MASCARA (ModulAr Semantic CAching fRAmework) towards FPGA Acceleration for IoT Security Monitoring

With the explosive growth of the Internet Of Things (IOTs), emergency security monitoring becomes essential to efficiently manage an enormous amount of information from heterogeneous systems. In concern of increasing the performance for the sequence of online queries on long-term historical data, query caching with semantic organization, called Semantic Query Caching or Semantic Caching (SC), can play a vital role. SC is implemented mostly in software perspective without providing a generic description of modules or cache services in the given context. Hardware acceleration with FPGA opens new research directions to achieve better performance for SC. Hence, our work aims to propose a flexible, adaptable, and tunable ModulAr Semantic CAching fRAmework (MASCARA) towards FPGA acceleration for fast and accurate massive logs processing applications

Handling SQL Nulls with Two-Valued Logic

The design of SQL is based on a three-valued logic (3VL), rather than the familiar Boolean logic with truth values true and false, to accommodate the additional truth value unknown for handling nulls. It is viewed as indispensable for SQL expressiveness, but is at the same time much criticized for leading to unintuitive behavior of queries and thus being a source of programmer mistakes. We show that, contrary to the widely held view, SQL could have been designed based on the standard Boolean logic, without any loss of expressiveness and without giving up nulls. The approach itself follows SQL’s evaluation which only retains tuples for which conditions in the WHERE clause evaluate to true. We show that conflating unknown, resulting from nulls, with false leads to an equally expressive version of SQL that does not use the third truth value. Queries written under the two-valued semantics can be efficiently translated into the standard SQL and thus executed on any existing RDBMS. These results cover the core of the SQL 1999 Standard, including SELECT-FROM-WHERE-GROUP BY-HAVING queries extended with subqueries and IN/EXISTS/ANY/ALL conditions, and recursive queries. We provide two extensions of this result showing that no other way of converting 3VL into Boolean logic, nor any other many-valued logic for treating nulls could have possibly led to a more expressive language. These results not only present small modifications of SQL that eliminate the source of many programmer errors without the need to reimplement database internals, but they also strongly suggest that new query languages for various data models do not have to follow the much criticized SQL’s three-valued approach

Veer: Verifying Equivalence of Workflow Versions in Iterative Data Analytics

Data analytics using GUI-based workflows is an iterative process in which an analyst makes many iterations of changes to refine the workflow, generating a different version at each iteration. In many cases, the result of executing a workflow version is equivalent to a result of a prior executed version. Identifying such equivalence between the execution results of different workflow versions is important for optimizing the performance of a workflow by reusing results from a previous run. The size of the workflows and the complexity of their operators often make existing equivalence verifiers (EVs) not able to solve the problem. In this paper, we present "Veer," which leverages the fact that two workflow versions can be very similar except for a few changes. The solution divides the workflow version pair into small parts, called windows, and verifies the equivalence within each window by using an existing EV as a black box. We develop solutions to efficiently generate windows and verify the equivalence within each window. Our thorough experiments on real workflows show that Veer is able to not only verify the equivalence of workflows that cannot be supported by existing EVs but also do the verification efficiently

Foundations of Fuzzy Logic and Semantic Web Languages

This book is the first to combine coverage of fuzzy logic and Semantic Web languages. It provides in-depth insight into fuzzy Semantic Web languages for non-fuzzy set theory and fuzzy logic experts. It also helps researchers of non-Semantic Web languages get a better understanding of the theoretical fundamentals of Semantic Web languages. The first part of the book covers all the theoretical and logical aspects of classical (two-valued) Semantic Web languages. The second part explains how to generalize these languages to cope with fuzzy set theory and fuzzy logic

Foundations of Fuzzy Logic and Semantic Web Languages

This book is the first to combine coverage of fuzzy logic and Semantic Web languages. It provides in-depth insight into fuzzy Semantic Web languages for non-fuzzy set theory and fuzzy logic experts. It also helps researchers of non-Semantic Web languages get a better understanding of the theoretical fundamentals of Semantic Web languages. The first part of the book covers all the theoretical and logical aspects of classical (two-valued) Semantic Web languages. The second part explains how to generalize these languages to cope with fuzzy set theory and fuzzy logic

Complex Event Processing with XChangeEQ

The emergence of event-driven architectures, automation of business processes, drastic cost-reductions in sensor technology, and a growing need to monitor IT systems (as well as other systems) due to legal, contractual, or operational considerations lead to an increasing generation of events. This development is accompanied by a growing demand for managing and processing events in an automated and systematic way. Complex Event Processing (CEP) encompasses the (automatable) tasks involved in making sense of all events in a system by deriving higher-level knowledge from lower-level events while the events occur, i.e., in a timely, online fashion and permanently. At the core of CEP are queries which monitor streams of "simple" events for so-called complex events, that is, events or situations that manifest themselves in certain combinations of several events occurring (or not occurring) over time and that cannot be detected from looking only at single events. Querying events is fundamentally different from traditional querying and reasoning with database or Web data, since event queries are standing queries that are evaluated permanently over time against incoming streams of event data. In order to express complex events that are of interest to a particular application or user in a convenient, concise, cost-effective and maintainable manner, special purpose Event Query Languages (EQLs) are needed. This thesis investigates practical and theoretical issues related to querying complex events, covering the spectrum from language design over declarative semantics to operational semantics for incremental query evaluation. Its central topic is the development of the high-level event query language XChangeEQ. In contrast to previous data stream and event query languages, XChangeEQ's language design recognizes the four querying dimensions of data extractions, event composition, temporal relationships, and, for non-monotonic queries involving negation or aggregation, event accumulation. XChangeEQ deals with complex structured data in event messages, thus addressing the need to query events communicated in XML formats over the Web. It supports deductive rules as an abstraction and reasoning mechanism for events. To achieve a full coverage of the four querying dimensions, it builds upon a separation of concerns of the four querying dimensions, which makes it easy-to-use and highly expressive. A recurrent theme in the formal foundations of XChangeEQ is that, despite the fundamental differences between traditional database queries and event queries, many well-known results from databases and logic programming are, with some importance changes, applicable to event queries. Declarative semantics for XChangeEQ are given as a (Tarski-style) model theory with accompanying fixpoint theory. This approach accounts well for (1) data in events and (2) deductive rules defining new events from existing ones, two aspects often neglected in previous work of semantics of EQLs. For the evaluation of event queries, this work introduces operational semantics based on an extended and tailored form of relational algebra and query plans with materialization points. Materialization points account for storing and maintaining information about those received events that are relevant for, i.e., can contribute to, future query answers, as well as for an incremental evaluation that avoids recomputing certain intermediate results. Efficient state maintenance in incremental evaluation is approached by "differentiating" algebra expressions, i.e., by deriving expressions for computing only the changes to materialization points. Knowing how long an event is relevant is a prerequisite for performing garbage collection during event query evaluation and also of central importance for developing cost-based query planners. To this end, this thesis introduces a notion of relevance of events (to a given query plan) and develops methods for determining temporal relevance, a particularly useful form based on time-related information

Modeling of query languages and applications in code refactoring and code optimization

Проблем садржаности упита један је од фундаменталних проблема у рачунар- ским наукама, иницијално дефинисан за релационе упите. Са растућом популарношћу SPARQL упитног језика, проблем постаје релевантан и актуелан и у овом новом контексту. У тези је представљен оригинални приступ решавању овог проблема заснован на сво- ђењу на задовољивост у логици првог реда. Подржана је садржаност упита узимајући у обзир RDF схему, а разматра се и релација стапања, као слабија форма садржаности. Доказана је сагласност и потпуност предложеног приступа на широком спектру језич- ких конструката. Описана је и његова имплементација, у виду решавача SPECS, чији је кôд јавно доступан. Представљени су резултати детаљне експерименаталне евалуације на релевантним скуповима примера за тестирање који показују да је SPECS ефикасан, и да у поређењу са осталим савременим решавачима истог проблема даје прецизније ре- зултате у краћем времену, уз бољу покривеност језичких конструката. Једна од примена моделовања упитних језика може бити и при рефакторисању апликација које присту- пају базама података. У таквим ситуацијама, врло су честе измене којима се мењају и упити и кôд на језику у коме се они позивају. Такве промене могу сачувати укупну еквивалентност кода, док на нивоу појединачних делова еквивалентност не мора бити одржана. Коришћење алата за аутоматску верификацију еквивалентности рефактори- саног кода може да дâ гаранцију задржавања понашања програма и од суштинског је значаја за поуздан развој софтвера. Са том мотивацијом, у тези се разматра и модело- вање SQL упита у теоријама логике првог реда, којим се омогућава аутоматска провера еквивалентности C/C++ програма са уграђеним SQL-ом, што је и имплементирано у виду јавно доступног алата отвореног кода SQLAV.The query containment problem is a very important computer science problem, originally defined for relational queries. With the growing popularity of the SPARQL query language, it became relevant and important in this new context, too. This thesis introduces a new approach for solving this problem, based on a reduction to satisfiability in first order logic. The approach covers containment under RDF SCHEMA entailment regime, and it can deal with the subsumption relation, as a weaker form of containment. The thesis proves soundness and completeness of the approach for a wide range of language constructs. It also describes an implementation of the approach as an open source solver SPECS. The experimental evaluation on relevant benchmarks shows that SPECS is efficient and comparing to state-of-the-art solvers, it gives more precise results in a shorter amount of time, while supporting a larger fragment of SPARQL constructs. An application of query language modeling can be useful also along refactoring of database driven applications, where simultaneous changes that include both a query and a host language code are very common. These changes can preserve the overall equivalence, without preserving equivalence of these two parts considered separately. Because of the ability to guarantee the absence of differences in behavior between two versions of the code, tools that automatically verify code equivalence have great benefits for reliable software development. With this motivation, a custom first-order logic modeling of SQL queries is developed and described in the thesis. It enables an automated approach for reasoning about equivalence of C/C++ programs with embedded SQL. The approach is implemented within a publicly available and open source framework SQLAV