1. and perspectives for AIXM
WFS status
and perspectives for AIXM
Alain Hubert -
Director of Research & Development
Ionic Software
September 2007

2. Content
Overview of WFS spec
Application domains
WFS and neo-geography
OGC/ISO and specification process
Next steps for WFS (1.2)
WFS and AIXM
Conclusions
References

3. Introduction to Web Feature Service
Whereas Web Map Service delivers a map image, the OGC® Web Feature Service (WFS) implementation Specification supports the direct exploitation and access of feature data and associated attributes on the Web.
The WFS is a service interface that describes data manipulation on geographic features. Data Manipulation operations include the ability to insert, delete, update, get and query features on spatial and non-spatial constraints
The XML-based GML furnishes the default payload-encoding for transporting the geographic features, but other formats like shapefiles can also serve for transport.

4. What are Features ?
A feature is "an abstraction of a real world phenomenon; it is a geographic feature if it is associated with a location relative to the Earth”. It can be a real world object (a tree, a POI), an observation or an event (accident, fire)
A Feature is an instance of a feature type
A Feature Type defines the structure of the Features. It is defined by a set of attributes that have a name and a type. The attributes can be numbers, strings, dates, etc. but also a geometry that localizes the features on the earth or even another feature.
A Feature Collection is a set of features. It is a kind of feature that groups other features.

5. Main WFS operations WFS WFST
GetCapabilities - Indicates which feature types it can service and what operations are supported on each.
DescribeFeatureType - Describes the structure of any feature type upon request.
GetFeature - Services requests to retrieve feature instances from a datastore. Feature properties to fetch may be specified. The query may be constrained spatially and non-spatially.
LockFeature - Processes a lock request on one or more instances of a feature type for the duration of a transaction. This ensures that serializable transactions are supported.
Transaction - Services transaction requests. A transaction request is composed of operations that modify features in the datastore; insert, update and delete features.
WFS
WFST

6. OGC/ISO and specification process
WFS is an Open Geospatial Consortium specification. Current version is WFS 1.1. Current work on version 1.2.
WFS / ISO is a committee draft, in edition at ISO/TC 211.

7. WFS-Simple
The WFS Simple mission is to specify a common, minimal feature set for geospatial-temporal data queries on the Web.
A primary goal is to encourage databases with basic location information (like lat/long coordinates), to support location-aware queries. Most mainstream Web systems, like blogging engines and standard PHP/MySQL setups, should be able to easily add WFS Simple functionality by supporting two standardized parameters, BBOX and TIME, in queries.
Ex:
Primary differences with WFS:
GML is not a required output format
There is no HTTP POST encoding of a WFS Simple request
Only one Feature Type is allowed per service instance (therefore the TypeName parameter goes away)
Queries are specified using regex instead of a <Filter> parameter
Query support is optional (this applies to WFS also, but it is important to emphasize)

8. Other neo-geographic trends
GeoRSS ( is a simple proposal for geo-enabling, or tagging, "really simple syndication" (RSS) feeds with location information.
GeoJSON JSON (JavaScript Object Notation) is a lightweight computer data interchange format. It is a text-based, human-readable format for representing simple data structures and associative arrays (called objects). GeoJSON geo-enables JSON.

9. Active WFS (notifications) Temporal operations Improved query model
Next steps for WFS (1.2)
Long transactions
Active WFS (notifications)
Temporal operations
Improved query model
Discussions on history/versioning
Improved SOAP binding

10. National mapping agencies (GML updates, data ordering)
Application domains
National mapping agencies (GML updates, data ordering)
Interoperable SDIs (e-Gov)
Complex data queries (enterprise solutions)
Secured vector data access (Defense)

11. Base further data access applications on standard service layer
WFS and AIXM
Use standardized data/geometry model (GML) and access service (WFS) in order to provide a standard-based and stable AIXM service architecture
Base further data access applications on standard service layer
AIXM schema based on GML 3.2
A WFS can serve such schema

12. WFS and AIXM
The returned feature collection from the WFS can be heterogeneous (multiple feature types)
Transactions (in WFS 1.1) should be done on features. Timeslices cannot be currently updated independantly. Timeslice is an array, each timeslice item cannot be addressed. (but loose spec, and therefore implementation could allow that) (coming work on WFS 1.2 will improve the transaction model)
WFS supports GET/POST & SOAP (strong bindings guidelines currently on the way at OGC)

13. Conclusions AIXM 5 is a profile of GML 3.2
Data in that profile can be served by a WFS
Usual AIXM operations can be applied to a WFS
Complexity of AIXM schemas should be investigated in order to simplify data access
Transactions are made difficult due to Timeslice array
WFS improvements at OGC and ISO are on their way
Inputs, such AIXM work, is very important for adaptings specs like WFS to real-world uses
By its very dynamic nature, AIXM data (multi sites, lots of changes, …) is a perfect candidate for integration into OGC SDIs

14. References OGC: http://www.opengeospatial.org
ISO TC211:
WFS WG:
Next OGC meetings:
Boulder (Colorado, USA) – Sep 17
Stresa (Italy) – Dec 10 (tentative)

15. Thank you for your attention
Alain Hubert