Query inseparability by games

We investigate conjunctive query inseparability of description logic knowledge bases (KBs) with respect to a given signature, a fundamental problem for KB versioning, module extraction, forgetting and knowledge exchange. We develop a game-theoretic technique for checking query inseparability of KBs expressed in fragments of Horn-ALCHI, and show a number of complexity results ranging from P to ExpTime and 2ExpTime. We also employ our results to resolve two major open problems for OWL 2 QL by showing that TBox query inseparability and the membership problem for universal UCQ-solutions in knowledge exchange are both ExpTime-complete for combined complexity

Query-based entailment and inseparability for ALC ontologies

We investigate the problem whether two ALC knowledge bases are indistinguishable by queries over a given vocabulary. We give model-theoretic criteria and prove that this problem is undecid- able for conjunctive queries (CQs) but decidable in 2EXPTIME for unions of rooted CQs. We also consider the problem whether two ALC TBoxes give the same answers to any query in a given vocabulary over all ABoxes, and show that for CQs this problem is undecidable, too, but becomes decidable and 2EXPTIME-complete in Horn-ALC, and even EXPTIME-complete in Horn-ALC when restricted to (unions of) rooted CQs

The Local Drug Economy: The Case of Hashish Production in a post-Soviet Kyrgyz Village

This multi-method study is about small-scale illegal production of hashish in a mountainous village in north-eastern part of Kyrgyzstan. It demonstrates that drug production in Toolu is the result of a combination of factors: 1) economic transformations undertaken during the 1990s in most of the post-Soviet countries and the difficult conditions under which the agricultural mountainous economy operated as a result; 2) the legitimation of hashish making by drug producing community due to perceived injustice towards people who had to survive without any state support while the elite was corrupted and governance of drug control was inconsistent; and 3) the integration of illegal hashish production to the local economy and culture. My findings derive from extensive fieldwork based on a case study of Toolu village, located in the Tyup region of Issyk-Kul oblast. I spent nine months in Tyup, between 2009 and 2010 undertaking a mixed method study in which I collected sixty semi-structured interviews with farmers, two interviews with the representatives of law enforcement, made a participant observation of farmer’s livelihoods, and conducted a survey of 147 households. The study fills the gap in the drug market literature by presenting the case of hashish production that started as an economic necessity but was pushed into the sphere of traditional and cultural practices that helped the local population to legitimate this illegal activity. It further contributes to the debate on drug markets presenting the drug producers as farmers that deal with the economic, social and political issues as any other citizens of the country. Hashish production was not part of the agricultural activities of the local population of the region during Soviet times but became one of a number of strategies for survival and later one of the entrepreneurial diversifications of income generating strategies. Farmers had to become entrepreneurial and diversify their income to overcome the problems encountered with farm insolvency due to the neoliberalization of the economy. However, as farmers were not part of any organized groups they needed to legitimate their illegal activity. I argue that this was possible through claiming that they had a right to subsistence and right to protection from the state, which was denied to them follwoing the collapse of Soviet Union. My case study also demonstrates that cases of corruption among elites deepened the distrust of the state, and lack of governance of drug production by law enforcement contributed further to the legitimation of illegal hashish production. The moral economy of hashish production would not be possible without adopting some informal control mechanisms to drug producers. I also argue that due to local demands to be part of the community, hashish is also used as a source of support. My findings provide detailed discussion of the use of drug money in enriching and maintaining the social community. Overall, this ethnographic study of hashish production in one of the regions of Kyrgyzstan provides rich details of how illegal hashish economy contributes to the legal agricultural economy and culture in the post-Soviet region

Expressivity and Complexity of MongoDB Queries

In this paper, we consider MongoDB, a widely adopted but not formally understood database system managing JSON documents and equipped with a powerful query mechanism, called the aggregation framework. We provide a clean formal abstraction of this query language, which we call MQuery. We study the expressivity of MQuery, showing the equivalence of its well-typed fragment with nested relational algebra. We further investigate the computational complexity of significant fragments of it, obtaining several (tight) bounds in combined complexity, which range from LogSpace to alternating exponential-time with a polynomial number of alternations