results of control theory in the process control field has been lagging behind other application fields such as aerospace by many years. It is argued that the availability of high capacity computing at low price will change this situation and that new powerful control techniques can now be implemented in process control.     

What seams do we remove in mobile-assisted seamless learning? A critical review of the literature

Seamless learning refers to the seamless integration of the learning experiences across various dimensions including formal and informal learning contexts, individual and social learning, and physical world and cyberspace. Inspired by the exposition by Chan et al. (2006) on the seamless learning model supported by the setting of one or more mobile device per learner, this paper aims to further investigate the meaning of seamless learning and the potential ways to put it in practice. Through a thorough review of recent academic papers on mobile-assisted seamless learning (MSL), we identify ten dimensions that characterize MSL. We believe that such a framework allows us to identify research gaps in the stated area. A practitioner interested in adopting an MSL design or doing a new design can use our analysis to situate the dimensional space where the constraints or parameters of his or her design problem lie, and look at relevant design and research-based evidence of other related MSL systems to refine her own design.     

How do I update my model? On the resilience of Predictive Process Monitoring models to change

Knowledge and Information Systems - Existing well-investigated Predictive Process Monitoring techniques typically construct a predictive model based on past process executions and then use this...     

How sensitive is a vineyard crop model to the uncertainty of its runoff module?

Many crop models use the NRCS Curve Number method to estimate runoff, but the simplified assumptions of this method are rarely considered in model uncertainty assessments. The associated uncertainty may be high for cropping systems with a significant part of bare soil like vineyards, specifically under a Mediterranean climate. In this work, we evaluate for a vineyard crop model the structure uncertainty coming from its uncertain runoff module. We introduce a new method based on additional knowledge about the runoff process and on a mathematical property of the model structure. Situations characterized in terms of soil water content and mean runoff conditions are studied for two applications of the vineyard model and guidelines for model users are derived. This work shows that uncertainty quantification can benefit from the knowledge of mathematical properties of a model and provide clear guidelines to model users.     

Finding the key length of a Vigenère cipher: How to improve the twist algorithm

Abstract

A Vigenère cipher applies a single short key repeatedly to encrypt a plaintext. If a cryptanalyst correctly finds out the key length, the ciphertext can be divided into multiple instances of shift cipher and be broken by frequency analysis. To determine the key length, the twist algorithm, an alternate method to the standard Kasiski and Friedman tests, was recently proposed. In this article, we propose the twist⁺ algorithm, an improved twist algorithm, which can estimate the key length more accurately than the original twist algorithm.     

The role of users in interactive systems design: When computers are theatre,do we want the audience to write the script?

User participation in the design process may be an axiom of quality design but in the design of interactive, innovative computer systems, user participation may be neither feasible nor desirable. Here, user centred methodologies miss the point. If computers are a medium rather than a tool, then we need a new design paradigm that recognizes the difference between using a product and experiencing a show. In this paper the role of users in interactive systems design within the context of Multimedia product development is discussed. The main features of Multimedia product development are outlined through reference to an empirical study of two organizations and the role of users in the design process is discussed. Finally a different design paradigm is suggested.     

How does a box work? A study in the qualitative dynamics of solid objects

This paper is an in-depth study of qualitative physical reasoning about one particular scenario: using a box to carry a collection of objects from one place to another. Specifically we consider the plan, plan1 “Load objects uCargo into box oBox one by one; carry oBox from location l1 to location l2”. We present qualitative constraints on the shape, starting position, and material properties of uCargo and oBox and on the characteristics of the motion that suffice to make it virtually certain that plan1 can be successfully executed. We develop a theory, consisting mostly of first-order statements together with two default rules, that supports an inference of the form “If conditions XYZ hold, and the agent attempts to carry out plan1 then presumably he will succeed”. Our theory is elaboration tolerant in the sense that carrying out the analogous inference for carrying objects in boxes with lids, in boxes with small holes, or on trays can reuse much of the same knowledge. The theory integrates reasoning about continuous time, Euclidean space, commonsense dynamics of solid objects, and semantics of partially specified plans.     

How to divide a territory? A new simple differential formalism for optimization of set functions

In many practical problems, we must optimize a set function, i.e., find a set A for which f(A)→max, where f is a function defined on the class of sets. Such problems appear in design, in image processing, in game theory, etc. Most optimization problems can be solved (or at least simplified) by using the fact that small deviations from an optimal solution can only decrease the value of the objective function; as a result, some derivative must be equal to 0. This approach has been successfully used, e.g., for set functions in which the desired set A is a shape, i.e., a smooth (or piece-wise smooth) surface. In some real-life problems, in particular, in the territorial division problem, the existing methods are not directly applicable. For such problems, we design a new simple differential formalism for optimizing set functions. ©1999 John Wiley & Sons, Inc.     

An epidemiological assessment of online groups and a test of a typology: What are the (dis)similarities of the online group types?

A vast multitude of online groups exist, and authors have been rapidly investigating their dynamics. Extant studies have provided great information on the effects of online group membership, but limitations are often noted in these studies. Amongst the most concerning limitations are issues of generalizability. Authors are often unsure whether their results are able to generalize to other online groups, including those that are seemingly similar. For this reason, some researchers have created typologies of online groups, in hopes that online groups that fall within the same category will be generalizable; however, no study has analyzed the merit of an online group typology, and conclusions are based upon speculation. For this reason, the current study analyzed the dynamics of three different online groups, which fall within separate categories of an online group typology: a cancer support forum, a LGBT forum, and a Harry Potter fan forum. The results demonstrate that these groups vary in their properties, including group members’ group identity, well-being, and social support. These results provide support for an online group typology, and precisely demonstrate in what manner these groups differ. Additionally, the results offer valuable information about the individual groups, as some variables were previously unstudied in some group types. The discovery of these previously unknown dynamics leads to the potential of new studies, which is discussed. Therefore, the current study provides important implications for future studies, as well as the interpretation of future research results.