subtask vs issue "blocked by"

[Jira newbie]

Hello,

I find that near is the same to create a subtask vs create a linked task that is blocking a parent task. Would it be possible someone explain me which is the major difference and what seems better?

Thanks a lot and best regards,

[Donovan Baarda]

There is a subtle but important difference between prerequisite (blocking-task) and subcomponent (sub-task) relationships between tasks.

A sub-task is a small piece of work that is part of a larger parent-task. Completing the sub-task will partially contribute to completing the parent-task. The sub-task can and must be started and completed before the parent-task can be completed. A sub-task should have only one parent task, and a parent task can have multiple child-tasks.

A blocking-task is a set of work that is a pre-requisite for the blocked-task. The blocking-task is not part of the blocked-task, but the blocking-task must be completed before the blocked-task can even be started. A task can be blocking to multiple other tasks, and a task can be blocked by multiple other tasks.

The difference between these relationships is very important for planning tools like gantt-charts, with sub-component relationships used to estimate the total work required for large tasks, and pre-requisite relationships being important for ordering/scheduling of tasks. 

[Jack Brickey]

I see this to some degree as a personal preference thing. As Alexey mentioned sub-tasks do have some direct linkage w/ the parent. Typically a sub-task is a way of breaking down a task into smaller pieces to organize your work and track progress. Links are generally for showing indirect relationships between work items while sub-tasks, i would argue, are for direct relationships. Here is an example to drive my point.

Task 1: build a box

• sub-task - design box
• sub-task - obtain materials
• sub-task - construct box

Task 2: paint a box

• sub-task - choose paint
• sub-task - paint box
• >>>link to Task 1 "is blocked by"

Task 3: sell a box

• >>>link to Task 2 "is blocked by"

with all that said, one could certainly make task 2 and 3 sub-tasks of task 1 but then you lose any order relationship that a link could provide.

[Subramaniam Dasari]

If my 1st task is blocked for some reason, then can i put the 2nd task which is related to 1st one as dependent?

[Jack Brickey]

@Subramaniam Dasari a, not quite sure what you mean.

Link types are independent of one another but are paired with its mate. Examples

correct:

If A is blocked by B Then B blocks A

if A relates to B Then B relates to  A

A is blocked by B, B blocks A, and C relates to A and A relates to C

invalid:

If A is blocked by B Then B relates to A

[Alexey Matveev]

Hello,

Subtask is an internal link in Jira. There are additional features for this link. For example, in a board if you move all subtasks to the most right column, you will be asked to close the task. In the detail issue view all estimates and work logs can be summed from subtasks to tasks. Also if you open a subtask you can always see the parent task near the key of the subtask.