[postgis-devel] WKT form(s) of MULTIPOINT

Mateusz Loskot mateusz at loskot.net
Wed Dec 4 07:31:20 PST 2013


Hi,

Yet another curiosity from the OGC vs PostGIS ring.
Given the WKT BNF grammars specified in the two versions of OGC SFS:

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>

Why PostGIS documentation shows MULTIPOINT(0 0,1 2)
as example in "OpenGIS WKB and WKT"?
(PostGIS can parse the degenerate form as well.)

BTW, Wikipedia [1] also shows the same form (after PostGIS?):
http://en.wikipedia.org/wiki/Well-known_text

I sense, this is due to *incorrect* example presented in 6.2.3 section
of the OGC 05-126 Version: 1.1.0,
where ‘MULTIPOINT (10 10, 20 20)’ is presented.

Which version of OGC SF does PostGIS implement here?

Best regards,
-- 
Mateusz  Łoskot, http://mateusz.loskot.net


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