VO Registry 注册与查询 李长华

Registry  A registry is first a repository of structured descriptions of resources, building on concept of a VO resource defined by the IVOA Recommendation, “ Resource Metadata for the Virtual Observatory ” (RM)

IVOA Registry(1)  The IVOA Registry will allow an astronomer to be able to locate, get details of, and make use of, any resource located anywhere in the IVO space, ie in any Virtual Observatory. The IVOA will define the protocols and standards whereby different registry services are able to interoperate and thereby realise this goal.

IVOA Registry(2)  A searchable registry is one that allows users and client applications to search for resource records using selection criteria against the metadata contained in the records.

IVOA Registry(3)  A publishing registry is one that simply exposes its resource descriptions to the VO environment in a way that allows those descriptions to be harvested.

IVOA Registry(4)  A full registry is one that attempts to contain records of all resources known to the VO.  A local registry, contains only a subset of known resources. 

注册需求 — 内容（ 1 ） 资源描述：（资源元数据---curation metadata) 服务描述： （服务元数据） how to invoke the service, including inputs and outputs other characteristics of the service; in particular, metadata about the kind of data returned by the service. compliance details when the service is meant to be an implementation of a standard service.

注册需求 — 查询  Resources and Services can be searched for based on characteristics  Query results returned in machine- interpretable form  It should be possible to uniquely retrieve a description of a resource or service either via a unique ID or via a small and predictable set of metadata.

注册需求 — 处理 (1)  Be easy for data/service provider to register a new service.  Be easy or automatic to update the metadata associated with a resource or service.  Be easy to unregister a resource and service  The registry should expect that registered services may become temporarily unavailable.

注册需求 — 处理 (2)  The registry should account for the possibility that a service will become permanently unavailable without it being explicitly unregistered.  The registry system shall support classes of services sharing common characteristics where these shared characteristics can be specified once and then referred to from the implementing services.

元数据  RegistryMetadata RegistryMetadata A registry must maintain a minimal, standard set of metadata which describes itself.  ResourceMetadata Each resource listed in a registry must maintain a minimal, standard set of metadata which describes itself. ResourceMetadata

RegistryInterface  defining a standard query and harvesting interface.This will allow the communication between registries to be a standard, and allow external implementations that need access to a registry a standard for querying the Registry.

RegistryInterfaceRegistryInterface— 需求  The meaning and behavior of three types of search and six harvesting operations.  The required input arguments for each operation.  The XML Schema used to encode response messages.  The meaning of the output for each operation.

RegistryInterfaceRegistryInterface— 查询 (1)  Search :Constraint-based Searchingfor resources by means of a query using the Astronomical Data Query Language (ADQL  KeywordSearch :Keyword-based searching for resources whose descriptions contain words in an input string  GetRegistries :Finding other Registries. 

RegistryInterfaceRegistryInterface— 查询 (2)  All three operations share a common output format for the resource records that match the search criteria. (VOResource XML description)  IVOA searchable registries must implement all three method searchable registries

RegistryInterfaceRegistryInterface— 查询 (3)  Search( String adql) 输入： ADQL 查询串, 支持 Xpath 及 Xquery, 但必需服从 VOResource XML Schema

RegistryInterfaceRegistryInterface— 查询 (4)  KeywordSearch(String words, Boolean orValue) 输入： String words: 被查询的一个或多个关键字 Boolean orValue: logical operand : OR, AND

RegistryInterfaceRegistryInterface— 查询 (5)  GetRegistries() This operation is intended to be used by other searchable registries to locate harvestable registries.searchable registries 不带参数

RegistryInterfaceRegistryInterface— Harvesting(1)  harvesting is the mechanism by which a registry can collect resource records from other registries. This mechanism is used by full searchable registries to aggregate resource records from many publishing registries.  harvester (usually a searchable registry)searchable registry  harvestee (usually the publishing registry)publishing registry

RegistryInterfaceRegistryInterface— Harvesting(2)  OAI-PMH The Open Archives Initiative Protocol for Metadata Harvesting provides an application-independent interoperability framework based on metadata harvesting

RegistryInterfaceRegistryInterface— Harvesting(3)  Support for multiple return formats. the OAI Dublin Core format (mandated by the base OAI-PMH standard) and the IVOA VOResource metadata format  Harvesting by date.  Harvesting by category.  Marking records as deleted.  Support for resumption tokens.

RegistryInterfaceRegistryInterface— Harvesting(4)  Identify  ListIdentifiers  ListRecords  GetRecords  ListMetadataFormats  ListSets

RegistryInterfaceRegistryInterface— Harvesting(5)  Identify Output: all information required by the OAI-PMH standard on this registry.

RegistryInterfaceRegistryInterface— Harvesting(5)  ListSets Sets, as defined in the OAI-PMH standard, “ is an optional construct for grouping items for the purpose of selective harvesting ”

RegistryInterfaceRegistryInterface— Harvesting(6)  ListIdentifiers (from,until, m etadataPrefix，set, resumptionToken) 输入：from,until,set 都是可选的 Identifier,a globally unique URI that identifies that resource record.

RegistryInterfaceRegistryInterface— Harvesting(7)  ListMetadataFormats 输入： identifier 可选 返回： 1.the unique identifier of the item for which available metadata formats 2. all metadata formats supported by this repository.

RegistryInterfaceRegistryInterface— Harvesting(8)  ListRecords (from,until,set,resumption,metaprefix) harvest records from a repository 输入： from,until,set 可选的 metaprefix 必需 返回： 满足条件的记录

RegistryInterfaceRegistryInterface— Harvesting(9)  GetRecord(identifier,metaprefix) retrieve an individual metadata record from a repository 输入： 返回值：

注册实现  NVO NCASNCAS cgi+DB (publishing registry) STScISTScI asp+DB (searchable registry) Caltech Caltech WS+eXist(…)  AstroGrid WS+eXist(…) AstroGrid

主要资源链接  [WSDLv1.1] Christensen, E., Curbera, F., Meredith, G., & Weerawarana, S. 2001, Web Services Description Language v1.1, W3C Note 15 March 2001, Services Description Language v1.1  [Hanisch 2004] Hanisch, R. (ed.) et al. 2004, Resource Metadata for the Virtual Observatory, IVOA Recommendation, Metadata for the Virtual Observatory  [ADQL] Ohishi, M. et al. 2004, Astronomical Dataset Query Language, IVOA Working Draft (internal), Dataset Query Language  [XPath] Clark, J. and DeRose, S. 2001, XML Path Language (XPath) Version 1.0, W3C Recommendation 16 November 1999, Path Language (XPath) Version  [Schema] Fallside, D, and Walmsley, P. 2004, XML Schema Part 0: Primer Second Edition, W3C Recommendation 28 October 2004, Schema Part 0: Primer Second Edition  [OAI]