Database Server Models for WMS and WFS Geographic Web Services - Geographical Information Systems: Trends and Technologies - page 150

User oriented schema transformation

An alternative of mdWFS service is to let the user guide transformations.
Bucher and Balley (2007) defi ne a methodology to get a transformation
schema to adapt data to a specifi c application. The idea is, fi rst, to transform
the initial data model to adapt it to new requirements, then to get the
geographic data instances. Modifi cations of the initial data model are
performed step by step (e.g., selection, modifi cation of the data structure)
to obtain the fi nal structure. These modifi cations defi ne an algorithm to be
applied to get instances from the database. This is equivalent to a workfl ow
application illustrated in Fig. 4 (Bucher and Balley 2007), with an imperative
programming language, step-by-step modifi cations are specifi ed and then

Data provider

User System

Provide raw datasets
and metadata

Display discovery
metadata

Select a dataset

Display the conceptual
data schema

View of the conceptual
data schema
[displayed]

Specify a
transformation on
the schema view

Update

[non

fi tted for
use]

Sequence of
schema view
transformations

Sequence of data
and metadata
transformations

Validate the
schema view

[fi tted for
use]

Convert schema view
transformations into
data and metadata
transformations

Apply transformations

Dataset and
metadata
[customized]

Deliver customized
dataset

Fig. 4. Activity diagram: customization of a dataset.