I have no experience with topology validation in ArcGIS. I have polygon feature class.

When I create topology for this feature class, I specify two topology rules :

  • Must Not Overlap
  • Must Not have Gaps

After correcting all understandable artefacts, one problem remained visible on the map. I would like to ask you if I should to Mark as Exception?

enter image description here

  • 2
    Without access to the data, it would be very difficult to determine this. In the Error Inspector, what kind of error does it say this is? And is this picture the full extent of your data?
    – jcarlson
    Oct 1, 2020 at 12:21
  • Yes the image represents whole my study area. The Error Inspector tool says a "Must Not Have Gaps" rule error. Is there any possibility to share the shapefile in the forum? Oct 1, 2020 at 16:07
  • This is all the more strange because the study area was previously clipped out from a larger area ... Oct 1, 2020 at 16:29
  • Is the study area itself a polygon in this file? Must Not Have Gaps flags lots of exceptions such as boundaries.
    – danak
    Oct 21, 2020 at 18:16

2 Answers 2


I can see you still have an error at the lower left side of your image, maybe this is the reason why the whole study area is highlighted as red:

enter image description here

  • Yes..., I saw this error directly after I publicated my post. I corrected this artefact. Unfortunately topology still have one error in whole study area.... Oct 1, 2020 at 15:59

The outer box will always show as a gap. Once all other errors have been fixed, reassess the topology and verify this is the only remaining error in the error inspector. If the outer box is the only area, then dismiss it and continue with your process.

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