OGSA-DAI 简介及其它在 China-VO DAS 系统中的应用

杨阳

中国虚拟天文台研发团队

Chinese Virtual Observatory

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outline

• OGSA-DAI • DAI’s application -China-VO DAS• Extendable characteristics

-OGSA-DQP software

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OGSA-DAI

• KEY OGSA: Open Grid Service Architecture DAI: Data Access and Integrate WSRF: Web Service Resource

Framework DAS: Data Access Service

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What is OGSA-DAI ?

• OGSA-DAI is a middleware to assist with access and integration of data from separate sources via the grid.

It allows data resources, such as relational or XML databases, to be exposed on to Grids and to be accessed via web services.

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What can OGSA-DAI do ?

• Different types of data resources - including relational, XML and files - can be exposed via web services. A number of popular data resource products are supported.

• Data within each of these types of resource can be queried and updated.

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• Data can be transformed (using XSLT), compressed and decompressed (using ZIP and GZIP compression).

• Data can be delivered to clients, other OGSA-DAI web services, URLs, FTP servers, GridFTP servers, or files.

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• Requests to OGSA-DAI web services have a uniform format irrespective of the data resource exposed by the service. (though the actions specified within each request may be data resource-specific).

• Information on the data resources exposed by an OGSA-DAI web service and the functionality supported by the service can be accessed by clients.

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Architecture

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Important concepts

• Actions• Activity• Session• Perform document• Response document

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Actions

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Activity

• the operations that a data service resource can perform, including data resource manipulation, data transformation and data delivery operations

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Session

• objects for storing state in the data service resource across multiple requests.

session attributes life-time:creating accessing terminating explicit session implicit session

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Perform document• the documents used by clients to

describe the activities that they wish a data service resource to execute

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Response document• the documents that describe to clients

the results of the processing of perform documents by data service resources.

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DAI’s Application China-VO DAS

UserA UserB UserC

Catalog Query(VOQL) Plate Image

QueryAdvanced Image

QuerySpectrum Query

DAS(OGSADAI)(Parse ADQL Execute Plan )

Get metadata

User’ s Info/MySpace

User/sessionManagment

MySpaceManagment

Data Node(OGSADAI)

Data Node(OGSADAI)

Data Node(OGSADAI)

Registry

Registry

Registry

Result 1 Result 2

DataResourceDataResource

DataResource

DataResourceDataResource

DataResource

DataResourceDataResource

DataResource

DataResourceDataResource

DataResource

SynQuery/AsynQuery

URL/

GridFTP

12

数据流

3

0

Registry

Perform Perform Perform

transformFormat

URL/

GridFTP

transformFormat

PerformPerform Perform

crossMatch crossMatch

Perform

Get metadata

Get Status Get Status

MySpace

控制流

DeliveryToURL

Client

Registry

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Aspects from OGSA-DAI as support for VO DAS

• The basic operation to user registration database :delete 、 insert 、 update etc.

• ADQL query: synchronous and asynchronous• Get information: state and data URL• The basic operation to database in data node• Data can be transformed

VOTable 、 FITS 、 ASCII

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Extended characteristics

OGSA-DQP (Distributed Query Processing ) It is an example of a data integration

component • supports queries over OGSA-DAI data

services and over other services available on the Grid, thereby combining data access with analysis;

• adapts techniques from parallel databases to provide implicit parallelism for complex data-intensive requests; and

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DQP framework consists of : • Grid Distributed Query Service

(Coordinator) It is the main interaction point for the

clients • Query Evaluation Service (Evaluator) It is used by the coordinator to execute

query plans generated by the query compiler, optimiser and scheduler.

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More information is provided in the following address

OGSA-DAI: http://www.ogsadai.org.uk/

China VO: http://www.china-vo.org

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Thank you!