C H A P T E R
20
Data Analysis and Mining
Practice Exercises
20.1 Describe benefits and drawbacks of a source-driven architecture for
gathering of data at a data warehouse, as compared to a destination-
driven architecture.
Answer: In a destination-driven architecture for gathering data, data
transfers from the data sources to the data-warehouse are based on
demand from the warehouse, whereas in a source-driven architecture,
the transfers are initiated by each source.
The benefits of a source-driven architecture are
•
Data can be propagated to the destination as soon as it becomes
available. For a destination-driven architecture to collect data as
soon as it is available, the warehouse would have to probe the
sources frequently, leading to a high overhead.
•
The source does not have to keep historical information. As soon
as data is updated, the source can send an update message to
the destination and forget the history of the updates. In contrast,
in a destination-driven architecture, each source has to maintain
a history of data which have not yet been collected by the data
warehouse. Thus storage requirements at the source are lower for
a source-driven architecture.
On the other hand, a destination-driven architecture has the following
advantages.
•
In a source-driven architecture, the source has to be active and
must handle error conditions such as not being able to contact the
warehouse for some time. It is easier to implement passive sources,
and a single active warehouse. In a destination-driven architecure,
each source is required to provide only a basic functionality of
executing queries.
•
The warehouse has more control on when to carry out data gath-
ering activities, and when to process user queries; it is not a good
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