Package Model

A package is a logical entity that holds a collection of parts. The purpose of the package is to aggregate all of the pieces of a document (or other type of content) into a single object.
example: : A package holding a document with a picture might contain two parts: an XML markup part representing the document and another part representing the picture.
The package is also capable of storing relationships between parts.
The package provides a convenient way to distribute documents with all of their component pieces, such as images, fonts, and data. Although this Open Packaging specification defines a single-file package format, the package model allows for the future definition of other physical package representations.
example: A package could be physically represented in a collection of loose files, in a database, or ephemerally in transit over a network connection.

This Open Packaging specification also defines a URI scheme, the pack URI, that allows URIs to be used as a uniform mechanism for addressing parts within a package.