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https://issues.apache.org/jira/browse/CALCITE-4186?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17203729#comment-17203729
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Julian Hyde commented on CALCITE-4186:
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In [an email on
[email protected]|https://lists.apache.org/thread.html/r931fbaf041d6ccbb3a9ffe405e34d5d50ef8e5d85e68bafcfa0e1bf0%40%3Cgeospatial.apache.org%3E]
George Percival remarks (lightly edited for formatting and spelling):
{quote}The links that you provide for CALCITE draw on [this
blog|http://lin-ear-th-inking.blogspot.com/2007/06/subtleties-of-ogc-covers-spatial.html].
The blog proposes a {{Covers}} operation. I was not familiar with Martin’s
blog so had to reach out to some people more versed than me in Simple Features
and the DE-9IM. Surprisingly since the blog was written in 2007 and that it
also appears that {{Covers}} in in PostGIS, there is was no familiarity with
Martin’s blog.
If implemented in accordance with DE-9IM, there is no need to add a {{Covers}}
operation. Davis is pretty explicit in his blog about this assumption:
"Polygons do not contain their boundary". But DE-9IM, Simple Features and
published papers that led to the standards treat polygons as closed, i.e., the
polygons contain their boundaries.
Davis’s assumption that polygons are open, i.e., don't contain their boundary,
leads to a misinterpretation of the {{Contains}} operation. When implemented in
accordance with the standards, the addition of {{Covers}} is not needed.
Implementing Simple Features {{Contains}} consistent with the standard is a
better course than adding a {{Covers}} operation. The SF spec is free: [SF
spec|https://portal.opengeospatial.org/files/?artifact_id=25354].
{quote}
I find George's argument convincing, and conclude that it is not important to
implement {{ST_Covers}} and {{ST_CoveredBy}} in Calcite. {{ST_Relate}} would
still be very useful.
> Add ST_Covers, ST_CoveredBy, ST_Relate spatial functions
> --------------------------------------------------------
>
> Key: CALCITE-4186
> URL: https://issues.apache.org/jira/browse/CALCITE-4186
> Project: Calcite
> Issue Type: Bug
> Components: spatial
> Reporter: Julian Hyde
> Priority: Major
>
> Add {{ST_Covers}}, {{ST_CoveredBy}}, {{ST_Relate}} spatial functions.
> There are [subtle differences between ST_Contains and
> ST_Covers|http://lin-ear-th-inking.blogspot.com/2007/06/subtleties-of-ogc-covers-spatial.html];
> {{ST_Covers}} is usually what you want, and is easier to compute.
> Extend the Hilbert spatial index (added in CALCITE-1861) to handle
> {{ST_Covers}}, {{ST_CoveredBy}}, {{ST_ContainsPropertly}} as it does
> {{ST_DWithin}} and {{ST_Contains}}.
> It might make sense to also implement {{ST_ExteriorRing}} so that we can
> implement the [PostGIS example|https://postgis.net/docs/ST_Covers.html].
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