1. Modernizing web service standards: The next version of WFS
Clemens Portele
Editor of WFS 3.0, Part 1

2. ISO 19142:2010 / OGC Web Feature Service 2.0
Key characteristics, strong points:
Access to spatial databases over HTTP – read and write
Fine-grained access to spatial data – by feature or even by property
Full support for GML application schemas
Advanced queries via Filter Encoding (ISO 19143:2010)
Very powerful – supports many advanced use cases
Captures community requirements collected over the last 20 years
Issues, weak points:
Architecture was bleeding edge 20 years ago, but is outdated today and not consistent with the architecture of the Web
Significant initial investment required to understand and implement WFS as a server or client
Feature-rich, modular structure hard to understand
Too many OGC/WFS-specific concepts
Strong reliance on XML (Capabilities, Filter Encoding, GML) and XML Schema
A database interface without considerations for access control

3. ISO 19142:2010 / OGC Web Feature Service 2.0
Key characteristics, strong points:
Access to spatial databases over HTTP – read and write
Fine-grained access to spatial data – by feature or even by property
Full support for GML application schemas
Advanced queries via Filter Encoding (ISO 19143:2010)
Very powerful – supports many advanced use cases
Captures community requirements collected over the last 20 years
Issues, weak points:
Architecture was bleeding edge 20 years ago, but is outdated today and not consistent with the architecture of the Web
Significant initial investment required to understand and implement WFS as a server or client
Feature-rich, modular structure hard to understand
Too many OGC/WFS-specific concepts
Strong reliance on XML (Capabilities, Filter Encoding, GML) and XML Schema
A database interface without considerations for access control

4. Conclusions for the revision of WFS/FES (ISO 19142/19143)
Build on the knowledge about the community requirements, but modernize the architecture, align it with the current practices on the Web – break free of technological and documentation legacy
Modularize the standards into multiple parts – part 1, the “core”, should specify a simple interface to access spatial data that is already sufficient for many use cases
Remove dependency to XML and XML Schema – in fact, remove dependency to any particular encoding and relax requirements for validation against a schema, at least in the core
Where possible, replace WFS/FES-specific resources and re-use existing resources that Web developers are familiar with and which are supported by libraries that are freely available
Support services that are secured
Use a developer-driven process, do not standardize anything that has not been proven to be useful and developer-friendly – in client and server implementations
 WFS 3.0 is intended to be simpler and more modern, but still an evolution from the previous versions and their implementations

5. Background: W3C/OGC Spatial Data on the Web Best Practices

6. OpenAPI – replaces Capabilities in WFS 3
OpenAPI – replaces Capabilities in WFS 3.0 Supports security, code-generation and more

7. Web architecture: Hypermedia driven, conform to HTTP, support for HTML, …

8. Encodings: Rules for HTML, GeoJSON, GML – all optional

9. WFS 3.0, Part 1: Resource overview
Content Information
WFS 3.0
(JSON, XML, HTML)
WFS Service Capabilities
OpenAPI 3.0
(JSON, YAML, HTML)
Feature Collection
WFS GeoJSON/GML-SF
(GeoJSON, GML, HTML)
Feature
GeoJSON, GML-SF
(GeoJSON, GML, HTML)

10. Development of the new version using a public GitHub repository

11. Encodings
Some examples for cases that are out-of-scope of GeoJSON are:
When solids are used a geometries (e.g. in a 3D city model),
Geometries that include non-linear curve interpolations that cannot be simplified (e.g., use of arcs in authoritative geometries),
Geometries have to be represented in a coordinate reference system that is not based on WGS 84 longitude/latitude (e.g. an authoritative national reference system),
Features have more than one geometric property.

12. Status and plans WFS 3.0, Part 1: Draft available
One implementation available, one in progress
Review by the joint ISO/OGC working group during November 2017
Finalize this revision cycle of the draft in December 2017
Then: wider review, implementation and feedback
Release candidate based on implementation feedback in late 2018
Additional parts:
Depending on the progress and community interest, work on additional parts supporting transactions, more complex queries, etc. could start in early 2018
Some parts should be mature enough in 2018 to verify modularization approach

13. Process considerations for ISO projects 19142 and 19143
Current situation:
ISO 19142:2010 and ISO 19143:2010 are single part standards
Scope of current work items assumes new editions would be single part standards
Potential approach:
Re-scope existing Work Item for ISO to the scope of part 1 of WFS 3.0
Additional parts would then be submitted as NWIPs
ISO would only be revised once (more complex) queries are specified
Once the new edition is approved, the previous edition (i.e., WFS 2.0) is no longer available!
Alternative approach:
Cancel the current Work Items and keep ISO and ISO as they are
Standardize WFS/FES 3.0 as a new multi-part standard with a new 191xx number
Time limits for the ISO stages need to be taken into account
!!! Mention work on 2.x