One of the great advantages of the OpenDocument format is that it is simply a zip file. You can unzip it with any archiver and take a look at the contents (which is a set of XML documents and associated data), change it, re-zip it and you have a new document. But, the OpenDocument Format specification, section has one little extra restriction when it comes to zip containers. The file called “mimetype” must be at the beginning of the zip file, it must be uncompressed and it must be stored without any additional file attributes. If you don't do this then many applications (such as Officeshots.org) may refuse to open your documents. In this article I will show you how to correctly create ODF documents using zip.