page 1© crown copyright 2006 registry technology & case study implementation j. tandy, d....

© Crown copyright 2006

Registry technology &

case study implementation

J. Tandy, D. Thomas - November 2006


What is a registry? - definition

A registry is an information

system on which a register

is maintained A register is a controlled

list of information

(ISO19135 Geographic Information –

procedures for item registration)Registry


Information hub

When combined with a

portal, the registry acts as

a hub within the distributed

data infrastructure …

Registry

Portal

Information resources

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In an information infrastructure such as WIS, a registry provides a focal-point for the propagation of best practice, standards and governance in addition to the discovery of information resources and services. The e-business XML Registry-Repository is the choice de jure for implementing a fully-functional, standards-based registry. The extensibility of e-business Registry Information Model enables the information infrastructure to grow and evolve as new requirements, content and service types emerge without needing to re-engineer the infrastructure.


<extent><EX_Extent> <geographicElement><EX_GeographicDescription><geographicIdentifier><MD_Identifier><code><gco:CharacterString>EGLL</gco:CharacterString></code></MD_Identifier></geographicIdentifier></EX_GeographicDescription></geographicElement></EX_Extent></extent>






Providing an aggregated

view of content from

numerous, heterogeneous

information resources


Propagation of standards

For content to aggregated into a single view, information resources (or services that expose them) must adhere to standards – WMO Core Metadata Profile ISO 191xx etc.

Publication of standards factored into simple modules promotes sharing, re-use & (eventually) interoperability

Registry

Portal

Informationmodels



Data standards


In an information infrastructure such as WIS, a registry provides a focal-point for the propagation of best practice, standards and governance in addition to the discovery of information resources and services. The e-business XML Registry-Repository is the choice de jure for implementing a fully-functional, standards-based registry. The extensibility of e-business Registry Information Model enables the information infrastructure to grow and evolve as new requirements, content and service types emerge without needing to re-engineer the infrastructure. Best

practice

Standards coordinator


Focal-point

Registry provides focal-point:

Registry

Portal





Propagating best practice, standards and governance

Discovering and exploiting information resources and services

Discovery metadata for content offerings

Service metadata for binding to information resources







Discoverymetadata

Search & browseby exposing

discovery metadata

Serviceinvocation

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Servicemetadata

Data


ebXML Registry-Repository

ebXML Registry-Repository provides generic content and metadata management services

Multiple components:Query manager & lifecycle managerAuthentication & authorizationMetadata registryContent repository

RepositoryItems: XML, documents, images, etc. …

RegistryObjects: describe RepositoryItems (metadata)

ebXML RR

Metadataregistry

Contentrepository


ebXML Registry Information Model (ebRIM)

ebRIM (ISO 15000-3) is the information model for the metadata registryCore information modelAssociation information modelClassification information modelProvenance information modelService information modelEvent information modelCooperating Registries info. modelAccess Control information model

Extensibility is most significant benefit

IdentifiableIdentifiable

RegistryObjectRegistryObject SlotSlot

ExtrinsicObjectExtrinsicObject

RegistryPackageRegistryPackage

AssociationAssociation

ClassificationClassification

ServiceService

AdhocQueryAdhocQuery

SubscriptionSubscription

……(Incomplete)


OGC Catalogue Services for Web (CSW)

ebXML-RR exposes query & lifecycle

management functionality via Registry

Services (ebXML-RS) As specified, ebXML does not support

geospatial or temporal queries Open Geospatial Consortium have

published a set of profiles for ebRIM

based on their Catalogue standard*:protocol bindingrecommended set of RegistryObject

fields based on Dublin Corespatio-temporal discovery capability

(* ISO 19115 profile also published)

ebXML RR

Metadataregistry

Contentrepository

OGC CSW interfaceOGC CSW interface


Oceans Portal – case study

The Oceans Portal provides key infrastructure components to support online discovery and access to marine information within Australian jurisdictions

It comprises of the following main components: A portal application (multiple entry-points to catalogue) A catalogue (registry – OGC CSW profile of ebRIM) Interoperable data and services (content offerings)

Online resources exposed by web-based portal, ranging from simple documents and web links through to complex, queryable datastores


Registering content in the Oceans Portal

ebXML RR

Metadataregistry

Contentrepository


Data provider

Registry client







Publish static ‘metadata’ records via registry client:• harvest control file• service bindings• custodian• classification(s) *• finder *• binder *

Where possible, the data provider is encouraged to re-use existing metadata

* optional

RegistryObjectRegistryObject




Volatile metadata harvested directly from service as specified by ‘harvest control file’ – ensures content offering is valid!

Data access service





The discovery model

The portal provides a general purpose discovery

model that will work for all types of resources, from

large structured databases supporting many different

queries to single documents. Discovery is based on the following principles:

Iterative, incremental filtering of results based on refinement of search parameters

Concurrent browse and search User-friendly exposure of underlying information model,

clear presentation of schemes used to classify content Ability to create re-usable ‘search links’; e.g. for publication

on homepage


Search ‘axes’ – GCMD topic & Species tax.


Search ‘axes’ – spatial extent


Search ‘axes’ – searchable metadata

ebXML RR

Metadataregistry

Contentrepository


Classification

Controlledvocabularies

Searchablemetadataelements

The ‘finder’ is aquery model for

accessing contentin the registry


Example – Sea Surface Temperature (1)

Search for ‘temperature’ within the topic browser …

Select ‘Sea Surface Temperature’ from results set …



Select a known area; ‘Great Barrier Reef’ … could enter coordinates …

But, I want to refine my search further …



Select ‘most recent SST analysis’ from drop-down list …

Only one result set … ask for ‘more info’ then ‘add to map’


The data access model

Having discovered content of interest, a user is able to ‘bind’ to the content …

A ‘binder’ is a Data Access Query Model (DAQM) used to define and present binding options:

service location protocol message structure permissible / appropriate values

Where possible, terms from the discovery phase (finder) are propagated through to the binder, ensuring simple, intuitive transition from discovery to access

Default binders include:WMS basic, WMS time, WFS, Document, Weblink and Event



Data access request processed ‘transparently’ … search parameters used to complete the service invocation – WMS-basic in this case


Conclusions

The Oceans Portal provides an excellent example of how an ebRIM registry can be used to underpin a spatial data infrastructure.

The capabilities provided overlap significantly with those required for WIS.

Oceans Portal is an extensible, flexible infrastructure that can grow and evolve as new requirements, content and services emerge.

The Oceans Portal is a strong candidate for use as the basis of a GISC-registry, providing proven capability whilst decoupling the registry & discovery portals from the underlying data services themselves.


Questions & Answers


THREDDS

THematic Realtime Environmental Distributed Data Services Offers significant utility for exposing ‘earth-science’ datasets Questionable extensibility:

THREDDS ‘discovery’ metadata record (similar to ebRIM RegistryObject) lacks extension points to add custom fields

Lack of ability to browse (& realise) non-hierarchical relationships between entities; although noted that hierarchies are user / community defined & a dataset may appear in (be classified by) more than one hierarchy

Limited bindings to data access services

The end of THREDDS? No … THREDDS catalogues could be

used to expose information resources that are aggregated

within a principal ebRIM registry THREDDS and ebRIM are seen to be complimentary

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