• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.10 no.7
• /
• pp.3100-3116
• /
• 2016

With the rapid development of urban traffic system and fast increasing of vehicle numbers, the traditional centralized ways to generate the source-destination shortest path in terms of travel time(the optimal path) encounter several problems, such as high server pressure, low query efficiency, roads state without in-time updating. With the widespread use of smart cameras in the urban traffic and surveillance system, this paper maps the optimal path finding problem in the dynamic road network to the shortest routing problem in the smart camera networks. The proposed distributed optimal path generation algorithm employs the delay routing and caching mechanism. Real-time route update is also presented to adapt to the dynamic road network. The test result shows that this algorithm has advantages in both query time and query packet numbers.

• Journal of KIISE:Computing Practices and Letters
• /
• v.16 no.4
• /
• pp.487-491
• /
• 2010

In this paper we propose a new single-query path planning algorithm for working well in high-dimensional configuration space. With the notice of the similarity between single-query algorithms with exploration algorithms, we propose a new path planning algorithm, which applies the Remembering Exploration method, which is one of exploration algorithms, to a path-planning problem by selecting a node from a roadmap, finding out the neighbor nodes from the node, and then inserting the neighbor nodes into the roadmap, recursively. For the performance comparison, we had experiments in 2D and 3D environments and compared the time to find out the path. In the results our algorithm shows the superior performance than other path planning algorithms.

• Journal of KIISE:Databases
• /
• v.28 no.3
• /
• pp.449-457
• /
• 2001

As XML has become an emerging standard for information exchange on the World Wide Web, it has gained attention in database communities to extract information from XML seen as a database model. XML queries are based on regular path queries, which find objects reachable by given regular expressions. To answer many kinds of user queries, it is necessary to evaluate queries that have multiple regular path expressions. However, previous work such as query rewriting and query optimization in the frame work of semistructured data has dealt with a single regular expression. For queries that have multiple regular expressions we suggest a two phase optimizing technique: 1. query rewriting using views by finding the mappings from the view's body to the query's body and 2. for rewritten queries, evaluating each query conjunct and combining them. We show that our rewriting algorithm is sound and our query evaluation technique is more efficient than the previous work on optimizing semistructured queries.

• Journal of KIISE:Databases
• /
• v.31 no.2
• /
• pp.183-194
• /
• 2004

As XML is a do facto standard for a data exchange language, there have been several researches on efficient processing XML queries. The most important thing to consider when processing XML queries is how efficiently we can process path expressions in queries. Some previous works make results by performing a sequence of join operations on all records corresponding to labels in the path expression. Others works check the existence of paths in the query using an RDBMS's string comparison operator and make results by extracting the records corresponding to the paths. In this paper we suggested a new query planning algorithm based on path containment relationships and two join operators supporting the planning algorithm. The join operators use only the records related to the paths in a query as input data, scan them only once, and generate result data using a pipelining mechanism. By analysis and experiments, we confirmed that our techniques(a new query planning algorithm and two join operators) achieved significantly higher performance than other previous works.

• Journal of the Korean Institute of Intelligent Systems
• /
• v.17 no.6
• /
• pp.766-772
• /
• 2007

As XML is widely used, many researches on the XML storage and query processing have been done. But, previous works on path query processing have mainly focused on the storage and retrieval methods for a large XML document or XML documents had a same DTD. Those researches did not efficiently process partial match queries on the differently-structured document set. To resolve the problem, we suggested a new index structure using relational table. The method constructs the $B^+$-tree index using backward label paths instead of forward label paths used in previous researches for storing path information and allows for finding the label paths that match the partial match queries efficiently using it when process the queries.

• Journal of KIISE:Databases
• /
• v.30 no.6
• /
• pp.641-650
• /
• 2003

The eXtensible Markup Language(XML) is emerging as a standard format of data representation and exchange on the Internet. There have been researches about storing and retrieving XML documents using the relational database which has techniques in full growth about large data processing, recovery, concurrency control and so on. Since in previous systems same structure information and fundamental operation are used for processing of various kinds of XML queries, only some specific query can be efficiently processed not all types of query. In this paper, we propose a flexible query processing system. To process query efficiently, the proposed system analyzes regular path expression queries, and uses $\theta$-join operation using region numbering values to check ancestor-descendent relationship and equi-join operation using parent's region start value to check parent-child relationship. Thus, the proposed system processes efficiently XML regular path expressions. From the experimental results, we show that proposed XML query processing system is more efficient than previous systems.

• The KIPS Transactions:PartD
• /
• v.14D no.6
• /
• pp.585-596
• /
• 2007

XML data generally consists of a hierarchical tree-structure which is reflected in mechanisms to store and retrieve XML data. Therefore, when storing XML data in the database, the hierarchical relationships among the XML elements are taken into consideration during the restructuring and storing of the XML data. Also, in order to support the search queries from the user, a mechanism is needed to compute the hierarchical relationship between the element structures specified by the query. The structural join operation is one solution to this problem, and is an efficient computation method for hierarchical relationships in an in database based on the node numbering scheme. However, in order to process a tree structured XML query which contains a complex nested hierarchical relationship it still needs to carry out multiple structural joins and results in another problem of having a high query execution cost. Therefore, in this paper we provide a preprocessing mechanism for effectively reducing the cost of multiple nested structural joins by applying the concept of equivalence classes and suggest a query path reduction algorithm to shorten the path query which consists of a regular expression. The mechanism is especially devised to reduce path queries containing branch nodes. The experimental results show that the proposed algorithm can reduce the time requited for processing the path queries to 1/3 of the original execution time.

• Journal of KIISE:Databases
• /
• v.32 no.6
• /
• pp.641-649
• /
• 2005

As XML is widely used with the development of internet, many researches on the XML storage and query processing have been done Several index techniques have been proposed to efficiently process XML path queries. Recently, structural join has received murk attention as a method to protest the path query. Structural join technique process a path query by identifying the containment relationship of elements. Especially, it has an advantage that we can get the result set by simply comparing related elements only instead of scanning whole document. However during the comparison process, unnecessary elements that are not included in the result set can be scanned. So we propose a new technique, the level structural join. In this technique, we use both the relationship and the level distribution of elements in the path query. Using this technique, we tao improve the performance of query processing only by comparing elements with specific level in the target inverted level.

• The KIPS Transactions:PartD
• /
• v.10D no.4
• /
• pp.621-638
• /
• 2003

As demand of XML documents in the Web increases, Web service applications that manage XML documents as their resource are increasing. The view mechanism for XML data could be considered for effective in query processing in these Web service applications. If the XML query results are maintained as XML materialized views and their relevant XML query is processed using them, the query response time could be reduced. There are two types of processing an in path expression, which is one of the core features of XML query languages, using XML materialized views. One is the type where the complete query result is obtained from the materialized view, and the other is the type where some of the result is obtained from the materialized view and the rest is from the underlying XML documents. In this paper, we investigate the second type. An XML query in this paper is an XML path expression which is one of the core features of XML query languages. We first describe the storage structures of the XML materialized views derived from the underlying XML documents in the XML repository. Then, we propose the algorithms to decompose a given XML query into the subquery against the materialized view and the subquery against the underlying XML documents, and to integrate the results of these subqueries. Through performance evaluation, we figure out the condition under which our XML query decomposition using materialized views is more effective than the conventional processing.

• Journal of Korea Multimedia Society
• /
• v.8 no.6
• /
• pp.729-734
• /
• 2005

In order to access XML data stored in object databases, an efficient index scheme is inevitable. There have been several index schemes that can be used to efficiently retrieve XML data stored In object databases, but they are all the single path indexes that support indexing along a single schema path. Henee, if a query contains an extended path which is denoted by wild character ('*'), a query processor has to examine multiple index objects, resulting in poor performance and inconsistent index management. In this paper, we propose MPI (Multi-Path Index) scheme as a new index scheme that provides the functionality of multiple path indexes more efficiently, while it uses only one index structure. The proposed scheme is easy to manage since it considers the extended path as a logically single schema path. It is also practical since it can be implemented by little modification of the B -tree index structure.