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GI-axe: an access broker framework for the geosciencesE. Boldrini, S. Nativi, M. Santoro, F. Papeschi, P. MazzettiESSI-lab of IIA, CNR, Prato, Italy [email protected]
1. Query
2. Results: Metadata
1. Order
2. Results: Data
+ + +
User formulates a query by grouping a set of constraints and sends it to one of the GI-cat interfaces.
The result is detailed information (e.g. compliant with ISO 19115, GeoAtom, ...) about the matching datasets, including identi�cation, citation and distribution information.
(e.g. tornado events) (e.g. in the US) (e.g. acquired Feb 2009) (e.g. published by Unidata)
The retrieved datasets comply with the requested CGE, so they are more easily processed by end user applications.
#1 Discovery
#2 Access GI-axe: Access Broker
Use cases1) Data providers which have their datasets already published (e.g. on a FTP service) and wan-ting to have them readily published through di�erent access services (e.g. WCS, WMS).
Above example: Unidata IDV connects to GI-axe WMS to show a coverage natively available on a THREDDS OPeNDAP.Another client (e.g. NASA Panoply) accesses instead a NetCDF coverage retrieved through the GI-axe WCS.
2) Service providers wanting to let users retrieve and combine multiple datasets already pu-blished by di�erent services (e.g. WFS, WCS, OPeNDAP); enabling thus higher level applications and processing (e.g. multidisciplinary overlays).
Above example: The GI-portal client orders the GEO DAB to retrieve and overlay heterogeneous datasets available from di�erent access services: OGC WMS, WFS and WCS, FTP server and THREDDS OPeNDAP.
CNR/IIA
GI-axe has been �rst developed and experimented in the multidisciplinary interoperability framework of the European Commnity funded EuroGEOSS project. Presently, is utilized in the GEOSS Discovery & Access Brokering framework (GEO DAB).
XML
<Dublin Core>
XML
<ISO 19139>
from many ... to many ...
from many ... to many ... (by many)
The GI-cat discovery broker enables search of geo-data through several heterogeneous data sources.GI-cat mediates between the the many clients and the many providers available in the geoscience community.
GI-cat: Discovery Broker
User orders the AB to download the just discovereddatasets on a Commong Grid Environment (CGE).
(input metadata) (resolution)(CRS) (subset) (format)
+ + + +XML
<ISO 19139>
XML
<Dublin Core>
Access servicesOGC WCS 1.0.0, 1.1.2 , 2.0.1OGC WMS 1.1.0, 1.3.0OGC WFS 1.0.0. 1.1.0THREDDS 1.0.1, 1.0.2OPeNDAPFTPWAFNetCDFHDF
...
GI-axe is a �exible, component-based access broker which is capable to retrieve geo-data according to the CGE speci�ed by the User (a combination of grid CRS, resolution, extent and format of a dataset).GI-axe intermediates the di�erent access and transformation standards and complements, rather than sup-plant, the capabilities of the brokered access services.
Many user applica-tions, portals, clients:supported standards
Discovery servicesOGC CSW
OAI-PMH 2.0OpenSearch
GI-cat extended Web interfaceFTP interface for GEONETcastRESTful transactional interface
CSW 2.0.2 AP ISO 1.0CSW 2.0.2 ebRIM EOCSW 2.0.2 ebRIM CIMESRI GEOPORTAL 10
OpenSearch 1.1OpenSearch GENESI DROpenSearch 1.1 ESIP
Access servicesGI-axeWCS 1.0.0, 2.0.1WMS 1.1.1, 1.3.0WPS 1.0.0WFS 1.0
...
...
...
Many user applica-tions, libraries, clients:supported standards
Many transformation services
...
...
...
Many geo-data sources and resources:supported standards
Discovery/Inventory/Listing/Data Handling servicesOGC WCS 1.0, 1.1, 1.1.2 , 2.0OGC WMS 1.3.0, 1.1.1OGC WFS 1.0.0OGC WPS 1.0.0OGC SOS 1.0
HMA CSW 2.0.2 ebRIM/CIMESRI ArcGIS Geoportal (version 10) catalog service
SOS
OGC CSW 2.0.2 CoreOGC CSW 2.0.2 AP ISO 1.0OGC CSW 2.0.2 ebRIM/CIMOGC CSW 2.0.2 ebRIM/EO
CDI 1.04, 1.3, 1.4 1.6
GI-cat 6.x, 7.x
GBIF
GeoNetwork (versions 2.2.0 and 2.4.1) catalog service
Deegree (version 2.2) catalog service
OpenSearch
Flickr accessor
1.1 accessor
OAI-PMH 2.0 (support to ISO19139 and dublin core formats)
INPE HTTP Web interface
Hydro
GeoRSS 2.0
THREDDS 1.0.1, 1.0.2
THREDDS-NCISO 1.0.1, 1.0.2
ISO19115-2GeoRSS 2.0GDACSDIFGeneric File systemSITAD (Sistema Informativo Territoriale Ambientale Diffuso)WAF 1.0FTP
NetCDF (CF, OD)NCML (CF, OD)HDF
Many geo-data access sources and resources:supported standards
ComponentsPro�lersEach pro�ler publish a speci�c access interface (e.g. WCS, WMS, ...) : it mediates betwe-
en user applications and the internal GI-axe components. A client application request is thus translated to a GI-axe data retrieval order on a particular Common Grid Environment.
DistributorThe incoming order is distributed to the available (and useful) data accessors.
Data AccessorsData Accessors are in charge of retrieving data from the remote access services.
Each accessor can connect to particular service type (e.g. WCS, OPeNDAP, ...).A GI-axe retrieval order is thus translated in appropriate remote service requests.All the transformations (e.g. interpolation, subset, ...) are demanded to the remote service (as long as it supports them).
SupplementerIn case the remote service isn’t capable of certain transformations requested by the user
(e.g. interpolation, subset, ...) the supplementer component �nds suitable transformation ac-cessors which can provide the missing capabilities.
Transformation AccessorsTransformation Accessors are in charge of using remote transformation services to
apply the required transformations. E.g.: a client may require CRS reprojection of a dataset pu-blished only on a FTP service. A Matlab web processing service can be used in this case.
<GML>
