I think the most common way to audit/validate data is through filtered views, perhaps with some conditional formatting attached.
Here are some examples that might be displayed in Anaplan Dashboards:
Filtered view showing items where start date or end date are missing
Conditional formatting across the entire dataset highlighting where start date or end date are missing
From an Alert perspective, you could add a line item next to Start Date & End Date that evaluates to a (number) 1 if either is missing. Then, that 1 can be aggregated up to the parent level... if the parent value is > 0, you can present an Alert Message on, say, a landing dashboard, that asks the user to address the shortcomings... then provide a path to go review and fix the items. This same 1 can be aggregated further up the hierarchy so that higher level reviewers can understand who has issues to take care of.
I'm pretty sure, that when workflows are put in production, we'll be able to kick off data clean-up workflows... or otherwise include data cleanup activities as a step in the basic process.
Let me know if this helps. I'm interested to know how other folks manage data auditing.