Complex sentence: The development of a computer-based information system includes a systems analysis phase which produces or enhances the data model which itself is a precursor to creating or enhancing a database (see Christopher J. Date "An Introduction to Database Systems").
Split into simpler sentences: The development of a computer-based information system includes a systems analysis phase. This helps produce the data model, a precursor to creating or enhancing a database (see Christopher J. Date "An Introduction to Database Systems").