29028846
Reuse or Never Reuse the Deleted Labels in XML Query Processing Based on Labeling Schemes
To facilitate the XML query processing, several kinds of labeling schemes have been proposed. Based on the labeling schemes, the ancestor-descendant and parent-child relationships in XML queries can be quickly determined without accessing the original XML file. Recently, more researches are focused on how to update the labels when nodes are inserted into the XML. However how to process the deleted labels are not discussed previously. We think that the deleted labels can be processed in two different directions: (1) reuse all the deleted labels to control the label size increasing speed and improve the query performance; (2) never reuse the deleted labels to query different versions of the XML data based on labeling schemes. In this paper, we firstly introduce our previous work, called QED, which can completely avoid the re-labeling in XML updates. Secondly based on QED we propose a new algorithm, called Reuse, which can reuse all the deleted labels to control the label size increasing speed; meanwhile the Reuse algorithm can completely avoid the re-labeling also. Thirdly to query different versions of the XML data, we propose another new algorithm, called NeverReuse, which is the only approach that never reuses any deleted labels. Extensive experimental results show that the algorithms proposed in this paper can control the label size increasing speed when reusing all the deleted labels, and is the only approach to query different versions of the XML data based on labeling schemes.
5215475
QED: a novel quaternary encoding to completely avoid re-labeling in XML updates
The method of assigning labels to the nodes of the XML tree is called a labeling scheme. Based on the labels only, both ordered and un-ordered queries can be processed without accessing the original XML file. One more important point for the labeling scheme is the label update cost in inserting or deleting a node into or from the XML tree. All the current labeling schemes have high update cost, therefore in this paper we propose a novel quaternary encoding approach for the labeling schemes. Based on this encoding approach, we need not re-label any existing nodes when the update is performed. Extensive experimental results on the XML datasets illustrate that our QED works much better than the existing labeling schemes on the label updates when considering either the number of nodes or the time for re-labeling.
1216815
Efficient Processing of Updates in Dynamic XML Data
It is important to process the updates when nodes are inserted into or deleted from the XML tree. All the existing labeling schemes have high update cost, thus in this paper we propose a novel Compact Dynamic Binary String (CDBS) encoding to efficiently process the updates. CDBS has two important properties which form the foundations of this paper: (1) CDBS supports that codes can be inserted between any two consecutive CDBS codes with the orders kept and without re-encoding the existing codes; (2) CDBS is orthogonal to specific labeling schemes, thus it can be applied broadly to different labeling schemes or other applications to efficiently process the updates. We report our experimental results to show that our CDBS is superior to previous approaches to process updates in terms of the number of nodes to re-label and the time for updating.
139092767
An Improved Prefix Labeling Scheme: A Binary String Approach for Dynamic Ordered XML
A number of labeling schemes have been designed to facilitate the query of XML, based on which the ancestor-descendant relationship between any two nodes can be determined quickly. Another important feature of XML is that the elements in XML are intrinsically ordered. However the label update cost is high based on the present labeling schemes. They have to re-label the existing nodes or re-calculate some values when inserting an order-sensitive element. Thus it is important to design a scheme that supports order-sensitive queries, yet it has low label update cost. In this paper, we design a binary string prefix scheme which supports order-sensitive update without any re-labeling or re-calculation. Theoretical analysis and experimental results also show that this scheme is compact compared to the existing dynamic labeling schemes, and it provides efficient support to both ordered and un-ordered queries.
16587000
OWL-Based Semantic Conflicts Detection and Resolution for Data Interoperability
Ontology provides sharing knowledge among different data sources which will help to clarify the semantics of information. OWL is being promoted as a standard for web ontology language, thus in the future a considerable number of ontologies will be created based on OWL. Therefore automatically detecting semantic conflicts based on OWL will greatly expedite the step to achieve semantic interoperability, and will greatly reduce the manual work to detect semantic conflicts. In this paper, we summarize seven cases based on OWL in which semantic conflicts are easily to be encountered, and for each case, we give a rule to resolve the conflict. Via a series of examples, we show how this method works. Based on the seven cases, we propose a semantic conflicts detection and resolution algorithm. This aims at providing a semi-automatic method for semantic uniform data interoperability and integration.
22643655
On reducing redundancy and improving efficiency of XML labeling schemes
The basic relationships to be determined in XML query processing are ancestor-descendant (A-D), parent-child (P-C), sibling and ordering relationships. The containment labeling scheme can determine the A-D, P-C and ordering relationships fast, but it is very expensive in determining the sibling relationship. The prefix labeling scheme can determine all the four basic relationships fast if the XML tree is shallow. However, if the XML tree is deep, the prefix scheme is inefficient since the prefix is long. Furthermore, the prefix label is repeated by all the siblings (only the self labels of these siblings are different). Thus in this paper, we propose the P-Containment and P-Prefix schemes which can determine all the four basic relationships faster no matter what the XML structure is; meanwhile P-Prefix can reduce the redundancies in the prefix labeling scheme.
17572048
Supporting ad-hoc ranking aggregates
This paper presents a principled framework for efficient processing of ad-hoc top-k (ranking) aggregate queries, which provide the k groups with the highest aggregates as results. Essential support of such queries is lacking in current systems, which process the queries in a naïve materialize-group-sort scheme that can be prohibitively inefficient. Our framework is based on three fundamental principles. The Upper-Bound Principle dictates the requirements of early pruning, and the Group-Ranking and Tuple-Ranking Principles dictate group-ordering and tuple-ordering requirements. They together guide the query processor toward a provably optimal tuple schedule for aggregate query processing. We propose a new execution framework to apply the principles and requirements. We address the challenges in realizing the framework and implementing new query operators, enabling efficient group-aware and rank-aware query plans. The experimental study validates our framework by demonstrating orders of magnitude performance improvement in the new query plans, compared with the traditional plans.
2062689
Optimizing Large Join Queries in Mediation Systems
In data integration systems, queries posed to a mediator need to be translated into a sequence of queries to the underlying data sources. In a heterogeneous environment, with sources of diverse and limited query capabilities, not all the translations are feasible. In this paper, we study the problem of finding feasible and efficient query plans for mediator systems. We consider conjunctive queries on mediators and model the source capabilities through attribute-binding adornments. We use a simple cost model that focuses on the major costs in mediation systems, those involved with sending queries to sources and getting answers back. Under this metric, we develop two algorithms for source query sequencing - one based on a simple greedy strategy and another based on a partitioning scheme. The first algorithm produces optimal plans in some scenarios, and we show a linear bound on its worst case performance when it misses optimal plans. The second algorithm generates optimal plans in more scenarios, while having no bound on the margin by which it misses the optimal plans. We also report on the results of the experiments that study the performance of the two algorithms.
17174915
Diagnosis of tunneling opens
This paper resolves two issues regarding diagnosis of tunneling opens: efficient screening and accurate localization. In the first part, a test pattern selection and sorting algorithm is presented. It is shown that the presented algorithm saves I/sub DDQ/(t) test time without impacting on its effectiveness. The second part of this paper presents a locating algorithm which combines both VLV and I/sub DDQ/(t) test results. This technique is shown to be able to accurately locate the tunneling opens with higher resolution than commercial single stuck-at fault diagnosis tool.
15797731
A Novel Indexing Approach for Efficient and Fast Similarity Search of Captured Motions
Indexing of motion data is important for quickly searching similar motions for sign language recognition and gait analysis and rehabilitation. This paper proposes a simple and efficient tree structure for indexing motion data with dozens of attributes. Feature vectors are extracted for indexing by using singular value decomposition (SVD) properties of motion data matrices. By having similar motions with large variations indexed together, searching for similar motions of a query needs only one node traversal at each tree level, and only one feature needs to be considered at one tree level. Experiments show that the majority of irrelevant motions can be pruned while retrieving all similar motions, and one traversal of the indexing tree takes only several microseconds with the existence of motion variations.
18972651
User preferences, information transactions and location-based services: A study of urban pedestrian wayfinding
Though research into location-based services (LBS) is being carried out across a number of disciplines, user aspects of LBS remains a cross-cutting theme. In this paper, the research focuses on investigating the user information requirements from LBS at individual level, with emphasis on the interactive nature of information transactions between environments, individuals and mobile devices. Based on a proposed conceptual model, urban pedestrian wayfinding experiments have been implemented in an immersive virtual reality test environment. Automated and semi-automated methods of data collection have allowed an integrated picture of participant behaviour and information preferences to be constructed and analysed. The results of this study show that there are clear user preferences in information requirements in completing wayfinding tasks. However, changes in user preferences during the wayfinding tasks do occur in response to levels of confidence, different spatial layouts and the wayfinding situations individuals encounter. The outcomes indicate that the proposed conceptual interaction model and adopted implementation approach assist in understanding user behaviour and information preferences for LBS.