> For the complete documentation index, see [llms.txt](https://olivers-expression-lab.gitbook.io/filter-expressions-in-fme/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://olivers-expression-lab.gitbook.io/filter-expressions-in-fme/outlook-wfs-3.0.md). # Outlook: WFS 3.0 Jay: Did you ever flashy-thing me? Kay: No. (M.I.B.) If you want/have to deal with **WFS version 3.0** also known as **OGC API – Features**, please forget eveything you ever learned about **XML Filter Expressions**! **Important note: You can NOT use XML Filter Expressions in order to query a WFS 3.0! That's technically impossible.** Normally, this chapter should end here, because filtering an API Features WFS needs a different approach. But as WFS 3.0 is becoming more and more popular, I'll give you some hints, how to use WFS 3.0 with FME. First of all, you'll need a service URL like this: ```url https://ogc-api.nrw.de/lika ``` Please copy and paste this URL into a web browser! The first difference is, that you'll see a GetCapabilities-like document, which is human readable (by default) and not an XML.

Beneath "***Ressources***" please click the first link in order to show the **Collections**. ``` Please note: Collections are the most important concept of WFS 3.0. ``` According to the specification (chpt. 4.1.4) a **feature collection** or **collection** is a set of features from a dataset.

**Collections** are presented the same way. You'll see a (human readable) list of feature types (sets), the service provides, e.g. * Flurstück * Flurstückspunkt * Gebäude, Bauwerk * Katasterbezirk * Nutzung * Nutzung-Flurstück * Verwaltungseinheit

Next, you may click on a feature type (set), let's say "[Flurstück](https://ogc-api.nrw.de/lika/v1/collections/flurstueck/items)", which opens a graphical preview of both 1. Geometry 2. Attributes

Is this relevant for working with WFS 3.0 in FME? To be honest: not really! But another thing is really important working with FME: the URL ```url https://ogc-api.nrw.de/lika/v1/collections/flurstueck/items ``` If you modify the URL the following way ```url https://ogc-api.nrw.de/lika/v1/collections/flurstueck/queryables ``` i.e. by replacing "***items***" with "***queryables***", you'll get a list of attributes you can use for filtering.

So, let's try it! | Key | Value | | -------------------------------------------- | ---------------------------------------- | | OGC API URL | | | *Version* | *3.0* | | Collections | flurstueck (cadastral parcel) | | Queryables | flstkennz | First, we need a different reader: **OGC API - Features (WFS 3.0)**

Next open **\[Parameters ...]** as usual. Expand **\[Constraints]** and click **\[...]** to select a collection.

Please note: if you just want to see a few features for inspecting, you can limit to number of features to read in reader parameters.

Run the reader and examine the features. ## Comparison Operators As mentioned before, it is not necessary/possible to write XML Filter Expressions to do attributive queries. You can define queries via the user interface. Just expand **\[Constraints]**, **\[Collection Query Parameters]**.

In \[**Collection(s)]** you can choose the collections, you've choosen above. In \[**Parameters]** you'll see default parameters predefined by the OGC specification, but unfortunately no service specific parameters, i.e. attributes.

But remember the **Queryables-URL**, which shows a list of attributes you can use for filtering. You can use **any attribute from the Queryables-List** as **Parameter Name**, in this case "**flstkennz**".

Tadaa! You know where we are?

And of course, you can **process a list** as discussed in [Bulk Processing](/filter-expressions-in-fme/bulk-processing.md) by using the **FeatureReader**-Transformer.

## Spatial Operator: BBOX As discussed in [Spatial Operators](/filter-expressions-in-fme/spatial-operators.md#bbox), the bounding box is the swiss army knife of all spatial filters, because you can request a BBOX from the server and do the spatial operation locally in FME subsequently. Also remember the predefined **\[Collection Query Parameters]** we have seen above, especially * **bbox** * **bbox-crs** (**C**oordinate **R**eference **S**ystem) If your service comes in WGS84 (EPSG:4326) as default coordinate system, it is sufficient to pass a **comma seperated coordinate list** to the service (see [spec](https://docs.ogc.org/is/17-069r3/17-069r3.html#_parameter_bbox)): 1. lower left X, 2. lower left Y, 3. upper right X, 4. upper right Y If the default coordinate system ist **not WGS84**, you have to define the coordinate system of your bbox coordinates in **\[bbox-crs].** **Important note:** you have to use the coordinate string provided by **your** service! I.e. you can not use the string, you normally use in FME, e.g. "EPSG:25832".

bbox-crs	result
http://www.opengis.net/def/crs/EPSG/0/25832	works
EPSG:25832	will not work

To summarize:

Parameter Name	Parameter Value
bbox-crs	http://www.opengis.net/def/crs/EPSG/0/25832
bbox	367441,5620100,367619,5620254

Please compare the corresponding result shown in [Spatial Operators](/filter-expressions-in-fme/spatial-operators.md#bbox)! Ok, so far the detour to WFS 3.0. If you want to, you can play around with this: ```url https://ogc-api.nrw.de/gebref/v1/collections/gebref/ ``` ``` id: DENW36HK100076NN ```

**Caution**: please check the coordinates in Inspector ...