From the ODF standard:

4.3.2Pre-Defined Metadata Elements

4.3.2.1<meta:generator>
The <meta:generator> element contains a string that identifies the OpenDocument producer that was used to create or last modify the document. This string should match the definition for user-agents in the HTTP protocol as specified in section 14.43 of [RFC2616]. The generator string should allow OpenDocument consumers to distinguish between all released versions of a producer.
Note: Release versions of a producer could be distinguished based on build ids or patch level information.
If an OpenDocument producer that creates a document cannot provide an identifier string, the producer shall not export this element. If a producer stores a modified document created by another producer cannot provide a unique identifier, it shall not export the original identifier belonging to the producer that created the document.

Section 14.43:
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14.43 User-Agent

   The User-Agent request-header field contains information about the
   user agent originating the request. This is for statistical purposes,
   the tracing of protocol violations, and automated recognition of user
   agents for the sake of tailoring responses to avoid particular user
   agent limitations. User agents SHOULD include this field with
   requests. The field can contain multiple product tokens (section 3.8)
   and comments identifying the agent and any subproducts which form a
   significant part of the user agent. By convention, the product tokens
   are listed in order of their significance for identifying the
   application.

       User-Agent     = "User-Agent" ":" 1*( product | comment )

   Example:
       User-Agent: CERN-LineMode/2.15 libwww/2.17b3