Multi-page sheet and coordinates
The set of all the pages of a document is termed a multi-page sheet. A multi-page sheet is obtained by merging the pages of the document top down, without any joints or gaps. The left edges of all the pages are placed on the same axis, which goes through the point(0,0). The sequence of the pages in the sheet depends on their order in the batch.
Two coordinate systems are used: global (spanning the entire document) and local (bound to a particular page). The only difference between them is that the global system has parallel shifts, with each page having its own shift.
For example, suppose a document has three pages of the following sizes: 2500x3500, 2400x3400, and 2300x3300. The global coordinates of the pages are then [0, 0, 2500, 3500], [0, 3500, 2400, 6900], and [0, 6900, 2300, 10200] (in the order [left, top, right, bottom]).
For relations between elements, the global coordinate system is used, so that relations such as BELOW are interpreted correctly.
Multi-page hypotheses
Hypotheses for the following elements may be located on multiple pages:- Group
- Repeating Group
- Table
- Region
- Object Collection