553416
Path Constraints in Semistructured Databases
We investigate a class of path constraints that is of interest in connection with both semistructured and structured data. In standard database systems, constraints are typically expressed as part of the schema, but in semistructured data there is no explicit schema and path constraints provide a natural alternative. As with structured data, path constraints on semistructured data express integrity constraints associated with the semantics of data and are important in query optimization. We show that in semistructured databases, despite the simple syntax of the constraints, their associated implication problem is r.e. complete and finite implication problem is co-r.e. complete. However, we establish the decidability of the implication and finite implication problems for several fragments of the path constraint language and demonstrate that these fragments suffice to express important semantic information such as extent constraints, inverse relationships, and local database constraints commonly found in object-oriented databases.
5120213
Interaction between path and type constraints
XML [7], which is emerging as an important standard for data exchange on the World Wide Web, highlights the importance of the semistructured data. Although the XML standard itself does not require any schema or type system, a number of proposals [6, 15, 18] have been developed that roughly correspond to data definition languages. These allow one to constrain the structure of XML data by imposing a schema on it. These and other proposals also advocate the need for integrity constraints, another form of constraints that should, for example, be capable of expressing inclusion constraints and inverse relationships. The latter have recently been studied as path constraints in the context of semistructured data [4, 11]. It is likely that future XML proposals will involve both forms of constraint, and it is therefore appropriate to understand the interaction between them. This paper investigates that interaction. In particular it studies constraint implication problems, which are important both in understanding the semantics of type/constraint systems and in query optimization. A number of results on path constraint implication are established in the presences and absences of type systems. These results demonstrate that adding a type systems may in some cases simplify reasoning about path constraints and in other cases make it harder. For example, it is shown that there is a path constraint implication problem that is decidable in PTIME in the untyped context, but that becomes undecidable when a type system is added. On the other hand, there is an implication problem that is undecidable in the untyped context, but becomes not only decidable in cubic time but also finitely axiomatizable when a type system is imposed. Comments University of Pennsylvania Department of Computer and Information Science Technical Report No. MSCIS-98-16. This technical report is available at ScholarlyCommons: http://repository.upenn.edu/cis_reports/106
8618813
Reasoning about Keys for XML
We study absolute and relative keys for XML, and investigate their associated decision problems. We argue that these keys are important to many forms of hierarchically structured data including XML documents. In contrast to other proposals of keys for XML, these keys can be reasoned about efficiently. We show that the (finite) satisfiability problem for these keys is trivial, and their (finite) implication problem is finitely axiomatizable and decidable in PTIME in the size of keys.
52151587
On XML integrity constraints in the presence of DTDs
The article investigates XML document specifications with DTDs and integrity constraints, such as keys and foreign keys. We study the consistency problem of checking whether a given specification is meaningful: that is, whether there exists an XML document that both conforms to the DTD and satisfies the constraints. We show that DTDs interact with constraints in a highly intricate way and as a result, the consistency problem in general is undecidable. When it comes to unary keys and foreign keys, the consistency problem is shown to be NP-complete. This is done by coding DTDs and integrity constraints with linear constraints on the integers. We consider the variations of the problem (by both restricting and enlarging the class of constraints), and identify a number of tractable cases, as well as a number of additional NP-complete ones. By incorporating negations of constraints, we establish complexity bounds on the implication problem, which is shown to be coNP-complete for unary keys and foreign keys.
6139666
Capturing both types and constraints in data integration
We propose a framework for integrating data from multiple relational sources into an XML document that both conforms to a given DTD and satisfies predefined XML constraints. The framework is based on a specification language, AIG, that extends a DTD by (1) associating element types with semantic attributes (inherited and synthesized, inspired by the corresponding notions from Attribute Grammars), (2) computing these attributes via parameterized SQL queries over multiple data sources, and (3) incorporating XML keys and inclusion constraints. The novelty of AIG consists in semantic attributes and their dependency relations for controlling context-dependent, DTD-directed construction of XML documents, as well as for checking XML constraints in parallel with document-generation. We also present cost-based optimization techniques for efficiently evaluating AIGs, including algorithms for merging queries and for scheduling queries on multiple data sources. This provides a new grammar-based approach for data integration under both syntactic and semantic constraints.
52830913
Interaction between path and type constraints
Path constraints are capable of expressing inclusion and inverse relationships and have proved useful in modeling and querying semistructured data [Abiteboul and Vianu 1999; Buneman et al. 2000]. Types also constrain the structure of data and are commonly found in traditional databases. There has also been work on imposing structure or a type system on semistructured data for storing and querying semistructured data in a traditional database system [Alon et al. 2001; Deutsch et al. 1999a; Florescu and Kossmann 1999; Shanmugasundaram et al. 1999]. One wants to know whether complexity results for reasoning about path constraints established in the untyped (semistructured) context could carry over to traditional databases, and vice versa. It is therefore appropriate to understand the interaction between types and path constraints. In addition, XML [Bray et al. 1998], which may involve both an optional schema (e.g., DTDs or XML Schema [Thompson et al. 2001]) and integrity constraints, highlights the importance of the study of the interaction.This article investigates that interaction. In particular it studies constraint implication problems, which are important both in understanding the semantics of type/constraint systems and in query optimization. It shows that path constraints interact with types in a highly intricate way. For that purpose a number of results on path constraint implication are established in the presence and absence of type systems. These results demonstrate that adding a type system may in some cases simplify reasoning about path constraints and in other cases make it harder. For example, it is shown that there is a path constraint implication problem that is decidable in PTIME in the untyped context, but that becomes undecidable when a type system is added. On the other hand, there is an implication problem that is undecidable in the untyped context, but becomes not only decidable in cubic time but also finitely axiomatizable when a type system is imposed.
11711193
Video-Based Face Recognition Using Bayesian Inference Model
There has been a flurry of works on video sequence-based face recognition in recent years. One of the hard problems in this area is how to effectively combine the facial configuration and temporal dynamics for the recognition task. The proposed method treats this problem in two steps. We first construct several view specific appearance sub-manifolds learned from the training video frames using locally linear embedding (LLE). A general Bayesian inference model is then fit on the recognition task, transforming the complicated maximum likelihood estimation to some elegant distance measures in the learned sub-manifolds. Experimental results on a middle-scale video database demonstrate the effectiveness and flexibility of our proposed method.
234966
Prototyping Digital Libraries Handling Heterogeneous Data Sources - The ETANA-DL Case Study
Information systems used in archaeology have several needs: interoperability among heterogeneous systems, making information available without significant delay, long-term preservation of data, and providing a suite of services to users. In this paper, we show how digital library techniques can be employed to provide solutions to three of these problems. We show this by describing a prototype for an archaeological Digital Library (ETANA-DL). First, ETANA-DL applies and extends the metadata harvesting approach to address some of the needs interoperability, rapid access to data, and data preservation. Second, we show that availability of a pool of components that implement common DL services has helped in rapidly creating the prototype, which was subsequently used for requirements elicitation. However, understanding complex archaeological information systems is a difficult task. Third, therefore, we describe our efforts to model these systems using the 5S framework, and show how the partially developed model has been used to implement complex services helping users carry out key tasks with the integrated data.
5459818
Putting context into schema matching
Attribute-level schema matching has proven to be an important first step in developing mappings for data exchange, integration, restructuring and schema evolution. In this paper we investigate contextual schema matching, in which selection conditions are associated with matches by the schema matching process in order to improve overall match quality. We define a general space of matching techniques, and within this framework we identify a variety of novel, concrete algorithms for contextual schema matching. Furthermore, we show how common schema mapping techniques can be generalized to take more effective advantage of contextual matches, enabling automatic construction of mappings across certain forms of schema heterogeneity. An experimental study examines a wide variety of quality and performance issues. In addition, it demonstrates that contextual schema matching is an effective and practical technique to further automate the definition of complex data transformations.
4216648
Optimizing web search using web click-through data
The performance of web search engines may often deteriorate due to the diversity and noisy information contained within web pages. User click-through data can be used to introduce more accurate description (metadata) for web pages, and to improve the search performance. However, noise and incompleteness, sparseness, and the volatility of web pages and queries are three major challenges for research work on user click-through log mining. In this paper, we propose a novel iterative reinforced algorithm to utilize the user click-through data to improve search performance. The algorithm fully explores the interrelations between queries and web pages, and effectively finds "virtual queries" for web pages and overcomes the challenges discussed above. Experiment results on a large set of MSN click-through log data show a significant improvement on search performance over the naive query log mining algorithm as well as the baseline search engine.
31080635
An integrated two-stage model for intelligent information routing
A recent surge of subscriptions to online news services exemplifies the fact that people and organizations constantly need up-to-date information to stay competitive and make better informed decisions. However, many of these news services often require users to either manually input their profiles or subscribe to existing news channels. This results in lack of intelligence and personalization, and thus make these services less attractive to users. In this paper, an integrated model that combines query expansion with ranking function adaptation for online information routing is proposed and tested using two different large scale corpora. The experimental results show that this new model can deliver much better quality information than existing models.