• ActionHowToDeleteObjects

Action How To Delete Objects

Assigned

ABR+TSH+BAM

Prev assigned

Tasks adressed

TaskA.5

Time estimated

1md

Time used

0.5md

Priority

1

Status

Finished

Iteration

14

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!

2. an object deletion documentation as part of the datamodel documentation. DONE, changed in FedoraState

3. 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.
2. Find the list of objects 'e' that reference an object from 'v'
3. Remove from the list 'e' all objects in approved, and all objects in 'v'
4. If 'e' is not empty, the delete fails, and the user is notified about the contents of 'e'
5. 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

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• 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.

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• 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.