Evaluating Digital Libraries: A Longitudinal and Multifaceted View

published or submitted for publicatio

Judging a book by its cover: interface elements that affect reader selection of ebooks

Digital library research has demonstrated the impact of content presentation on both search and reading behaviours. In this paper, we scrutinise the influence of ebook presentation on user behaviour, focussing on document thumbnails and the first page view. We demonstrate that flaws in presentation increase the volume of short time-span reading, and reduce the likelihood of long-span reading when compared to other documents. This reflects other patterns of information seeking behaviour that demonstrate increased short-term reading when information content is uncertain, and suggests an ineffective use of reader time on less useful content

Poultry in Motion: A Study of International Trade Finance Practices

This paper analyzes the financing terms that support international trade and sheds light on how and why these arrangements affect trade. Using detailed transaction level data from a U.S. based exporter of frozen and refrigerated food products, primarily poultry, it begins by describing broad patterns about the use of alternative financing terms. These patterns help discipline a model in which the trade finance mode is shaped by the risk that an importer defaults on an exporter and by the possibility that an exporter does not deliver goods as specified in the contract. The empirical results indicate that transactions are more likely to occur on cash in advance or letter of credit terms when the importer is located in a country with weak contractual enforcement and in a country that is further from the exporter. Letters of credit, however, are rarely used by the exporter. As an importer develops a relationship with the exporter, transactions are less likely to occur on terms that require prepayment. During the recent crisis, the exporter was more likely to demand cash in advance terms when transacting with new customers, and customers that traded on cash in advance terms prior to the crisis disproportionately reduced their purchases. These results can be rationalized by the model whenever (i) misbehavior on the part of the exporter is of little concern to importers, and (ii) local banks in importing countries are typically more effective than the exporter in pursuing financial claims against importers.

Efficient Management of Short-Lived Data

Motivated by the increasing prominence of loosely-coupled systems, such as mobile and sensor networks, which are characterised by intermittent connectivity and volatile data, we study the tagging of data with so-called expiration times. More specifically, when data are inserted into a database, they may be tagged with time values indicating when they expire, i.e., when they are regarded as stale or invalid and thus are no longer considered part of the database. In a number of applications, expiration times are known and can be assigned at insertion time. We present data structures and algorithms for online management of data tagged with expiration times. The algorithms are based on fully functional, persistent treaps, which are a combination of binary search trees with respect to a primary attribute and heaps with respect to a secondary attribute. The primary attribute implements primary keys, and the secondary attribute stores expiration times in a minimum heap, thus keeping a priority queue of tuples to expire. A detailed and comprehensive experimental study demonstrates the well-behavedness and scalability of the approach as well as its efficiency with respect to a number of competitors.Comment: switched to TimeCenter latex styl

Data preperation and pattern discovery for web usage mining

The World Wide Web (WWW) continues to grow at an astounding rate in both the sheer volume of traffic and the size and complexity of Web sites. The complexity of tasks such as Web site design, Web server design, and of simply navigating through a Web site have increased along with this growth. An important input to these design tasks is the analysis of how a Web site is being used. Usage analysis includes straightforward statistics, such as page access frequency, as well as more sophisticated forms of analysis, such as finding the common traversal paths through a Web site. Web Usage Mining is the application of data mining techniques to usage logs of large Web data repositories in order to produce results that can be used in the design tasks mentioned above. However, these server logs cannot be used directly for patter discovery and analysis purposes. There are several preprocessing tasks that must be performed prior to applying data mining algorithms to the data collected from server logs. The objective of this paper is to discuss several data preparation techniques in order to identify unique users and user sessions. New heuristics to identify user sessions have been proposed. Also the data mining algorithms that can be applied to this processed data to discover patterns and rules have been discussed. On the basis of implementation of these algorithms, a comparative analysis among some of these algorithms is drawn on a 2-dimensional graph