1.1.3 Why OPC?

Energistics chose to base EPC on OPC for several key reasons, which include:

• OPC is an existing, widely supported standard.
• It addresses the use cases and requirements of Energistics, as explained above. Namely, it specifically supports the loose coupling of multiple document parts into a coherent whole. It has the ability to appear as folder and file structure as well as a single file archive.
• It supports a rich and extensible mechanism for describing relationships between the package and individual parts or files within the package and resources external to the package.
• Various programming languages already provide wide support (read-write libraries) for OPC. These languages include: the Microsoft.NET framework and Java. Energistics SIG members have tested various tool sets, and several vendors, whose applications rely on very large 3D models and digital media, have field-tested it. These libraries handle the parts and relationships of the package.

• It is based on the commonly used ZIP file structure. In the absence of explicit support for EPC, developers can at least open the package and see the list of files using commonly available zip tools. (To open with a ZIP tool: Right-click the file; from the menu, choose "Open with"; and select or navigate to your ZIP tool.)