Talk:Well-known text

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Broken Link[edit]

The link in References for "Well-Known Text (WKT) Format, MySQL documentation" https://dev.mysql.com/doc/refman/5.7/en/gis-wkt-format.html no longer leads to the format document. Perhaps it should be http://dev.mysql.com/doc/refman/5.7/en/gis-data-formats.html#gis-wkt-format — Preceding unsigned comment added by 2601:9:640:5C:553B:B62C:6C1:9AB6 (talk) 16:00, 23 September 2014 (UTC)

MULTIPOINT example is incorrect[edit]

There have been numerous attempts to fix the incorrect MULTIPOINT:

MULTIPOINT (10 40, 40 30, 20 20, 30 10)

All attempts have been reverted! Why?

It is not valid according the OGC specs:

1) OGC 05-126 Version: 1.1.0

<MultiPoint Tagged Text> := MULTIPOINT <Multipoint Text>
<Multipoint Text> := EMPTY | ( <Point Text > {, <Point Text > }* )
<Point Text> := EMPTY | ( <Point> )
<Point> := <x> <y>

2) OGC 06-103 Version: 1.2.[0-1]

<multipoint tagged text> ::= multipoint <multipoint text>
<multipoint text> ::= <empty set>
        | <left paren> <point text> {<comma> <point text>}* <right paren>
<point text> ::= <empty set> | <left paren> <point> <right paren>
<point> ::= <x> <y>

Related discussion on PostGIS mailing list: WKT form(s) of MULTIPOINT

--Mloskot (talk) 16:00, 4 December 2013 (UTC)

Both forms are presented in the example, but there should be a footnote to identify which one is described in the standards (OpenGIS, then OGC, then SQL/MM). The other form (without excessive parenthesis) is very common among various software, so I wouldn't suggest it is "incorrect". +mt 19:31, 5 December 2013 (UTC)
Well-Known Text (WKT) is a name of format forged by OGC, not some general term for parenthesis-wrapped tagged lists of coordinates. The fact that some software handle degenerate form of format is no reason to display it in the article devoted to OGC Well-Known Text. Any non-standard implementation-specific variant should be simple removed or moved to dedicated section clearly labelled as non-standard behaviours. The history why degenerate form is supported, like in PostGIS, is quite funny and due to bug in examples of the early version of specification document. So, the degenerate MULTIPOINT form as presented is incorrect, there should be no doubt. --Mloskot (talk) 14:31, 9 December 2013 (UTC)

TIN example is incorrect[edit]

According to OGC SFS 1.2+, the current example

TIN (((0 0 0, 0 0 1, 0 1 0, 0 0 0)), ((0 0 0, 0 1 0, 1 1 0, 0 0 0)))

should read, either

TIN Z (((0 0 0, 0 0 1, 0 1 0, 0 0 0)), ((0 0 0, 0 1 0, 1 1 0, 0 0 0)))

or

TIN (((0 0, 0 0, 0 1, 0 0)), ((0 0, 0 1, 1 1, 0 0)))