Start with the {@link org.eclipse.birt.chart.model.impl} package to determine what type of chart needs to be created.

The model.* packages represent the core chart model interfaces and enumeration classes generated using EMF
The model.*.impl packages represent the core chart model implementation classes generated using EMF
All other packages are dependencies and indirect references from the core model.

Read about EMF (Eclipse Modelling Framework) at http://www.eclipse.org/emf
See the official BIRT Chart FAQ at http://www.eclipse.org/birt/faq/Charts_FAQ.doc
Post your questions at the BIRT Newsgroup at http://www.eclipse.org/newsportal/thread.php?group=eclipse.birt
Report a bug at https://bugs.eclipse.org/bugs/enter_bug.cgi?product=BIRT