= GenericTrac Data Model = 

This is an experimental branch for trying out the various ideas exposed in the recent proposals:
 - TracDev/Proposals/DataModel
 - TracDev/Proposals/Journaling
 - WikiContext are used as ''resource descriptors'' and have a `.resource` field 
   which enables one to fetch the corresponding data model instance

See also [googlegroups:trac-dev:8cf3f5fe0e476ce5 this mail].

== Design Notes ==

As this will be a major redesign of the data model, it will also be a good opportunity to tackle the ''[TracMultipleProjects multiple project support]'' in Trac (#130).

Each resource related table should probably get a `project` identifier field.

== Current Status ==

=== TODO ===
 - modify the Milestone module so that it uses the new proposed datamodel. See [#TheMilestoneExample].
 - experiment new tabbed view for the milestone (''View'', ''Discussion'', ''History''). See TracProject/UiGuidelines.
 - milestone should be able to have attachments, too (#3068)
 - adapt the Roadmap module to the new model
 - adapt the Milestone admin component to the new model

Once this is complete, validate the genericity by promoting the components to be first class resources as well (#1233).


Working on the generic aspect of Trac should also make it possible to implement various ''generic'' operations on Trac resources as plugins, mainly being able to (re-)implement TracCrossReferences as a plugin.


=== DONE ===
 - ''Not yet started''

== The Milestone Example ==

The proposed data model would be:
{{{
#!sql
-- record Milestone current properties
-- 
create table milestone_prop (
 project text,
 id    text,
 --
 name  text,
 value text
);

create index milestone_idx on milestone_prop (id, name);

-- record Milestone change metadata
--
create table milestone_revision (
 tid            int primary key,
 --
 date           int,
 authname       text,
 author         text,
 ip             text,
 authenticated  int
);

create index milestone_date_idx on milestone_revision ( date );
create index milestone_authname_idx on milestone_revision ( authname, authenticated );

-- Track changes of Milestone properties
--
create table milestone_change (
 tid   int,
 project text,
 id    text,
 --
 name  text,
 value text,
 unique (tid, project, id)
);

-- record Milestone metadata
--
create table milestone_schema (
 project  text,
 name     text,
 --
 revprop  char,
 type     text,
 detail   text,
 value    text,
 order    int,
 unique (project, name)
);
}}}

The existing `milestone` table can be kept, it will simply not be used anymore.
This will allow to test the branch within existing environments.

The `name` is not unique in `milestone_change`, to allow multiple values (#918)