SDI Convergence - Nederlandse Commissie voor Geodesie - KNAW

3. THE COMPARTIMOS REFERENCE MODEL
In this section we present the Compartimos (Spanish for ‘we share’) reference model,
which gives an abstract representation of the essential components and their relationships
that are required to share address data on a data grid in an SDI environment.
Compartimos was developed in order to analyse the requirements for realising a scenario
such as the one described above. For our research project, the Compartimos reference
model is described in terms of the five viewpoints of the ISO Reference Model
for Open Distributed Processing (RM-ODP) (ISO/IEC 10746:1998), i.e. the enterprise,
information, computational, engineering and technology viewpoints. In this article we
focus on the computational viewpoint, which is concerned with the functional decomposition
of the system into a set of objects that interact at interfaces - enabling system
distribution. Compartimos is based on the OGSA data architecture, which implies that it
follows a service-oriented approach and provides services similar to the OGSA data
architecture. Compartimos is a domain-specific application of the architecture, emphasising
address data in an SDI.
Table 1: Compartimos objects.
Object name Type Main purpose
Catalogue Data Stores information about services and data
CatalogueService Service Provides read and write access to the catalogue
VirtualAddressDataService Service Consolidates data
AddressDataAccessService Service Provides uniform access to individual address datasets
AddressDataset Data The individual address data set
AddressService Service A third party address-related service such as routing
or mapping
ReplicaService Service Replicates data in the address data grid
TransferService Service Transfers large volumes of address data
Table 1 lists the Compartimos objects and their purpose, while Figure 2 shows how the
Compartimos objects interact with each other in the address data grid. The word ‘object’
is used here in compliance with RM-ODP where it is used in the broader sense of
the word and not with its very specific interpretation in the object-oriented paradigm.
Some aspects of the OGSA data architecture, such as policies, storage management
and caching, are excluded from Compartimos because they can be used generically
for any kind of data and do not have to be tailored specifically for address data in an
SDI. In section 4 the purpose and capabilities of each Compartimos object are described
and related to the OGSA data architecture, along with the discussion of technology
choices. Compartimos’ ReplicaService and TransferService are sufficiently generic
to be excluded here.
4. TECHNOLOGY CHOICES FOR COMPARTIMOS OBJECTS
Table 2 provides an overview of available technology choices for Compartimos objects.
For each Compartimos object, there is also the option of developing it from scratch
without using existing technology, which has the same pros and cons of software reuse
that have been well documented over the years. Thus this choice is not discussed
here.
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