2.2.1 Content Type (Defined by OPC)
The root folder of an OPC package contains a special file with the reserved name [Content_Types].xml; this file must always be stored in the root. The purpose of this file is to define a specific mime content type for each part in the package. For more information on how this is used in EPC, see 3.3 Content Types (as used in EPC).
The mime-type mapping allows a level of indirection from file extensions (which can have different meanings in different systems) and an explicit type that software packages must support. It can also be useful:
- For XML content: if you have multiple versions of RESQML inside the same EPC container, you can use the mime type to determine which documents to validate.
- For non-XML content (such as PDF or application files, such as .docx), it provides a hint to the operating system about which viewers and editors support the content.