Xerox Paris, a document system Support & Software 用户指南

A page definition (or page def) contains the page settings such as the page
orientation, input tray, printable area and the information which breaks up and
positions the printstream data on the page into text blocks. A page 

def, therefore,

defines the attributes of the page and how and where the text blocks are to appear
on the page.

If we look at the View/Change Page Definition dialogue for page 

def ‘Page1’ of the

MileSaver model environment, we can see the settings for the attributes and text
blocks.

Setting the page definition is described in Chapter 3, Designing your First
Environment, the following sections describe why and how to use page definitions in
an environment