Personal daily logs have already been in use for few years now in a small part of the organization. We have many truely working implementations.
Personal logging is a need expressed in documentation. It can be
seen as unstructured
documentation
activity, or rather, as a documentation activity whose only structure
is serialized time:
A log entry should answer the question what did I do so far, which
is not fully documented elsewhere?
A personal log can then contain any piece of information not yet structured, not yet part of the documentation system. Of course, that implies that this piece of information may never be actually merged or added to the existing documentation system: it does not matter, since a personal log is a document.
Personal logs are documents. As such, they need to be shared and persistent, as any other document. Of course, this sets limitations to their content, but that is solved with information sharing in general.
On the contrary of shared documents, since they reflect the work progress of a person, personal logs are owned by a person. This restriction is actually not significant in the current documentation system.
Personal logs are primarily read by the team organization.
Personal logs' content can then be actually refined according to the need of these readers.
The nature of the tasks tells how fine the log granularity should be: daily, weekly. As a rule of thumb, we recommend daily logs for all SW development tasks.
Of course, like in the case of documentation, personal logs should avoid duplication and overlapping. The problem quickly appears when the person has to report to different teams and projects using different formats, or different styles. Hyperlinks should be used to prevent this.