元数据互操作技术探讨

首先分析了元数据互操作的三个层次和当前互操作技术的发展趋势；然后以元数据互操作技术OAI为实例分析，简单介绍了OAI的技术框架和OAI协议的主要特点，并给出了元数据采集系统一般的设计方法和需要考虑的问题；最后对元数据互操作的几种技术进行了效益分析和比较，并介绍了设计一个复杂的系统时通常采用的策略。     

基于OAI的数字图书馆中元数据互操作框架

提出一种基于最新的元数据互操作协议———OAI的元数据互操作框架。文章给出了框架中各个组件的模块及功能说明,并说明各模块之间的交互。这种框架克服了以前人们所提出的其他集成方法过于复杂、难于实施的缺点。     

Extending OAI-PMH over structured P2P networks for digital preservation

Open archives initiative (OAI) allows both libraries and museums create and share their own low-cost digital libraries (DL). OAI DL are based on OAI-PMH protocol which, although is consolidated as a pattern for disseminating metadata, does not rely on either digital preservation and availability of content, essential requirements in this type of system. Building new mechanisms that guarantee improvements, at no or low cost increases, becomes a great challenge. This article proposes a distributed archiving system based on a P2P network, that allows OAI-based libraries to replicate digital objects to ensure their reliability and availability. The proposed system keeps and extends the current OAI-PMH protocol characteristics and is designed as a set of OAI repositories, where each repository has an independent fail probability assigned to it. Items are inserted with a reliability that is satisfied by replicating them in subsets of repositories. Communication between the nodes (repositories) of the network is organized in a distributed hash table and multiple hash functions are used to select repositories that keep the replicas of each stored item. The OAI characteristics combined with a structured P2P digital preservation system allow the construction of a reliable and totally distributed digital library. The archiving system has been evaluated through experiments in a real environment and the OAI-PMH extension validated by the implementation of a proof-of-principle prototype.     

一种基于移动Agent的数字图书馆互操作框架

互操作是实现数字图书馆（DLs)的集成（或联邦）需要解决的关键问题，其目的是将Web上广泛分布的，自治的，异构的DLs联合起来，利用统一的查询界面实现对多个DLs的透明访问，首先介绍了DLs互操作的实现方法，并指出了各自的优缺点：在此基础上，提出一种基于移动Agent的DLs互操作框架，并给出了基于该框架实现的一个原型系统。     

网格环境下基于OAI的数字图书馆互操作机制

现有数字图书馆（DLs）互操作方案，在实现大规模数字图书馆集成方面都存在一定的局限性。该文将网格技术与OAI-PMH框架相结合，提出了一个数字图书馆网格（DL Grid）互操作框架，并对网格环境下元数据资源的发现、采集、重组等关键问题进行了分析和设计，初步实现了在集成的元数据基础上数字图书馆信息的共享。     

基于OAI的科学数据共享平台研究与设计

针对科学数据共享工程中元数据地理位置分散、标准不统一、元数据收割自动化程度不高等问题,结合OAI协议简单、低门槛、跨平台、互操作强等特点,把OAI协议应用到大同地区科学数据共享平台的建设中。各数据分中心作为数据提供者,基于XML技术向共享平台发布元数据。共享平台作为服务提供者,定期收割各数据分中心的元数据,加工处理后存储在当地数据库中,为用户提供一站式数据服务。实践证明,该方法操作简单,易于实现,为快速、高效地整合集成科学数据提供了一种有效的方法。     

Query generation for retrieving data from distributed semistructured documents using a metadata interface

We describe a method for generating queries for retrieving data from distributed heterogeneous semistructured documents, and its implementation in the metadata interface DDXMI (distributed document XML metadata interchange). The proposed system generates local queries appropriate to local schemas from a user query over the global schema. The system constructs mappings between global schema and local schemas (extracted from local documents if not given), path substitution, and node identification for resolving the heterogeneity among nodes with the same label that often exist in semistructured data. The system uses Quilt as its XML query language. An experiment is reported over three local semistructured documents: ‘thesis’, ‘reports’, and ‘journal’ documents with ‘article’ global schema. The prototype was developed under Windows system with Java and JavaCC.     

Improving interoperability using vocabulary linked data

The concept of Linked Data has been an emerging theme within the computing and digital heritage areas in recent years. The growth and scale of Linked Data has underlined the need for greater commonality in concept referencing, to avoid local redefinition and duplication of reference resources. Achieving domain-wide agreement on common vocabularies would be an unreasonable expectation; however, datasets often already have local vocabulary resources defined, and so the prospects for large-scale interoperability can be substantially improved by creating alignment links from these local vocabularies out to common external reference resources. The ARIADNE project is undertaking large-scale integration of archaeology dataset metadata records, to create a cross-searchable research repository resource. Key to enabling this cross search will be the ‘subject’ metadata originating from multiple data providers, containing terms from multiple multilingual controlled vocabularies. This paper discusses various aspects of vocabulary mapping. Experience from the previous SENESCHAL project in the publication of controlled vocabularies as Linked Open Data is discussed, emphasizing the importance of unique URI identifiers for vocabulary concepts. There is a need to align legacy indexing data to the uniquely defined concepts and examples are discussed of SENESCHAL data alignment work. A case study for the ARIADNE project presents work on mapping between vocabularies, based on the Getty Art and Architecture Thesaurus as a central hub and employing an interactive vocabulary mapping tool developed for the project, which generates SKOS mapping relationships in JSON and other formats. The potential use of such vocabulary mappings to assist cross search over archaeological datasets from different countries is illustrated in a pilot experiment. The results demonstrate the enhanced opportunities for interoperability and cross searching that the approach offers.     

数字图书馆网格互操作框架

随着全球数字图书馆(DLs)的迅猛发展,互操作成为亟待解决的重要问题。目前DLs互操作的主要解决方案包括:分布式搜索、元数据收集、中间件技术等,在实现大规模的数字图书馆互操作方面都存在一定的局限性。文章通过对已有方案的分析和对比,指出各自的优势和不足,并在OAI-PMH框架的基础上,结合先进的网格技术,提出全新的数字图书馆互操作框架—数字图书馆网格DLGrid,为解决大规模数字图书馆的互操作提供一种新途径。     

Variable linkage for multimedia metadata schema matching

Today there are many media sharing applications that use diverse metadata formats to describe media resources. This leads to interoperability issues in cataloguing, searching and annotation. This situation poses schema matching algorithms in the eye of the storm of metadata interoperability. In this paper we present two different solutions for multimedia metadata schema matching using variable linkage algorithms. These methods consist in directly comparing the data values stored in the different metadata variables, allowing to overcome the inherent limitations of schema-level matching approaches. We show the feasibility of these methods through some experiments with real metadata information extracted from the image hosting websites Deviantart, Flickr and Picasa.     

支持OAI-PMH的元数据互操作体系结构设计与实现

随着全球数字图书馆的迅猛发展,互操作成为亟待解决的重要问题。OAI-PMH协议的制定为在元数据级别上设计实现一个统一、高效的互操作框架创造了条件。文章基于北京大学数字图书馆项目,详尽阐述了一个典型的支持OAI-PMH互操作体系结构的完整的设计与实现;不仅包括在理论上逻辑清晰的设计方案,在实现上也采用了比较成熟又兼具理论和应用前景的技术,如Java、DOM、XML、Oracle9i等。该文的工作为将来联合式数字图书馆这一发展方向做出了很好的尝试。     

图书馆元数据信息发布平台及其应用

文中研究了图书馆信息服务。信息服务呈现多元化、个性化的趋势,根据需求定制服务十分重要,图书馆信息可以重复利用是服务定制的保障。提出元数据信息发布平台设计方案,发布平台利用中国机读目录抽取信息,并结合互熵一信息检索方法提高抽取信息的正确性,抽取的信息以元数据形式存储,通过OAI协议发布。给出发布平台的应用实例,说明信息发布平台如何为毕业设计过程管理系统提供数据服务。     

Dr. Hadoop: an infinite scalable metadata management for Hadoop—How the baby elephant becomes immortal

In this Exa byte scale era, data increases at an exponential rate. This is in turn generating a massive amount of metadata in the file system. Hadoop is the most widely used framework to deal with big data. Due to this growth of huge amount of metadata, however, the efficiency of Hadoop is questioned numerous times by many researchers. Therefore, it is essential to create an efficient and scalable metadata management for Hadoop. Hash-based mapping and subtree partitioning are suitable in distributed metadata management schemes. Subtree partitioning does not uniformly distribute workload among the metadata servers, and metadata needs to be migrated to keep the load roughly balanced. Hash-based mapping suffers from a constraint on the locality of metadata, though it uniformly distributes the load among NameNodes, which are the metadata servers of Hadoop. In this paper, we present a circular metadata management mechanism named dynamic circular metadata splitting (DCMS). DCMS preserves metadata locality using consistent hashing and locality-preserving hashing, keeps replicated metadata for excellent reliability, and dynamically distributes metadata among the NameNodes to keep load balancing. NameNode is a centralized heart of the Hadoop. Keeping the directory tree of all files, failure of which causes the single point of failure (SPOF). DCMS removes Hadoop’s SPOF and provides an efficient and scalable metadata management. The new framework is named ‘Dr. Hadoop’ after the name of the authors.     

Integrated access to legal literature through automated semantic classification

Access to legal information and, in particular, to legal literature is examined for the creation of a search and retrieval system for Italian legal literature. The design and implementation of services such as integrated access to a wide range of resources are described, with a particular focus on the importance of exploiting metadata assigned to disparate legal material. The integration of structured repositories and Web documents is the main purpose of the system: it is constructed on the basis of a federation system with service provider functions, aiming at creating a centralized index of legal resources. The index is based on a uniform metadata view created for structured data by means of the OAI approach and for Web documents by a machine learning approach, which, in this paper, has been assessed as regards document classification. Semantic searching is a major requirement for legal literature users and a solution based on the exploitation of Dublin Core metadata, as well as the use of legal ontologies and related terms prepared for accessing indexed articles have been implemented.

基于网格技术的数字图书馆互操作研究

互操作是实现数字图书馆集成或联邦的中心问题。对目前流行的几种数字图书馆互操作解决方案进行分析和对比,指出各自的优势和不足。在此基础上引入网格技术,提出一种基于网格技术的增强型互操作体系结构。对该体系结构进行具体分析。     

Improving dissolve spatial operations in a simple feature model

This paper presents an algorithm to improve the performance of a spatial operation called ‘dissolve’ widely used in Geographic Information System (GIS) through spatial database systems. In simple feature models (lacking of persistent topology) executing some common spatial operations requires a high amount of system resources. Such common operations occur for example in the ‘OpenGIS Simple Features for SQL’ protocol (SFS), a client-server interoperability standard defined by ‘The Open Geospatial Consortium, Inc.’ (OGC). The specific spatial operation studied in this paper is called ‘dissolve’. It is carried out using the union spatial operator defined by OGC) and consists of removing the boundaries between adjacent polygons. The proposed algorithm improves substantially the performance of this spatial operation and it needs between 100 and 1000 times less amount of resources. This way it enables the database server to carry out this spatial operation on huge datasets containing up to millions of geometries. To check and to validate this algorithm a new open source software package (PGAT) has been developed.     

数字图书馆元数据互操作机制的研究

元数据是数字图书馆建设的关键技术之一,随着越来越多的元数据标准的出现,元数据的互操作问题已成为数字图书馆互操作的一个重要方面。分析元数据互操作产生的原因,从技术角度总结和研究元数据互操作的主要解决途径, 指出存在的问题,最后给出利用网格技术实现元数据互操作的思路。     

元数据在数据库互操作中的应用

数据库互操作技术是信息资源共享的关键技术,也是目前数据库技术领域关注的热点之一.对基于元数据的数据互操作技术的研究内容和现状进行总结,从元数据生命周期的角度给出数据库互操作技术分类体系,从元数据提取技术和元数据模型转换技术两方面进行归纳,给出主要的算法模型,对比分析各算法的优缺点,指出数据库互操作技术未来的研究趋势和挑...     

DCFS2的元数据一致性策略

随着集群应用对机群文件系统的性能、容量和规模等需求的日益增长,采用多元数据服务器是机群文件系统发展的必然趋势．基于多元数据服务器的分布式元数据处理是文件系统研究的一个重要问题．机群文件系统DCFS2采用分布式日志技术和改进的两阶段提交协议解决了分布式元数据处理下元数据的一致性问题．性能测试结果表明,DCFS2所采用的基于分布式日志的元数据处理策略能够提供高的I／O性能,并能够保证在元数据服务器失效后文件系统快速恢复．