Java Reference
In-Depth Information
Chapter 2:
Designing a Database
In This Chapter
Like most of the chapters in this topic, this one is built around an example. In this
case, the example is a time and materials tracking and billing system. The objective is
to build a system capable of handling time and materials tracking and invoicing in
accordance with the Legal Electronic Data Exchange Standard (LEDES). Being a
published business, this is a good benchmark for a practical commercial application.
A primary consideration that went into defining the document structure was its
compatibility with existing legacy systems. LEDES mimics the existing paper process,
reflecting current time a nd materials invoicing practices in the legal profession.
Although the LEDES terminology derives from the legal profession, the
system is recognizable as a special case of a time and materials billing
system capable of handling multiple projects or matters within a single
invoice.
Note
Database Design Considerations
The most important consideration in designing a database is the application and its
requirements. For instance, the examples discussed in
Chapter 1
refer to a
Customers Table, containing the names, addresses, and phone numbers of individual
customers. This is a good approach when all the customers have unique addresses.
However, when an application needs to store information about individuals at a
corporation, many of those individuals work at the same location, so they have the
same address. In this case, it makes sense to have separate tables for contacts and
locations.
Like most organizations using time and materials billing, the legal profession focuses
a lot of effort on tracking the hours expended on a given project. Although lawyers
use slightly different terminology, and charge much higher rates, the process is much
like billing for contract programming. Usually, lawyers bill on a project basis, though
they call a project a
matter
. The legal term for tracking hours expended on a project is
capturing time
. Members of a law firm whose time is billable are referred to as
timekeepers
. Their time is billable at various predefined levels, ranging from partner
to clerk.
On of the most important aspects of any kind of system engineering is identifying the
needs of the users. In this application, the primary users are as follows:
Lawyers capturing time
Book keepers generating invoices
