3.5.2 Location of Core Properties in an EPC File

The location of the Core Properties part is specified in the OPC standards in chapter 11 as being the target of a well-defined package relationship. This means that the /_rels/.rels file in an EPC package must contain at least the following relationship:

<Relationship 
Id="<unique id>" Type="http://schemas.openxmlformats.org/package/2006/relationships/metadata/core-properties" 
Target="<location>"/>

Where:

• <unique id> is the identifier of the relationship (only needs to be unique within the relationship file).

• <location> is the location of the core properties part within the EPC file. A suggested location is in the “docProps” folder.
• As specified in the OPC specifications, the content type of a Core Properties part is: application/vnd.openxmlformats-package.core-properties+xml