[Requests] comments: OGC GeoPackage Implementation Standard

Edzer Pebesma edzer.pebesma at uni-muenster.de
Wed Feb 6 11:09:56 EST 2013


PART A

1. Evaluators:
	Institute for Geoinformatics, Univ. Muenster, 52°North
	Edzer Pebesma, Christoph Stasch, Christian Autermann,
		Daniel Nüst
	email: edzer.pebesma at uni-muenster.de

2. Submission:
12-128r1
OpenGIS® GeoPackage Implementation Specification (GPKG)


PART B

1. Requirement: Figure 2
2. Implementation Specification Section number: 7
3. Criticality: Minor
4. Comments/justifications for changes:

geopackage_contents: max_y should be REAL, not BLOB in Figure 2

=====================================================================

1. Requirement: General
2. Implementation Specification Section number: [General, #]
3. Criticality: Major
4. Comments/justifications for changes:

The document has a general mix of model and encodings. For example, 
manifest and metadata are bound to specific encodings (i.e. XML).
Instead, different encodings of a model such as JSON or plain text 
should be allowed and further defined in application profiles. 
Especially mobile systems, which are referenced in the motivation, are 
often not based on XML for good reasons.

=====================================================================

1. Requirement: [General, #]
2. Implementation Specification Section number: 7
3. Criticality: Major
4. Comments/justifications for changes:

There are several srid entries in different tables of the model, e.g. 
geopackage_contents, geometry_columns, raster_columns, etc. It remains 
unclear, how these different srid entries are related to each other. For 
example, does an srid entry in the geometry_columns table overwrite the 
srid of the geopackage_contents entry? Does it need to be consistent? 
This needs to be clarified in the document.

=====================================================================

1. Requirement: General
2. Implementation Specification Section number: General
3. Criticality: Major
4. Comments/justifications for changes:

Introduce facility for specific modelling of time.
Geopackage should accomodate infrastructure in the metadata tables that 
refers to time properties of records. For instance, just like the 
geometry_columns points out where geometries are found, a 
temporal_columns meta-data table should, if present, point out where the 
time information is to be found.

Can repeated measurements and time series be stored in geopackage?

=====================================================================

1. Requirement: General
2. Implementation Specification Section number: General
3. Criticality: Major
4. Comments/justifications for changes:

Explain the role of the reference implementation. Why is that part of 
the specification? Some parts of the reference implementation seem to be 
normative for the specification.
What is the provenance for SpatiaLite? How large is the developer base 
currently? How does the project currently handle extensions offered by 
third parties?

=====================================================================

1. Requirement: General
2. Implementation Specification Section number: General
3. Criticality: Major
4. Comments/justifications for changes:

The specification misses the relations to other OGC standards (e.g. O&M, 
SOS, WFS, WCS,WMS,WMTS, FilterEncoding). Some questions that come into mind:
- Should/can data modelled in O&M be stored in a Geopackage?
- Tiling: What is the relation to WMTS?
- Should services like a WFS also be able to return GeoPackages?

-- 
Edzer Pebesma
Institute for Geoinformatics (ifgi), University of Münster
Weseler Straße 253, 48151 Münster, Germany. Phone: +49 251
8333081, Fax: +49 251 8339763  http://ifgi.uni-muenster.de
http://www.52north.org/geostatistics      e.pebesma at wwu.de



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