1 mapping the dais concepts simon laws (ibm) sastry malladi (oracle) savas parastatidis (univ. of...

1

Mapping the DAIS Concepts

Simon Laws (IBM)

Sastry Malladi (ORACLE)

Savas Parastatidis (Univ. of Newcastle)

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Background

Educate DAIS WG about web services infrastructure WS-I, WS-Context, WSRF

Do we have to make a choice of approach? Implicit vs explicit data resource addressing Service vs resource OGSA have chosen WSRF and the implicit approach

Currently it seems that the answer is yes The service consumer must take different actions

depending on whether an implicit or explicit approach is chosen

However approaches can be mixed and matched

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Approach

How do we access data resources through various web services based infrastructure?

Scenarios Stateful interactions with data resources Sessions with data services Discovery of data resources Access to metadata about data resources and/or services Third-party delivery

Infrastructures Web Services-Interoperability (WS-I) only specifications WS-I plus WS-Context WS-I plus WS-RF

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Scenario 1

Stateful interactions with data resources

Using WS-I only

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Scenario 1 - Using WS-I

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<dais:query> SELECT * FROM A</dais:query>

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<dais:datasetId> urn:dais:dataset:123</dais:datasetId>

urn:dais:dataset:123

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internal-id

mapping from externally visible

name to internal id(if required)

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<dais:sort> urn:dais:dataset:123</dais:sort>

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<dais:sort> urn:dais:dataset:123</dais:sort>

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<dais:analyse> urn:dais:dataset:123</dais:analyse>

replication (out-of-band)

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Scenario 1


Using WS-Context

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Scenario 1 - Using WS-Context

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<ctx:context> context-state</ctx:context>


context-state associated with local resources

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<dais:sort />


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<dais:sort />

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<dais:analyse />



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<dais:sort />


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<dais:use> urn:dais:dataset:123</dais:use>


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Scenario 1


Using WS-RF

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Scenario 1 - Using WS-RF

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<wsa:EndpointReference> <wsa:To> http://service.com/dataset </wsa:To> <wsa:ReferenceProperties> <dais:datasetId> urn:dais:dataset:123 </dais:datasetId> </wsa:ReferenceProperties></wsa:ReferenceProperties>

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urn:dais:dataset:123 mapping from externally visible

name to internal id(if required)

internal-id

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Scenario 1 - Using WS-RF

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<dais:query />

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<dais:datasetId> urn:dais:dataset:123</dais:datasetId>

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Observations

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DAIS and Naming

DAIS is specifically about accessing data resources We need to be able to give names to those data

resources OGSA V1 describes a three level naming

scheme Human Readable Names Abstract Names Address

The differences between the approaches lies in the abstract name to address mapping

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WS-I Registry

Consumer

header

Service

registry lookup

Service Address (URL) http://services/daisdsservice

message

Data Resource urn:dais:ds1

body

Resource Abstract Name e.g urn:dais:ds1

insert abstract name into message body

urn:dais:ds1 http://services/daisdsservice

Service logic is able to locate resource based on message body

URL

-Focus on services-Registy lookup can result in many service URLs- A service can act on many resources-One or more resources can be specified in the message body at service call time - Abstract names can be passed to any service than understands them

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WS-I + WS-Context Registry

Consumer

header

Service

registry lookup


message


body


insert context into message header

urn:dais:ds1 http://services/daisdsservice

Service logic is able to locate resource based on context in message header

Context

associate resource name with context

URL

-Focus on services-Context supports a sequence of messages across many services-Registy lookup can result in many service URLs- A service can act on many resources-One or more resources can be associated with a context

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WS-RF Registry

Consumer

header

Service

registry lookup


message


body


insert reference properties into message header

urn:dais:ds1 EPR( http://services/daisdsservice, ds1)

Service logic is able to locate resource based on reference properties in header

EPR

-Focus on resources-Registy lookup can result in many EPRs- An EPR identifies one or more resources in the context of a service

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Do We Have To Make A Choice?

Mitigating the differences Optional discriminators in the message body WSDL binding operation parts WSRF TC in OASIS is considering embodiments of the

Implied Resource Pattern WS-Addressing EPR Singleton pattern Context based approaches

Living with the differences Mix and match

Ultimately the consumer of the service has to make a choice To put a resource discriminator in the message body or not

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General Issues

Stability of supporting infrastructure Interoperability and adoption Composability Tooling Conceptual model

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Questions

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1 mapping the dais concepts simon laws (ibm) sastry malladi (oracle) savas parastatidis (univ. of...

Documents

data resourcessessions

data resourceswe

data resources ogsa

service urls

backgroundeducate dais

ds1bodyinsert context

message bodyurlws

ds1 http