## Action

= Action How To Delete Objects =



## The persons assigned to the action

 Assigned:: ABR+TSH+BAM



## The persons that previously worked on this action

 Prev assigned::



## The tasks from the WBS that are adressed by this action

 Tasks adressed:: [[TaskA.5]]



## The time estimated for this action, Use the format Xmd, to indicate the number of man-days estimated

 Time estimated:: 1md



## The time used for this action so far. Same format as Time estimated

 Time used:: 0.5md



## The priority of this action. 1-9

 Priority:: 1



## The status of this action, legal values are 'Not described', 'Not started', 'In progress' and 'Finished'

 Status:: Finished



## The iteration that this actions belongs to

 Iteration:: 14



## Notes about this action, that should be viewable on other pages

 Notes:: 

== Problem ==

Deleting objects while maintaining referential integrity is a complex task. The action should provide a general algorithm for how to implement deletions, so that the DOMS will not be left in an inconsistent state, no matter how they are performed.


Consider the Reeltape object. Such an object has relations to a collection, a license, and a number of sides and recordings. Deleting this object will leave the sides and recordings isolated. Deleting everything it references will destroy the collection and licenses. Only deleting the objects in the view will work, but then deletions are subject to a specific view, which might still leave unwanted objects dangling just because they are not part of the view. 

A system that address all these issues should be devised. 

== Work ==

The Progress section below describes the current version of object deletion. To complete this action, we need:

 1. an internal meeting to make the final decision on how to delete objects. DONE!
 1. an object deletion documentation as part of the datamodel documentation. DONE, changed in FedoraState
 1. communication of this object deletion workflow to Mjølner (+feedback +?) DONE, skrevet til Lennert

== Progress ==

We agreed to the following formulation:
'''When deleting an object, you must delete all the objects in this objects view, but only if no object in the view is referenced from outside the view, except from a list of approved objects. Then purge the relations referencing objects in the view from all objects in the approved list'''. The approved list is supplied by the user; it contains the objects which are known to reference the objects to be deleted and deleting these references will be fine. 

Given: Object d (to be deleted). Objectlist approved (the approved objects)

The formal algorithm to do this is:

 1. Find the view 'v' of object d.
 1. Find the list of objects 'e' that reference an object from 'v'
 1. Remove from the list 'e' all objects in approved, and all objects in 'v'
 1. If 'e' is not empty, the delete fails, and the user is notified about the contents of 'e'
 1. If 'e' is empty 
    1.1 for all objects in approved, delete any relation they have to an object in 'v'
    1.1 mark all objects in 'v' as deleted


This system could still potentially leave dangling objects, if they are not in the view. This is unwanted.
== Checklist For Working On An Action ==



The Life Cycle of an Action:
 * ''Assign people for action definition'': Done at start of iteration status meeting. Fill out '''Assigned'''
 * ''Define the action'': Describe information about what is to be done and how. Fill out '''Tasks Addressed''' and '''Time Estimated'''.
 * ''Review the definition'': Get another project group member to review the action definition, and update it.
 * ''Assign people for action implementation'': Done by project manager, usually the same persons who wrote the definition. Fill out '''Assigned''' and '''Prev assigned''' if new persons are assigned.
 * ''Implement the action'': See details below
 * ''Review the action'': Get another project group member to review what is implemented (code and documentation), and update it.
 * ''Finish the action'': Change the status to "Finished" and update the "time used" field on the action page.

Please make sure that you address the below issues, when working on an action:



 * Update the state of the action to "In Progress" when you start working on it.

 * Check if the tasks addressed by this action have their status set to "In Progress". If that is not the case, then change the state of them.

 * Keep track of how much time that has been spent working on the action. If it addresses more than one task, then make a note on the action page about how much of the elapsed time that has been spent on the individual tasks. '''Hint:''' Continually updating the "Time used" field will make it easier for you.

 * Update the "Progress History" and documentation pages of each task addressed by this action when appropriate. This depends on the situation, but in general, the task pages should hold all important related information about the work done, experiences gathered, identified requirements and so on.