Jakub Swacha

Combining efficient XML compression with query processing

This paper describes a new XML compression scheme that offers both high compression ratios and short query response time. Its core is a fully reversible transform featuring substitution of every word in an XML document using a semi-dynamic dictionary, effective encoding of dictionary indices, as well as numbers, dates and times found in the document, and grouping data within the same structural context in individual containers. The results of conducted tests show that the proposed scheme attains compression ratios rivaling the best available algorithms, and fast compression, decompression, and query processing.

Fast Transform for Effective XML Compression

The main drawback of the XML format seems to be its verbosity, a key problem especially in case of large documents. Therefore, efficient encoding of XML constitutes an important research issue. In this work, we describe a preprocessing transform meant to be used with popular LZ77-style compressors. We show experimentally that our transform, albeit quite simple, leads to better compression ratios than existing XML-aware compressors. Moreover, it offers high decoding speed, which often is of utmost priority.

A highly efficient XML compression scheme for the web

Contemporary XML documents can be tens of megabytes long, and reducing their size, thus allowing to transfer them faster, poses a significant advantage for their users. In this paper, we describe a new XML compression scheme which outperforms the previous state-of-the-art algorithm, SCMPPM, by over 9% on average in compression ratio, having the practical feature of streamlined decompression and being almost twice faster in the decompression. Applying the scheme can significantly reduce transmission time/bandwidth usage for XML documents published on the Web. The proposed scheme is based on a semi-dynamic dictionary of the most frequent words in the document (both in the annotation and contents), automatic detection and compact encoding of numbers and specific patterns (like dates or IP addresses), and a back-end PPM coding variant tailored to efficiently handle long matching sequences. Moreover, we show that the compression ratio can be improved by additional 9% for the price of a significant slow-down.

An Architecture of a Gamified Learning Management System

The growing popularity of using gamification in education, and especially in e-learning, propels interest in Learning Management Systems that incorporate gamification mechanisms. This paper describes the architecture of a Learning Management System that is gamified by design, focusing at its key components. It also discusses the requirements for an LMS due to introduction of game-based elements and the role of specific LMS components in implementing them.

OFR: An Efficient Representation of RDF Datasets

The constant growth of structured data, often in the form of RDF, demands for efficient compression methods, to facilitate their storage and transmission. We propose an RDF compression algorithm that produces a succinct representation of RDF datasets. It consists of two stages. The first splits the input triples into multiple streams, and applies tailored compaction techniques for each stream. In the second, a general-purpose compression is applied. We experimentally show on a number of datasets that the proposed algorithm achieves compression ratios significantly better than the RDF compressors known from the literature.

Assessing the Efficiency of Data Compression and Storage System

The fast growth of stored data volume raises the importance of proper data storage management, for both technological and economic reasons. There is need for measures that would allow to evaluate storage system efficiency in all its aspects, not limited to capacity utilization, and including the performance impact of data compression. In this paper, more than ten technical efficiency measures for data compression and storage are discussed. The main contribution is an economic efficiency measure, which combines multiple relevant performance factors using the related costs or profits as a weight of their respective importance. The proposed efficiency assessment procedure can be applied to any kind of storage systems. It is also supported with software to gather and manage the required input data, calculate the measures, and present the results in user-customized form.

Estimating the Cost of Computer System Working Time

This paper discusses the most important aspects determining the value of computer system working time, methods for measuring them, and formulas combining the measurements into a synthetic estimate of the cost of computer system working time. The estimated costs can be useful in pointing at system tasks worth optimization, and can help evaluate profitability of possible system upgrade.

The predictive-substitutional compression scheme and its effective implementation

The predictive-substitutional compression scheme combines string-oriented and symbol-oriented models to improve compression speed and effectiveness. There are several hybrid compression algorithms known. In this paper, two new one-pass predictive-substitutional algorithms are introduced. The improved algorithm (PLZ+) implements fast switching cost evaluation making it capable of doing a substitution only when the substitution identifiers codeword length is shorter than the sum of codeword lengths of the literals that the string is composed of. Experimental results show the predictive-substitutional scheme is one of the best available data compression methods for data transmission purposes in medium bandwidth range.

Representation of Events and Rules in Gamification Systems

Abstract The paper proposes a domain-agnostic description of user-generated events which conveys their key properties of relevance for gamification (i.a. context, actor, action, object, location and time) and a notation, based on this description, which allows to effectively specify gamification rules depending only on the content of the generated stream of events. This way, no hooks have to be inserted in the gamified system other than reporting of basic events happening within it. The proposed notation allows to design gamification rules that can be applied to different gamified systems, only provided they can generate event reports using the proposed representation (and belong to the same domain so that the rules remain relevant). It also simplifies building of rule-processing systems that serve various gamified systems. It is especially useful for complex gamification systems with multiple sources of rules and multiple points of their processing.

Project management and communication software selection using the weighted regularized Hasse method

This paper addresses the problem of selecting the most appropriate project management and communication software for a project having specific requirements. A four-stage procedure featuring the weighted regularized Hasse method is used to compare and rank the candidate tools. The ranking of the tools takes into consideration the importance of the functional and non-functional features of the project management systems with their respective weights based on the results of a questionnaire conducted among members of a dispersed international project team.