Dear all,

before continuing this discussion, and before reinventing, you might want
to take a look at how org-id.el currently does create unique IDs.  In
particular, take a look at these variables:

org-id-prefix
org-id-method
org-id-include-domain

In particular, the docstring of the variable org-id-method is

  "The method that should be used to create new IDs.

An ID will consist of the optional prefix specified in `org-id-prefix',
and a unique part created by the method this variable specifies.

Allowed values are:

org        Org's own internal method, using an encoding of the current time
to
           microsecond accuracy, and optionally the current domain of the
           computer.  See the variable `org-id-include-domain'.

uuid       Create random (version 4) UUIDs.  If the program defined in
           `org-id-uuid-program' is available it is used to create the ID.
           Otherwise an internal functions is used."



Hope this helps.

Carsten


On Thu, Dec 22, 2016 at 10:02 PM, Eric Abrahamsen <eric@ericabrahamsen.net>
wrote:

> Christophe Schockaert <R3vLibre@citadels.eu> writes:
>
> > Eric Abrahamsen writes:
> >
> >> Karl Voit <devnull@Karl-Voit.at> writes:
> >>
> >>> I'd prefer using manually written :ID: instead since migration would
> >>> not be trivial to me.
> >>
> >> You could also use the `org-property-set-functions-alist' trick with
> the
> >> :ID: property. If you added an "ID" entry to that alist, Org's usual
> >> automatic id creation would be unaffected, but if you set ID manually,
> >> you could write a function that would first prompt for your
> >> human-readable string, then check for ID uniqueness and append random
> >> characters to your string until it was unique. I think that would be a
> >> nice addition to org-id.el.
> >>
> >> Eric
> > I thikn the tricky part would be that we can only ensure ID uniqueness
> > for the current agenda at the time of the ID creation. What if we later
> > merge another set of files where ID were created independantly to our
> > acustomed agenda files ?
> >
> > I like the idea of assigning a date since we would reduce chances to
> > define at the same time the same string and the same day. If meticulous,
> > we could assign a date and a time or random string as you suggest, Eric
> > (a tiny UUID :).
> >
> > I think I read somewhere the first inactive timestamp could be used to
> > tag an entry with a date. At least, I do that frequently.
> >
> > Thus, if available, we could even use it as a date when creating the ID
> > in order to have an indication of the creation time for the heading
> > instead of creation time of the link.
> >
> > Here it is for my suggestions.
> >
> > Dates might not be appropriate for every situation, though...
>
> I think including some sort of timestamp in the id would likely solve
> the problem of future conflicts. I don't think adding the actual date
> into the ID string would be that useful (how often would you be
> comparing dates from the ID property?), but the human-readable string
> could have a hash of the string plus (current-time) appended to it. Or,
> perhaps better, a hash of the outline path plus current-time.
>
> E
>
>
>