Persistence of Data
Private vs. Public Information, page 12
While the contents of any particular stream in a compound document is defined entirely by the application or object that it contains, the management of streams and storages within the document is the responsibility of OLE itself. This means that it is possible for any application to browse through the structure and contents of the document - just as any application can open and read a disk file.
One of the nice results of this characteristic of compound document files is that you can mix private and public data within a file. You can, for example, place a plain text description in a stream with a given name that any application can read.
Microsoft has actually defined a standard properties format stream called the "SummaryInformation" field. This stream contains standard summary information such as the document Title, Author, Comments and so forth. This means that any application can read this summary information. You can use it in your own documents, or use it to obtain information about other documents that use this feature.
