Accuracy-Aware Uncertain Stream Databases

Abstract-Previous work has introduced probability distributions as first-class components in uncertain stream database systems. A lacking element is the fact of how accurate these probability distributions are. This indeed has a profound impact on the accuracy of query results presented to end users. While there is some previous work that studies unreliable intermediate query results in the tuple uncertainty model, to the best of our knowledge, we are the first to consider an uncertain stream database in which accuracy is taken into consideration all the way from the learned distributions based on raw data samples to the query results. We perform an initial study of various components in an accuracy-aware uncertain stream database system, including the representation of accuracy information and how to obtain query results' accuracy. In addition, we propose novel predicates based on hypothesis testing for decision-making using data with limited accuracy. We augment our study with a comprehensive set of experimental evaluations. I. INTRODUCTION Recent research has extended stream databases to handle uncertain data in order to meet the requirements from everincreasing applications in sensor networks and ubiquitous computing (e.g., Where do we obtain the probabilities in the first place? In many applications, probability distributions are learned from observations and measurements, a.k.a. samples. Such applications include sensor networks, ubiquitous computing, and scientific databases. Let us look at an example. Example 1 (accuracy of learned probability distributions). A few projects in both academia and industry (e.g., the CarTel project at MIT [24

Supporting Uncertainty in Standard Database Management Systems

Management of uncertain data in numerous real life applications has attracted the attention of database and artificial intelligent research communities. This has resulted in development of new database management systems (DBMS) in which uncertainty is treated as first class citizens. We follow a different approach in this thesis and develop a system (to which we refer as DBMS with Uncertainty, or UDBMS) which is capable of representing and manipulating uncertain data at the application level on top of a standard relational DBMS. Compared to the first approach which treats uncertainty as its first class citizens, the proposed approach may be considered as “light weight” because it is built upon existing database technologies. As the underlying uncertainty formalism, we consider the Information Source Tracking (IST) method, which is essentially probabilistic. We extend the standard SQL language with uncertainty (to which we refer as USQL), to express queries and transactions in our context. The query processing and optimization techniques are extended accordingly to take into account the presence of uncertainty. To evaluate the performance of UDBMS, we conducted extensive experiments using USQL queries and IST relations obtained by extending the standard TPC-H benchmark queries and generated data. We compare and discuss the two approaches mentioned for uncertainty management. Our results indicate that the performance of the proposed UDBMS is reasonably good when the relations involved can be loaded completely into the main memory