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UID:pretalx-foss4g-2022-H7ZEBF@talks.staging.osgeo.org
DTSTART;TZID=CET:20220825T120000
DTEND;TZID=CET:20220825T123000
DESCRIPTION:In Postgis Topology a merge of two surfaces does not involve sp
 atial operations\, since \nthe surface to border relation has foreign key 
 structures in the database. This means that the border of the new object i
 s spatially not touched/changed when two surfaces are merged. With simple 
 feature the common border must be computed on the fly\, which again may in
 volve snapTo and cause tiny overlaps and gaps. \n\nWith Postgis Topology y
 ou can easily make an API where the client only sends new borders which is
  a key issue to secure data integrity. This secures that old border are no
 t are not moved by a client error or the by simple transport format\, beca
 use existing points are never not passed back to the server. Postgis Topol
 ogy makes it easy for the server to work with those new borders(delta)\, b
 ecause there are standard methods for this in Postgis Topology and all rel
 ations between border and surfaces are stored in the database. Postgis Top
 ology also has validation routines in addition to using standard database 
 constraints to secure a healthy system. \n\nThe principles that Postgis To
 pology is based on was used in spatial system many years ago\, but one pro
 blem was to keep the border line work nice and clean and not end up in a s
 paghetti.  So one of the first things we did together with Sandro Santilli
  was to create methods on top of Postgis Topology to avoid this\, by throw
 ing away any border parts that does not contribute to a new “valid” su
 rface.\n\nPostgis Topology is built on a relational database model that is
  based on SQL-MM part 3. Your own domain data are easily linked to border\
 , surface objects with more. For instance to check domain attributes on a 
 surface on the other side of a border is not spatial query but a standard 
 relational query. \n\nThe following projects will also be touched in this 
 talk:\n\nhttps://gitlab.com/nibioopensource/pgtopo_update_sql (Functions u
 sing Postgis Topology to make it easy to create spatial update clients.)\n
 \nhttps://github.com/strk/qgis_pgis_topoedit (Postgis Topology is very wel
 l integrated with QGIS.)\n\nhttps://github.com/larsop/resolve-overlap-and-
 gap (Show how we clean up\,  simplify\, generalize  simple feature tables 
 with millions of rows using Postgis Topology)\n\nIs relational database st
 ructure a good choice for Postgis Topology? Yes I will mean and since it
 ’s also linked up SQL-MM part3 and not a random private structure and wi
 th all great Postgis functions available this is very good combination. Yo
 u may take take glance at https://www.ibm.com/ibm/history/ibm100/us/en/ico
 ns/reldb/ and other articles about relational databases. \n\nThe plan now 
 is to build a full ecosystem around Postgis Topology with a generic client
  to support declarative rules\, where you can define attributes\, rules fo
 r attribute handling and how to deal with overlap and gap. \n\nAll the wor
 k NIBIO has done/is doing here would not have been possible with out the g
 reat support from Sandro Santilli.
DTSTAMP:20260403T215359Z
LOCATION:Room Limonaia
SUMMARY:Postgis Topology to secure data integrity\, simple API and clean up
  messy simple feature datasets. - Lars Opsahl\, sandro santilli\, Mattia N
 atali
URL:https://talks.staging.osgeo.org/foss4g-2022/talk/H7ZEBF/
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