Electronic resources often include components with characteristics found in multiple classes of materials
Cataloging description is therefore often based on multiple AACR chapters
Always use chapter 9
Also chapters 2-8 when applicable for primary content
Also chapter 12 when continuing (serial or integrating)
Example: an online integrating cartographic database: requires use of chapters 3, 9, and 12
MARC coding also needed for multiple aspects: primary content, electronic aspects, continuing aspects, etc.