2.1.2 Parts
A Package is composed of multiple parts as specified in [ISO/IEC29500-2:2012] section 9.1. Each part has an associated content type that specifies the format it is persisted in. Each part can also be the target or the source of a connection between two parts called a relationship (section 2.1.3), as specified in [ISO/IEC29500-2:2012] section 9.3.
The valid parts, content types, required relationships, and optional relationships between all parts in this package are specified in Part Enumeration.