Spatial Data Warehouses - Data Warehouse Systems: Design and Implementation - page 456

a

Document
requirements
specification

Identify source
systems

Apply derivation
process

Late inclusion of
spatial support

b

Add
spatial
support

Validate
conceptual
schema with
users

Define final
conceptual
schema and
mappings

Define initial
conceptual
schema

Fig. 11.17 Steps of the source-driven approach for spatial data warehouses. ( a )
Requirements specification phase. ( b ) Conceptual design phase

the identification of the source systems that may serve as data providers for
the spatial data warehouse. External sources are not considered at this stage.
In the second step, these sources are analyzed to discover multidimensional
schema elements. No semiautomatic or automatic procedure has been
proposed in the literature for deriving the schema of a spatial data warehouse
from the schemas of source systems. Thus, this derivation process should be
conducted manually and must rely on the designers' knowledge of the business
domain and of spatial data warehouse concepts. The multidimensional
schema obtained, as well as the corresponding metadata, are documented
in the third step of the requirements specification phase.
In the first step of the conceptual design phase, a conceptual schema with
spatial elements is developed. This schema is shown to the users to determine
their interest and to identify elements that are important for analysis. The
users' recommendations for changes will be reflected in the final schema
obtained in the last step, where mappings between the source and data
warehouse schemas are also developed.

Late Inclusion of Spatial Support

This case occurs when the source systems do not include spatial data or
they do contain spatial data but the derivation process is complex and the
designers prefer to focus first on nonspatial elements and to address spatial
support later on. Thus, the design process proceeds as for a traditional data
warehouse with the addition of a step for adding spatial support. Note that
this support is considered only for the previously chosen elements of the
multidimensional schema. This is shown in Fig. 11.17 a and the upper path of
Fig. 11.17 b.