Search

As XML usage grows for both data-centric and document-centric applications, introducing native support for XML data in relational databases brings significant benefits. It provides a more mature platform for the XML data model and serves as the basis for interoperability between relational and XML data. Whereas query processing on XML data shredded into one or more relational tables is well understood, it provides limited support for the XML data model. XML data can be persisted as a byte sequence (BLOB) in columns of tables to support the XML model more faithfully. This introduces new challenges for query processing such as the ability to index the XML blob for good query performance. This paper reports novel techniques for indexing XML data in the upcoming version of Microsoft® SQL ServerTM, and how it ties into the relational framework for query processing.

Most of the work on XML query and search has stemmed from the publishing and database communities, mostly for the needs of business applications. Recently, the Information Retrieval community began investigating the XML search issue to answer information discovery needs. Following this trend, we present here an approach where information needs can be expressed in an approximate manner as pieces of XML documents or "XML fragments" of the same nature as the documents that are being searched. We present an extension of the vector space model for searching XML collections via XML fragments and ranking results by relevance. We describe how we have extended a full-text search engine to comply with this model. The value of the proposed method is demonstrated by the relative high precision of our system, which was among the top performers in the recent INEX workshop. Our results indicate that certain queries are more appropriate than others for the extended vector space model. Specifically, queries with relatively specific contexts but vague information needs are best situated to reap the benefit of this model. Finally our results show that one method may not fit all types of queries and that it could be worthwhile to use different solutions for different applications.

Currently there are many commercial XML data management systems available. Most of these products are based on the traditional database management systems such as relational/object-oriented systems. Recently, some native XML data management systems have been introduced. However, the previous XML repository structures are based on disk, it is inefficient to support real-time and mobile applications effectively. Hence, in this paper, we design a main memory-based XML repository structure to support real-time applications efficiently. To store and manage XML documents in native format, we design a logical data model for XML documents. And we design a repository structure at the physical level based on this logical model and finally, implement the proposed repository structure.

As Web applications manipulate an increasing amount of XML, there is a growing interest in storing XML data in relational databases. Due to the mismatch between the complexity of XML's tree structure and the simplicity of flat relational tables, there are many ways to store the same document in an RDBMS, and a number of heuristic techniques have been proposed. These techniques typically define fixed mappings and do not take application characteristics into account. However, a fixed mapping is unlikely to work well for all possible applications. In contrast, LegoDB is a cost-based XML storage mapping engine that explores a space of possible XML-to-relational mappings and selects the best mapping for a given application. LegoDB leverages current XML and relational technologies: (1) it models the target application with an XML Schema, XML data statistics, and an XQuery workload; (2) the space of configurations is generated through XML-Schema rewritings; and (3) the best among the derived configurations is selected using cost estimates obtained through a standard relational optimizer. We describe the LegoDB storage engine and provide experimental results that demonstrate the effectiveness of this approach.

Modern digital consumer devices are now enabled to handle certain types of XML data. In many cases, such data are periodically downloaded from remote via some network. In this paper, methods of storing and querying of XML data within digital devices are considered where relatively large scale XML data are downloaded in packetized formats for secure and efficient delivery from the senders to the receiving devices. Specifically, the downloaded XML fragments are natively organized by the fragment-oriented data structures and the supporting indexes both of which can be easily implemented on top of a lightweight relational storage. The proposed design provides efficient search and retrieval of XML data as well as dynamic update and versioning within resource-limited digital devices.

This paper addresses the issue of semantically clustering the increasing number of the schemaless XML documents. In our approach, each document in a document collection is firstly represented by a macro-path sequence. Secondly, the similarity matrix for a document collection is constructed by computing the similarity value among these macro-path sequences. Finally, the desired clusters are constructed by utilizing the hierarchical clustering technique. Experimental results are also shown in this paper.

Various XML instances from different data sources can model the same object of the real world. Query processing or view definition over these sources demands instance integration. In this context, integration means to identify which data instances represent the same object of the real world, as well as to solve ambiguities of representation of this object. The entity identification problem in XML is more complex than in structured databases. XML data, as originally considered, necessarily do not have the identification notion of primary key or object identifier. Thus, it is necessary the adoption of a mechanism that identifies the instances at the moment of data integration. This paper presents a proposal for identifiers attribution to XML instances, based on the use of Skolem functions and XPath recommendation, as proposed by W3C.

In this paper, we discuss the XEDY system for storing DTD-conscious\/ XML data in a standard relational databases management system. For this, we propose a database schema for storing any set of XML documents accompanied by DTDs. We demonstrate that our approach reduces number of join operations while executing queries. User will be able to perform query on the XML data stored in XEDY and also be able to extract the XML data stored in the RDBMS without loss of information. We evaluate the performance of the proposed system in term of insertion and extraction speed and database storage requirement.

Namespace and package commands implement two different concepts that work together to make it easier to write reusable, modular, and easily maintained code. The namespace command provides encapsulation support for developing modular code. The package command provides tools for organizing code modules into libraries. Namespace scopes have some of the characteristics of the global scope and some characteristics of a procedure local scope. A namespace can be viewed as a global scope within a scope and it can contain other namespaces, creating a tree structure similar to a file system. A script can publish the procedures within a namespace it considers public, with the namespace export command. The namespace command has many subcommands, but most Tcl applications will only use the eval, export, and import commands. A namespace can be populated with procedures and data either in a single namespace eval command or in multiple invocations of the command. The package provides command changes a simple set of procedures to a Tcl package. This command defines a set of procedures as part of a package identified by the package name and a revision number. These procedures can be indexed and can be loaded automatically when they are needed by another script. The Tcl package command provides a framework for: finding and loading the code modules a script requires, tracking the version numbers of packages and loading the proper version, and defining whether the file to be loaded is a script file or shared library/DLL.

Publisher Summary This chapter addresses the question who needs XML database and for what purposes. Some applications use XML as a convenient way to share information, whereas others use XML as a solution for long-term storage. Regardless, the common denominator for all applications is the need for a standard repository infrastructure to speed up the development process, improve quality and stability, and reduce development costs. The software market has responded with different solutions to this need. Some solutions rely on extended relational or object-oriented database systems, and others on enhanced information retrieval systems. Still others use the latest and greatest native XML databases.

Relational database systems are well-suited as a platform for data-centric XML processing. Data-centric applications process regularly structured XML documents using precise predicates. However, these approaches come too short when XML applications also require document-centric processing, i.e., processing of less rigidly structured documents using vague predicates in the sense of information retrieval. The PowerDB-XML project at ETH Zurich aims to address this drawback and to cover both these types of XML applications on a single platform. In this paper, we investigate the requirements of document-centric XML processing and propose to refine state-of-the-art retrieval models for unstructured flat document such that they meet the flexibility of the XML format. To do so, we rely on so-called query-specific statistics computed dynamically at query runtime to reflect the query scope. Moreover, we show that document-centric XML processing is efficiently feasible using relational database systems for storage management and standard SQL. This allows us to combine document-centric processing with data-centric XML-to-database mappings. Our XML engine named PowerDB-XML therefore supports the full range of XML applications on the same integrated platform.

This chapter explores Extensible Markup Language (XML) and the XML-related tools that WebSphere Studio Application Developer (WSAD) 5.0 provides. Although you should be familiar with Java 2 Enterprise Edition (J2EE) technology (and with XML in particular), this chapter introduces some important concepts of XML. Specifically, it dedicates several sections to the XML namespace.

Given the fact that relational and object-relational databases are the most widely used technology for storing data and that XML is the standard format used in electronic data interchange, the process of converting relational data to XML documents is one that occurs frequently. The problem that we address in this paper is an important one related to this process. If we convert a relation to an XML document, under what circumstances is the XML document redundancy free? In some allied work we formally defined functional dependencies in XML (XFDs) and, based on this definition, formally defined redundancy in an XML document. We then introduced a normal form for an XML document (XNF) and showed that it is a necessary and sufficient condition for the elimination of redundancy. In this paper we address the problem of determining what class of mappings map a relation in BCNF to an XML document in XNF. The class of mappings we consider is very general and allows arbitrary nesting of the original flat relation. Our main result establishes a necessary and sufficient condition on the DTD induced by the mapping for it to be in XNF.

With the advent of XML, it is becoming the de facto standard required by the Web applications. To facilitate path expression processing, we propose an index structure adopted in our native XML database system Orient-X. Our index is constructed by utilizing DTD to get paths that will appear in the XML documents. It represents structural summary of XML data collection conforming to certain DTD, so we can process any label path query without accessing original data. In addition, it is integrated with value indexes. Preliminary experiments show quite promising results.

With the rapidly increasing popularity of XML for data representation, there is a lot of interest in query processing over data that conforms to a labeled-tree data model. A variety of languages have been proposed for this purpose, all of which can be viewed as consisting of a pattern language and construction expressions. Since the data objects are typically trees, tree pattern matching is the central issue. The idea behind evaluating tree pattern queries, sometimes called twig queries, is to find all the ways of embedding the pattern in the data. Because this lies at the core of most languages for processing XML data, efficient evaluation techniques for these languages require appropriate indexing structures.

XML is rapidly evolving towards the standard for data integration and exchange over the Internet and within intranets, covering the complete spectrum from largely unstructured, ad hoc documents to highly structured, schematic data. However, established XML query languages like XML-QL [96] or XQuery [34] cannot cope with the rapid growth of information in open environments such as the Web or intranets of large corporations, as they are bound to boolean retrieval and do not provide any relevance ranking for the (typically numerous) results. Recent approaches such as XIRQL [128] or our own system XXL [295, 296] that are driven by techniques from information retrieval overcome the latter problem by considering the relevance of each potential hit for the query and returning the results in a ranked order, using similarity measures like the cosine measure. But they are still tied to keyword queries, which is no longer appropriate for highly heterogeneous XML data from different sources, as it is the case in the Web or in large intranets.

XML is rapidly becoming one of the most adopted standard for information representation and interchange over the Internet. With the proliferation of mobile devices of communication such as palmtop computers in recent years, there has been growing numbers of web applications that generate tremendous amount of XML data transmitted via the Internet. We therefore need to investigate an effective means to handle such ever-growing XML data in various merging activities such as aggregation, accumulation or updating, in addition to storing and querying XML data. Previously, we recognized that FDs are an important and effective means to achieve consistent XML data merging, which we restricted data consistency for leaf nodes in an XML data tree. In this paper we further extend FDs to be satisfied in an XML document by comparing subtrees in a specified context of an XML tree. Given an XML tree T and a set of FDs F defined over a set of given path expressions, called targeted functional path expressions, we tackle the problem of repairing the inconsistency with respect to F in the most concise merged format of T.

XML is an important format of information exchange and representation. One of its features is that it has tag representing semantics. Based on this feature, an extensive aggregation of operation of XML data, Xaggregation, is represented in this paper. Xaggregation permits XPath expression decorating dimension property and measure property. With Xaggregation, statistics of XML data becomes more flexible with function of aggregating heterogeneous data and hierarchy data along some path of XML. Xaggregation could be embedded in query language of XML such as XQuery. In this paper, the definition of Xaggregation is presented, as well as the semantics and application of it. Implementation of Xaggregation based on native XML database with XML as tree structure is also designed.

While providing syntactic flexibility, XML provides little semantic content and so the study of integrity constraints in XML plays an important role in helping to improve the semantic expressiveness of XML. Functional dependencies (FDs) and multivalued dependencies (MVDs) play a fundamental role in relational databases where they provide semantics for the data and at the same time are the foundation for database design. Since XML documents are closely coupled with relational databases in that XML documents are typically exported and imported from relational databases, the study of FDs and MVDs in XML is of fundamental significance in XML research. In this paper we define multivalued dependencies in XML (XMVDs). We then propose a normal form for XML documents in the presence of XMVDs and justify our normal form by showing that it ensures the elimination of redundancy.

An XML document search method which expands XML query through conceptual structuring and association on intra/inter-ontology is proposed. The method can filter out semantic information from various XML documents and can be effective for a large application.

XML is rapidly emerging on the World Wide Web as a standard for representing and exchanging data. It is critical to have efficient mechanisms to store and query XML documents to exploit the full power of this new technology. While one approach is to develop native XML repositories that support XML data models and query languages directly, the other approach is to take advantage of the mature technologies that are provided by current relational or object-relational DBMSs. There is active research along both approaches and it is still not clear which one is better than the other. We continue our effort on the second approach. In particular, we have developed an efficient algorithm which takes an XML DTD as input and produces a relational schema as output for storing and querying XML documents conforming to the input DTD. Our algorithm features several significant improvements over the shared-inlining algorithm including overcoming its incompleteness, eliminating redundancies caused by shared elements, performing optimizations and enhancing efficiency.

XML allows users to define elements using arbitrary words and organize them in a nested structure. These features of XML offer both challenges and opportunities in information retrieval, document management, and data mining. In this paper, we propose a new methodology for preparing XML documents for quantitative determination of similarity between XML documents by taking into account XML semantics (i.e., meanings of the elements and nested structures of XML documents). Accurate quantitative determination of similarity between XML documents provides an important basis for a variety of applications of XML document mining and processing. Experiments with XML documents show that our methodology provides a 50-100% improvement in determining similarity over the traditional vector-space model that considers only term-frequency and 100% accuracy in identifying the category of each document from an on-line bookstore.

In this paper an information system WEBIS is be described that updates its data using specific web-pages. The problem that the structure of HTML-pages can be unexpectedly restructured has been solved by using a controlled transformation into XML and storing XML-documents for data exploitation into an XML repository.

At the forefront of interoperability using XML in an Internet environment is the issue of semantic trans-lation; that is, the ability to properly interpret the elements, attributes, and values contained in an XML file. In many cases, specific domains have standardized the way data are represented in XML. When this does not occur, some type of mediation is required to interpret XML formatted data that does not adhere to pre-defined semantics. The prototype X-Map was developed to investigate what is required to mediate semantic interoperability between heterogeneous domains. An essential component of this system is structural analysis of data representations in the respective domains. When mediating XML data between similar but non-identical domains, we cannot rely solely on semantic similarities of tags and/or the data content of elements to establish associations between related elements, especially over the Internet. To complement these discovered associations one can attempt to build on relationships based on the respective domain structures and the position and relationships of evaluated elements within those structures. For this purpose, the domains are represented as hierarchical trees in XML syntax; a more general solution handles arbitrary graphs. A structural analysis algorithm builds on associations discovered by other analysis, using these associations to aid in discovering further links that could not have been discovered by purely static examination of the elements and their aggregate content. A number of methodologies are presented by which the algorithm maximizes the number of relevant mappings or associations derived from the XML structures. The paper concludes with comparative results obtained using these three methodologies.

XML permits repeated and missing sub-elements, and missing attributes. We discuss the consequent implications on grouping, both with respect to specification and with respect to implementation. The techniques described here have been implemented in the TIMBER native XML database system being developed at the University of Michigan.

Several guest books are already available online for download, but most require either a Microsoft Access database or an SQL Server database for storing the guest book entries and other information pertinent to that guestbook. Even though System.Data is viewed more or less as a method of working with traditional database connections, such as a SQL database or an Access database, it can also work with XML data, provided the XML has an inline schema that it can match the data against. XML and ASP.NET can work together in a variety of ways: from simple reading and writing, to proper design and look. Using a combination of both the System.Data namespace and the ASP server objects, a single-line parsing.aspx page or a more robust page with tables, rows, columns, and different colors and graphics can be created. In order to achieve the best performance available, the System.Data namespace requires an inline schema within the XML file, which the System.Data namespace can reference against, when reading or writing XML. ASP server objects themselves as very flexible in that they can be standalone and provide an area to insert inline ASPX code.

In the previous chapter, I took you on a brief tour of the facilities available in the System.Xml namespace. Microsoft has been moving us toward XML for messaging, storage, and general formatting of sundry lumps of data for some years now, mainly through their MSXML COM libraries. With System.Xml they’ve taken a massive step beyond even this, not only implementing a fully DOM-compliant set of classes and methods in the System.Xml namespace, but also integrating XML itself with almost every aspect of application development using.NET.

Query languages for XML such as XPath or XQuery support Boolean retrieval: a query result is a (possibly restructured) subset of XML elements or entire documents that satisfy the search conditions of the query. This search paradigm works for highly schematic XML data collections such as electronic catalogs. However, for searching information in open environments such as the Web or intranets of large corporations, ranked retrieval is more appropriate: a query result is a rank list of XML elements in descending order of (estimated) relevance. Web search engines, which are based on the ranked retrieval paradigm, do, however, not consider the additional information and rich annotations provided by the structure of XML documents and their element names. This paper presents the XXL search engine that supports relevance ranking on XML data. XXL is particularly geared for path queries with wildcards that can span multiple XML collections and contain both exact-match as well as semantic-similarity search conditions. In addition, ontological information and suitable index structures are used to improve the search efficiency and effectiveness. XXL is fully implemented as a suite of Java servlets. Experiments with a variety of structurally diverse XML data demonstrate the efficiency of the XXL search engine and underline its effectiveness for ranked retrieval.

The common feature of the XML query languages is the use of path expressions to query XML data. To speed up the processing of path expression queries, it is important to be able to quickly determine ancestor-descendant relationship between any pair of nodes in the hierarchy of XML data. At the same time, keyword search is also important to query XML data with a regular structure, if the user does not know the structure or only knows the structure partially. In this paper, we propose a new approach about storing and querying XML data in the RDBMS basing on the idea of the numbering schema and the inverted list. Our approach allows us to quickly determine ancestor-descendant relationship between any pair of nodes in the hierarchy of XML data, which is particularly, highly effective for the searching paths that are very long or unknown. Examples have demonstrated that our approach can effectively supports both query powers in XQuery and keyword searches. Our approach is flexible enough to support XML documents both with schema and without schema, and applications both retrieval and update.

In the proposed data model for XML databases, an XML element is directly represented as a ground (variable-free) XML expression--a generalization of an XML element by incorporation of variables for representation of implicit information and enhancement of its expressive power--while a collection of XML documents as a set of ground expressions, each describing an XML element in the documents. Relationships among elements in the collection as well as integrity constraints are formalized as XML clauses. An XML database, consisting of: (i) a document collection (or an extensional database), (ii) a set of relationships (or an intensional database) and (iii) a set of integrity constraints, is therefore modeled as an XML declarative description comprising a set of ground XML expressions and XML clauses. Its semantics is a set of ground XML expressions, which are explicitly described by the extensional database or implicitly derived from the intensional database and satisfy all the specified set of constraints.

The rapid advance of the Internet has brought with it a variety of WWW applications. Integration of these WWW applications, which implies development of meta level applications (shortened to meta-applications), is an important research issue. In the Internet context, XML has attracted a great deal of attention and will be used as a standard data format in WWW applications. This paper proposes a scheme to develop meta-applications on top of XML-based WWW applications. Our approach uses an XML query language called X2QL to manipulate XML instances. X2QL features the inclusion of user-defined foreign functions so that we can define functions specific to WWW application integration, such as submitting forms and following hyperlinks. In addition, we propose X2PL, which is an extensible XML processing language. In X2PL, processing flows composed of embedded X2QL queries are specified. This paper also describes an integration example and the development of a prototype system.

For most of the index structures for XML data proposed so far, updating is a problem, because an XML element's coordinates are expressed using absolute values. Due to the structural relationship among the elements in XML documents, we have to re-compute these absolute values if the content of the source data is updated. The reconstruction requires the updating of a large portion of the index files, which causes a serious problem, especially when the XML data content is updated frequently. In this paper, we propose an indexing structure scheme based on the relative region coordinates that can effectively deal with the update problem. The main idea is that we express the coordinates of an XML element based on the region of its parent element. We present an algorithm to construct a tree-structured index in which related coordinates are stored together. In consequence, our indexing scheme requires the updating of only a small portion of the index file.

This paper develops a theoretical framework for modeling and managing XML documents by employment of Declarative Description (DD) theory. In the framework, the definition of an XML element is formally extended by incorporation of variables in order to represent inherent implicit information and enhance its expressive power. An XML document - a set of XML elements - is simply modeled as an XML declarative description which consists of object descriptions, representing XML elements in the document, and relationship descriptions, specifying relationships among the elements as well as integrity constraints. DTDs and complex queries can also be expressed and evaluated.

XML users can make their own document structure and tagsets by freely defining the DTD with their intention. This freedom of defining tagsets and the structures, however, prevents the interchange of an XML document between two applications without knowing the other’s DTD. In this paper, we proposed a method to represent meaning of tags in XML documents using data registries as a semantic sharing environment. The key idea of the method is to attach a data element identifier in data registries to the corresponding tags in XML documents. Based on the method, we designed a converting process for XML documents, which make it possible to exchange XML documents between applications automatically even if they use different DTDs.

Content-oriented XML retrieval systems support access to XML repositories by retrieving, in response to user queries, XML document components (XML elements) instead of whole documents. The retrieved XML elements should not only contain information relevant to the query, but also should be specific to the given query (i.e. do not discuss other irrelevant topics). To score XML elements according to how relevant and specific they are given a query, the content and logical structure of XML documents have been widely used. This thesis aims to examine a new source of evidence deriving from the semantic decomposition of XML documents. We consider that XML documents can be semantically decomposed through the application of a topic segmentation algorithm. Using the semantic decomposition and the logical structure of XML documents, we define the notion of topic shifts in an XML element. We then formalise the number of topic shifts to reflect the element's relevance, and more particularly its specificness, to the given user's query. This thesis investigates the use of topic shifts in content-oriented XML retrieval, which is mainly involved in retrieving information from semi-structured (XML) documents. First, we examine the characteristics of XML elements reflected by their number of topic shifts. Second, we use the number of topic shifts to estimate the relevance of the elements in the collection. Finally, we use topic shifts to provide a focused access to XML documents, which aims to determine not only relevant elements, but those at the right level of granularity. The main contributions of this thesis are the introduction of topic shifts in the context of content-oriented XML retrieval and the extensive evaluation of the ways this evidence can be employed in retrieving XML elements. This thesis demonstrates that topic shifts in XML elements constitute a useful source of evidence for both improving the ranking of XML elements, and determining elements at the right level of granularity in content-oriented XML retrieval. The thesis is available online at http://elham.ashoori.org/publications/phd-thesis.pdf.

In a Grid environment the naming capability allows users to refer to specific data resources in a physical storage system using a high level logical identifier. This logical identifier is typically organized in a file system like structure, a hierarchical tree of names. Storage Resource Manager (SRM) services map the logical identifier to the physical location of data evaluating a set of parameters as the desired quality of services and the VOMS attributes specified in the requests. StoRM is a SRM service developed by INFN and ICTP-EGRID to manage file and space on standard POSIX and high performing parallel and cluster file systems. An upcoming requirement in the Grid data scenario is the orthogonality of the logical name and the physical location of data, in order to refer, with the same identifier, to different copies of data archived in various storage areas with different quality of service. The mapping mechanism proposed in StoRM is based on a XML document that represents the different storage components managed by the service, the storage areas defined by the site administrator, the quality of service they provide and the Virtual Organization that want to use the storage area. An appropriate directory tree is realized in each storage component reflecting the XML schema. In this scenario StoRM is able to identify the physical location of a requested data evaluating the logical identifier and the specified attributes following the XML schema, without querying any database service. This paper presents the namespace schema defined, the different entities represented and the technical details of the StoRM implementation.

In the near future, data on the order of hundreds of Petabytes will be spread in multiple storage systems worldwide dispersed in, potentially, billions of replicated data items. Users, typically, are agnostic about the location of their data and they want to get access by either specifying logical names or using some lookup mechanism. A global namespace is a logical layer that allows the view of data resources independently from the physical location. Usually, the naming scheme is designed to be easily interpreted by humans and it is organized into a purely user-defined directory hierarchy. Within this model, a data resource is uniquely addressed by file name and path. Nevertheless, this hierarchical structures of logical namespace lacks adequate flexibility to manage sophisticated organization of data. In particular the implicit classification of the data item derived from the path is not enough meaningful to classify data objects when different orthogonal dimensions are considered. In this paper we expose an enriched namespace able to support a new type of data access authorization policy based on tags. The tags are organized in well-defined hierarchies providing a simple representation of the domain ontology. Only authorized users can label data resources with different tags taken from the domain tag hierarchies. In this way an overlay of classical hierarchical structure of logical namespace with faceted hierarchical tags provides a semantics classification of data entities. Authorization policies defined in respect of tags are content-aware.

XML has become the de facto standard for data representation and exchange for Web applications, such as digital library, Web service, and electronic business. How to retrieve interesting information from the promising XML data is an active research area. Among techniques in this area, the description of query patterns is a crucial section. This paper reviews the actualities of recent researches on this topic. It classifies the query descriptors into two categories, XML Query type and XML IR type (with three subcategories: XML IR/keyword, XML IR/fragment and XML IR/query), and concludes three popular problems: Twig pattern processing, SLCA (smallest lowest common ancestor) problem, and similarity measuring techniques for retrieved XML fragments. It analyzes the virtue and deficiency of related techniques based on their convenience for common users. And hereby it proposes four issues for further XML querying researches: structural keywords and corresponding structural similarity measuring, wiping off the redundancy in XML data processing between XML Query (including XML IR/query) and XML IR/keyword, theoretical discussion of XML Query and its realization, and the management of peculiar XML data.

One of the challenging issues related to specifying a fine-grained access control on the XML data is how to implement the accessibility map in a compact format with minimum affect on the XML query processing. In this paper, we propose a Compact Bit String Accessibility Map (CBSAM) to implement the accessibility map in a compact format. In order to achieve a secure and efficient XML query processing, the CBSAM is integrated with the region number labeling scheme. The experimental results illustrate that the CBSAM compresses the accessibility map with minimum affect on the XML query processing when the access locality among the XML nodes is high.

Pattern Management Systems and Inductive Databases, are proposed as a new generation of general purpose databases with the aim to manage data mining patterns and work as knowledge bases in support to the deployment of the KDD process. One of the main problems to be solved is the integration between data and patterns and pattern maintenance when data update. Unfortunately, the heterogeneity of the patterns that represent the extracted knowledge and of the different conceptual tools used to find the patterns make difficult this integration in a unique framework. In this paper, we explore the feasibility of using XML as the unifying framework for inductive databases, and present a model, named XDM (XML for Data Mining). We will show the basic features of the model, such as the storage in the same database of both data and patterns. To store patterns, we consider determinant for their interpretation the storage of the pattern derivation process which is described by the concept of statement, based on data mining operators. Some of the statements are automatically generated by the system while maintaining consistence between source and derived data. Furthermore, we show how the use of XML namespaces allows the effective coexistence of different data mining operators and provides extensibility to new operators. Finally, we show that with the use of XML-Schema we are able to define the schema, the state and the integrity constraints of an inductive database.

Using the terminology usual in databases, it is possible to view XML as a language for data modeling. To retrieve XML data from XML databases, several query languages have been proposed. The common feature of such languages is the use of regular path expressions. They enable the user to navigate through arbitrary long paths in XML data. If we considered a path content as a vector of path elements, we would be able to model XML paths as points within a multidimensional vector space. This paper introduces a geometric framework for indexing and querying XML data conceived in this way. In consequence, we can use certain data structures for indexing multidimensional points (objects). We use the UB-tree for indexing the vector spaces and the M-tree for indexing the metric spaces. The data structures for indexing the vector spaces lead rather to exact matching queries while the structures for indexing the metric spaces allow us to provide the similarity queries.

Although a great deal of research work has been done concerning schema changes that deal with basic components of XML Schemas, like element and attribute declarations, simple types, and complex type definitions, the current literature of the XML database field does not include any paper that studies changes of advanced concepts of XML Schemas, like XML namespaces, local (or global) qualified (or unqualified) declarations, and schema definition styles (e.g., Russian Doll, Garden of Eden). In this paper, we study how XML namespace evolution is handled in an XML environment that supports both schema and document versioning. To the best of our knowledge, this is the first work on such a topic. Indeed, we propose a systematic approach that allows specifying changes on XML namespaces defined in XML Schemas, and propagating their effects to underlying XML documents, while maintaining all XML schema and XML instance versions.

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.