Archive for » December, 2012 «

Thursday, December 20th, 2012 | Author:

On 20 December 2012, Jasper Stoop defended his MSc thesis on process mining for fraud detection in the procurement process. The MSc project was carried out at KPMG.
“Process Mining and Fraud Detection: A case study on the theoretical and practical value of using process mining for the detection of fraudulent behavior in the procurement process”[download]
This thesis presents the results of a six month research period on process mining and fraud detection. This thesis aimed to answer the research question as to how process mining can be utilized in fraud detection and what the benefits of using process mining for fraud detection are. Based on a literature study it provides a discussion of the theory and application of process mining and its various aspects and techniques. Using both a literature study and an interview with a domain expert, the concepts of fraud and fraud detection are discussed. These results are combined with an analysis of existing case studies on the application of process mining and fraud detection to construct an initial setup of two case studies, in which process mining is applied to detect possible fraudulent behavior in the procurement process. Based on the experiences and results of these case studies, the 1+5+1 methodology is presented as a first step towards operationalizing principles with advice on how process mining techniques can be used in practice when trying to detect fraud. This thesis presents three conclusions: (1) process mining is a valuable addition to fraud detection, (2) using the 1+5+1 concept it was possible to detect indicators of possibly fraudulent behavior (3) the practical use of process mining for fraud detection is diminished by the poor performance of the current tools. The techniques and tools that do not suffer from performance issues are an addition, rather than a replacement, to regular data analysis techniques by providing either new, quicker, or more easily obtainable insights into the process and possible fraudulent behavior.

Monday, December 10th, 2012 | Author:

Brend Wanders, a PhD student of mine, presents a poster at the BeNeLux Bioinformatics Conference (BBC 2012) in Nijmegen.
Pay-as-you-go data integration for bio-informatics
Brend Wanders
Background: Scientific research in bio-informatics is often data-driven and supported by biological databases. In a growing number of research projects, researchers like to ask questions that require the combination of information from more than one database. Most bio-informatics papers do not detail the integration of different databases. As roughly 30% of all tasks in workflows are data transformation tasks, database integration is an important issue. Integrating multiple data sources can be difficult. As data sources are created, many design decisions are made by their creators.
Methods: Our research is guided by two use cases: homologues, the representation and integration of groupings; metabolomics integration, with a focus on the TCA cycle
Results: We propose to approach the time consuming problem of integrating multiple biological databases through the principles of ‘pay-as-you-go’ and ‘good-is-good-enough’. By assisting the user in defining a knowledge base of data mapping rules, trust information and other evidence we allow the user to focus on the work, and put in as little effort as is necessary for the integration. Through user feedback on query results and trust assessments, the integration can be improved upon over time.
Conclusions: We conclude that this direction of research is worthy of further exploration. [details]

Friday, December 07th, 2012 | Author:

On 7 December 2012, Paul Stapersma defended his MSc thesis “Efficient Query Evaluation on Probabilistic XML Data”. The MSc project was supervised by me, Maarten Fokkinga and Jan Flokstra. The thesis is the result of a more than 2 year cooperation between Paul and me to build a probabilistic XML database system on top of a relational one: MayBMS.
“Efficient Query Evaluation on Probabilistic XML Data”[download]
In many application scenarios, reliability and accuracy of data are of great importance. Data is often uncertain or inconsistent because the exact state of represented real world objects is unknown. A number of uncertain data models have emerged to cope with imperfect data in order to guarantee a level of reliability and accuracy. These models include probabilistic XML (P-XML) –an uncertain semi-structured data model– and U-Rel –an uncertain table-structured data model. U-Rel is used by MayBMS, an uncertain relational database management system (URDBMS) that provides scalable query evaluation. In contrast to U-Rel, there does not exist an efficient query evaluation mechanism for P-XML.
In this thesis, we approach this problem by instructing MayBMS to cope with P-XML in order to evaluate XPath queries on P-XML data as SQL queries on uncertain relational data. This approach entails two aspects: (1) a data mapping from P-XML to U-Rel that ensures that the same information is represented by database instances of both data structures, and (2) a query mapping from XPath to SQL that ensures that the same question is specified in both query languages.
We present a specification of a P-XML to U-Rel data mapping and a corresponding XPath to SQL mapping. Additionally, we present two designs of this specification. The first design constructs a data mapping in such way that the corresponding query mapping is a traditional XPath to SQL mapping. The second design differs from the first in the sense that a component of the data mapping is evaluated as part of the query evaluation process. This offers the advantage that the data mapping is more efficient. Additionally, the second design allows for a number of optimizations that affect the performance of the query evaluation process. However, this process is burdened with the extra task of evaluating the data mapping component.
An extensive experimental evaluation on synthetically generated data sets and real-world data sets shows that our implementation of the second design is more efficient in most scenarios. Not only is the P-XML data mapping executed more efficient, the query evaluation performance is also improved in most scenarios.