Building efficient and flexible feature-based indices

If database management systems are to play an important role in CAD/CAM technologies, building engineering indices must be a primary task even though it is beyond conventional database practice. Information regarding design semantics or functionalities is often embedded in the geometric description of design objects, and is therefore not directly available for indexing. Presented in this paper is an efficient and flexible indexing mechanism for retrieving design objects that possess similar design features as described by the user. The underlying database is composed of rotational objects represented by constructive solid geometry (CSG). Although domain-specific representation schemes and algorithms are involved, the main objective of this paper is to emphasize the importance of engineering indices and to illustrate the effort required to build as well as to use such indices.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/28912/1/0000749.pd

An efficient and flexible design-retrieval mechanism for CAD/CAM databases.

If database management systems are to play an important role in CAD/CAM technologies, building engineering indices must be a primary task. Information regarding design semantics or functionalities is often embedded in the geometric description of design objects, and is therefore not directly available for indexing. Presented in this dissertation is an efficient and flexible indexing mechanism for retrieving design objects that possess similar design features as described by the user. The underlying database is composed of rotational objects represented by constructive solid geometry (CSG). In order to extract information from CSG for indexing, the proposed mechanism employs the Principal Axis Representation (PAR) scheme for computing geometric properties and the Pattern String (PS) Representation for extracting shape features. Both the PAR and PS schemes are developed in this dissertation to represent rotational objects of a single principal axis. Efficient algorithms that convert CSG into PAR and that convert PAR into PS are also presented. Based on Aho and Corasick's string matching algorithm, extracting features from pattern strings becomes an extremely efficient and flexible task. The retrieval mechanism utilizes these representation schemes and algorithms to build indices off-line and to generate search-key values on-line for retrieval. However, the retrieval mechanism is limited by the geometric coverage of PAR and PS, which deals with single-axis rotational objects only. To further enhance this mechanism, a CSG tree reconstruction technique based on node pairing is developed in order to extend the geometric coverage to multiple-axis rotational objects. A formal technique is developed and a series of theoretical and experimental studies is conducted. The result is an efficient algorithm which pairs nodes with as few duplicated nodes as possible. This node-pairing algorithm can be utilized to reconstruct a CSG tree and cluster CSG nodes of the same axis under a subtree, which is ready to be converted into a PAR or PS representation. As a new research problem beyond the practice of conventional database design, this dissertation research identifies the importance of building engineering indices for CAD/CAM databases and illustrates the effort required to build and use such indices.Ph.D.Computer scienceIndustrial engineeringUniversity of Michiganhttp://deepblue.lib.umich.edu/bitstream/2027.42/162468/1/9013931.pd

An adaptive approximation method to discover frequent itemsets over sliding-window-based data streams

Frequent-pattern discovery in data streams is more challenging than that in traditional databases since several requirements need to be additionally satisfied. For the sliding-window model of data streams, transactions both enter into and leave from the window at each sliding. In this paper, we propose an approximation method for mining frequent itemsets over the sliding window of a data stream. The proposed method could approximate itemsets' counts from the counts of their subsets instead of scanning the transactions for them. By noticing the more dynamic feature of sliding-window model, we have made an effort to devise a promising technique which enables the proposed method to approximate for itemsets adaptively. In addition, another technique which may adjust and correct the approximations is also designed. Empirical results have shown that the performance of proposed method is quite efficient and stable; moreover, the mining result from adaptive approximation (and approximation adjustment) achieves high accuracy. (C) 2011 Elsevier Ltd. All rights reserved

A new CSG tree reconstruction algorithm for feature unification

http://deepblue.lib.umich.edu/bitstream/2027.42/6235/5/bac7165.0001.001.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/6235/4/bac7165.0001.001.tx

PAR : a new representation scheme for rational parts

http://deepblue.lib.umich.edu/bitstream/2027.42/6236/5/bac7170.0001.001.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/6236/4/bac7170.0001.001.tx

A syntactic approach to twig-query matching on XML streams

Query matching on XML streams is challenging work for querying efficiency when the amount of queried stream data is huge and the data can be streamed in continuously. In this paper, the method Syntactic Twig-Query Matching (STQM) is proposed to process queries on an XML stream and return the query results continuously and immediately. STQM matches twig queries on the XML stream in a syntactic manner by using a lexical analyzer and a parser, both of which are built from our lexical-rules and grammar-rules generators according to the user's queries and document schema, respectively. For query matching, the lexical analyzer scans the incoming XML stream and the parser recognizes XML structures for retrieving every twig-query result from the XML stream. Moreover, STQM obtains query results without a post-phase for excluding false positives, which are common in many streaming query methods. Through the experimental results, we found that STQM matches the twig query efficiently and also has good scalability both in the queried data size and the branch degree of the twig query. The proposed method takes less execution time than that of a sequence-based approach, which is widely accepted as a proper solution to the XML stream query. (C) 2011 Elsevier Inc. All rights reserved

A generic simulation model for evaluating concurrency control protocols in native XML database systems

In this paper we propose a generic simulation model, named XSM, with which researchers can construct standard platforms and evaluate their proposed concurrency control protocols for native XDBMSs. The system environment, the performance metrics, and the protocol rules of various types of XML protocols are all considered by the model. To facilitate the implementation of XSM, the state diagrams, the sequence diagrams, the component diagram, and the class diagram of XSM are depicted using UML 2.0 notations. We also show a simulation platform constructed from XSM to fairly and comprehensively evaluate the performance of various XML protocols. (C) 2010 Elsevier B.V. All rights reserved

MINING HYBRID SEQUENTIAL PATTERNS BY HIERARCHICAL MINING TECHNIQUE

Unlike sequential patterns, hybrid sequential patterns display not only the path but also the relationship among transaction items. The information provided by the collection of hybrid sequential patterns is useful in improving the analysis of marketing strategies, such as, browsing web pages, discovering customers' behaviors and so on. The process of mining hybrid sequential patterns in a database, however, becomes Complicated by the huge number of candidate patterns. In this paper, we propose a hierarchical mining technique to deal with this complexity. The unique features of this new technique include: counting hybrid sequential patterns by class, and examining database transactions in a top-down manner. This results in scanning a database, at most, twice. Using the technique, we develop an efficient mining algorithm, and conduct a simulation to study its performance. There are three major contributions in this paper. First, our proposed pattern-class concept provides a new way to count a group of patterns simultaneously. Second, we propose a novel decomposition model to lower the I/O cost in counting patterns from a large database. And third, we prove the correctness of counting patterns in the pattern decomposition model in this paper