66 XSLT is its flexibility. Indeed, the style sheet can easily be modified e.g. on client’s
request to addretrievemodify filtering rules at the DMS.
12.1.3 Densification
The purpose of the Densification module is for the client to be able to specify arithmetic computation options to be applied to the data at the DMS. To justify the need for such an
approach, we will consider here that the DMS can receive data intended for the client from different sources. In this case, it may possible that the property value of a feature
differ from one source to the other.
Given that the client has either subscribed for or requested the data in the first place, the DMS is to send them regardless of their “cardinality”. However, as one of the key interest
of the DMS presence is to reduce bandwidth, sending several time the same or close to same feature, with only some properties slightly changing from one to the other does not
appear efficient.
The basic concept of the Densification module would be to send once all the common properties of the given features while providing computation of the values that varies
from a source to the other.
It is considered here that we are only looking at numerical values. Geometrical or qualitative values are left out of the scope of this study. This considered, the operations
that the DMS shall apply on a set of property values describing one feature are the following or combinations of the following:
The DMS calculates the mean of all the values provided, thus sending to the client a single value that represent the trend of the property based on the different
sources. The DMS calculates the standard deviation of all the values provided. This
information, combined with the mean calculation, provides further information on the dispersion of the data provided by the different sources
The DMS provides the range of the values provided, informing the client on the maximum offset between values provided by different sources.
Use or use of combination of those computed values provides the client with extended information on the differences noted among the data sources while optimizing the amount
of data exchange on the data link.
12.1.4 Recommended approach
