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.
3074232
From XML to Semantic Web
The present web is existing in the HTML and XML formats for persons to browse. Recently there is a trend towards the semantic web where the information can be can be processed and understood by agents. Most of the present research works focus on the translation from HTML to semantic web, but seldom on XML. In this paper, we design a method to translate XML to semantic web. It is known that ontologies play an important role in the semantic web, therefore firstly, we propose a genetic model to organize ontologies, and based on this model, we use three steps, viz. semantic translation, structural translation and schematic translation, to translate XML to semantic web. The aim of the paper is to facilitate the wide use of semantic web.
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.
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.
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.
516020
Efficient Processing of Ordered XML Twig Pattern
Finding all the occurrences of a twig pattern in an XML database is a core operation for efficient evaluation of XML queries. Holistic twig join algorithm has showed its superiority over binary decompose based approach due to efficient reducing intermediate results. The existing holistic join algorithms, however, cannot deal with ordered twig queries. A straightforward approach that first matches the unordered twig queries and then prunes away the undesired answers is obviously not optimal in most cases. In this paper, we study a novel holistic-processing algorithm, called OrderedTJ, for ordered twig queries. We show that OrderedTJ can identify a large query class to guarantee the I/O optimality. Finally, our experiments show the effectiveness, scalability and efficiency of our proposed algorithm.
7959495
Distributed multi-hop scheduling and medium access with delay and throughput constraints
Providing quality of service in random access multi-hop wireless networks requires support from both medium access and packet scheduling algorithms. However, due to the distributed nature of ad hoc networks, nodes may not be able to determine the next packet that would be transmitted in a (hypothetical) centralized and ideal dynamic priority scheduler. In this paper, we develop two mechanisms for QoS communication in multi-hop wireless networks. First, we devise distributed priority scheduling a technique that piggybacks the priority tag of a node's head-of-line packet onto handshake and data packets; e.g., RTS/DATA packets in IEEE 802.11. By monitoring transmitted packets, each node maintains a scheduling table which is used to assess the node's priority level relative to other nodes. We then incorporate this scheduling table into existing IEEE 802.11 priority back-off schemes to approximate the idealized schedule. Second, we observe that congestion, link errors, and the random nature of medium access prohibit an exact realization of the ideal schedule. Consequently, we devise a scheduling scheme termedmulti-hop coordinationso that downstream nodes can increase a packet's relative priority to make up for excessive delays incurred upstream. We next develop a simple analytical model to quantitatively explore these two mechanisms. In the former case, we study the impact of the probability of overhearing another packet's priority index on the scheme's ability to achieve the ideal schedule. In the latter case, we explore the role of multi-hop coordination in increasing the probability that a packet satisfies its end-to-end QoS target. Finally, we perform a set of ns-2 simulations to study the scheme's performance under more realistic conditions.
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.
8663466
Secure XML Publishing without Information Leakage in the Presence of Data Inference
Recent applications are seeing an increasing need that publishing XML documents should meet precise security requirements. In this paper, we consider data-publishing applications where the publisher specifies what information is sensitive and should be protected. We show that if a partial document is published carelessly, users can use common knowledge (e.g., "all patients in the same ward have the same disease") to infer more data, which can cause leakage of sensitive information. The goal is to protect such information in the presence of data inference with common knowledge. We consider common knowledge represented as semantic XML constraints. We formulate the process how users can infer data using three types of common XML constraints. Interestingly, no matter what sequences users follow to infer data, there is a unique, maximal document that contains all possible inferred documents. We develop algorithms for finding a partial document of a given XML document without causing information leakage, while allowing publishing as much data as possible. Our experiments on real data sets show that effect of inference on data security, and how the proposed techniques can prevent such leakage from happening.
701496
Distributed Priority Scheduling and Medium Access in Ad Hoc Networks
Providing Quality-of-Service in random access multi-hop wireless networks requires support from both medium access and packet scheduling algorithms. However, due to the distributed nature of ad hoc networks, nodes may not be able to determine the next packet that would be transmitted in a (hypothetical) centralized and ideal dynamic priority scheduler. In this paper, we develop two mechanisms for QoS communication in multi-hop wireless networks. First, we devise distributed priority scheduling, a technique that piggybacks the priority tag of a node's head-of-line packet onto handshake and data packets; e.g., RTS/DATA packets in IEEE 802.11. By monitoring transmitted packets, each node maintains a scheduling table which is used to assess the node's priority level relative to other nodes. We then incorporate this scheduling table into existing IEEE 802.11 priority backoff schemes to approximate the idealized schedule. Second, we observe that congestion, link errors, and the random nature of medium access prohibit an exact realization of the ideal schedule. Consequently, we devise a scheduling scheme termed multi-hop coordination so that downstream nodes can increase a packet's relative priority to make up for excessive delays incurred upstream. We next develop a simple analytical model to quantitatively explore these two mechanisms. In the former case, we study the impact of the probability of overhearing another packet's priority index on the scheme's ability to achieve the ideal schedule. In the latter case, we explore the role of multi-hop coordination in increasing the probability that a packet satisfies its end-to-end QoS target. Finally, we perform a set of ns-2 simulations to study the scheme's performance under more realistic conditions.
23350440
On Isomorphisms of Connected Cayley Graphs, II
A Cayley graph or digraph Cay(G, S) of a finite groupGis called aCI-graphofGif, for anyT?G, Cay(G, S)?Cay(G, T) if and only ifS?=Tfor some??Aut(G). We study the problem of determining which Cayley graphs and digraphs for a given group are CI-graphs. A finite groupGis called aconnected m-DCI-group(orconnected m-CI-group) if all connected Cayley digraphs (or connected Cayley graphs, respectively) ofGof (out)-valency at most m are CI-graphs. For a groupG, letp(G) be the smallest prime divisor of |G|. It was previously shown that all finite groupsGare connected (p(G)?1)-DCI-groups and all finite groupsGare connected 2(p(G)?1)-CI-groups. In this paper, for every primep, we construct infinitely many finite groupsGsuch thatp(G)=pandGis neither a connectedp-DCI-group nor a connected 2p-CI-group, which provides solutions for several open problems in this area.