SDI Convergence - Nederlandse Commissie voor Geodesie - KNAW

multiple data services or resources to be accessed as if they were a single data service.
In a way this corresponds to the VirtualAddressDataService in Compartimos,
however, in OGSA CreateFederation, AddSourceToFederation, AddAccessMechanism,
and UpdateFederationAttributes federate a wide variety of services ranging from
input data resources to transformations of data and filters. In Compartimos a dataset
(the resource) is automatically included in the federation when it is published in the
catalogue and resources are, by definition, limited to address datasets. Therefore, VirtualAddressDataService
only has the GetAddress and UploadAddressData operations,
which mirror the AddressDataAccessService operations with the same names.
The VirtualAddressDataService is the centre of intelligence in Compartimos. Due to its
diverse capabilities, each within its own field of specialisation, it makes sense to combine
different components for an implementation of the VirtualAddressDataService. Below
a few examples:
1. the
OGSA-DAI Distributed Query Processing (DQP) (http://www.ogsadai.org/about/
ogsa-dqp/) could be employed for distributed queries;
2. the address matching functionality provided by independent
tools, such as the Af-
riGIS Intiendo address tool (Rahed et al., 2008) could be used to remove duplicates
and resolve disambiguities; and
3. any processing that is available as
an OGC WPS, which is a standardised interface
that facilitates the publishing of geospatial processes, and the discovery of and binding
to those processes by clients.
Di et al. (2008) implemented their own mediator for geographic data, the Intelligent
Grid Service Mediator (iGSM), while Shu et al. (2006) propose using OGSA-DAI DQP.
Once the address data has been consolidated, similar to the AddressDataAccessService,
an implementation of OGC WFS or OGSA-DAI data resources are potential technology
choices for the external interface of the VirtualAddressDataService.
4.5 The AddressDataset
The Compartimos AddressDataset object refers to any address dataset that is published
on the address data grid. In OGSA data architecture terminology this is the data
source or data resource. In Compartimos the data provider determines how address
data is stored. The AddressDataAccessService provides access to this proprietary data
in the prescribed way (according to the interoperable data model). However, for optimal
conversion efficiency it will make sense to store the ‘raw’ data according to the Compartimos
interoperable data model, or as close to it as possible.
4.6 The AddressService
The AddressService refers to any address-related service, such as routing or mapping,
that is offered by a third party on top of the single virtual address dataset in the grid.
The list of operations of the AddressService is application dependent and defined by
the service provider. The AddressService interacts with the VirtualAddressDataService
when executing its address-related service. The functionality and interface of this service
is determined by its purpose, and therefore not prescribed in Compartimos. For
interoperability, it is important that this service uses the same standard and protocol as
the other services in Compartimos.
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