While we have
demonstrated that a filter can be applied to the data coming back from a Data Source,
we haven't discussed how a report user can specify what details they want to see.
In this chapter, we will look at the different types of parameters that BIRT offers. We
will distinguish between parameters that can filter Data Sets, and parameters that
can change the look and feel of reports. When it is completed, you will be able to take
your reports one step further than the canned reports that we have developed so far.
You will also be able to offer your users the ability to filter down large amounts of
data to justify the information that is important to them.
Why Parameterize Reports?
This is a very important question to ask ourselves, and while the answer might
seem obvious, it goes a little deeper: Imagine that you are a report developer for
a large organization with several different departments. Now you create a report
for a department that shows their costs for the fiscal quarter. That's great, and now
a second department asks you to create the same report for them. Then a third
department asks for a similar report; only they want to be able to see data for both
last quarter and this quarter. By this time, you have created three similar reports,
each representing the same set of data and running the same queries, only you have
hard-coded the department information.
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