Part III covers the various ways that you work with data in your drawings. This part brings you to a new level of sophistication in terms of automation and interfacing with other drawings and data. Chapter 18 covers blocks and attributes, which enable you to work repetitively with objects and text. You can build intelligent, flexible blocks using the Dynamic Blocks feature. You can use attribute text to accurately place text and to create a simple database of information related to your objects. Chapter 19 explains how to refer to other drawings with external references, also called xrefs. Chapter 20 describes how to connect sophisticated external databases to objects in your drawings.