# GetCapabilities

Back in the jungle, it would be a good idea to get an overview!

Especially what the WFS you want to use is able to deliver.

I myself didn't pay much attention to the GetCapabilities-Request in the past. 

But the GetCapabilities-document contains really useful information!

So let's explore it.

I'll use the cadastral parcel service of North Rhine-Westphalia subsequently.

It's GetCapabilities-URL is:

```url
https://www.wfs.nrw.de/geobasis/wfs_nw_inspire-flurstuecke_alkis?SERVICE=WFS&REQUEST=GetCapabilities&VERSION=2.0.0
```

If you don't know the GetCapabilities-URL of the WFS you're using, add a **OGC WFS (Web Feature Service)** Reader to your FME Workbench. 

Then open **\[Parameters ...]**, paste the WFS-URL in **\[URL]**, select a **\[Feature Type]** and set **\[Max Features]** to a small number, e.g. like this:

<figure><img src="/files/CphvufwHDXVcxxPqt6yb" alt=""><figcaption></figcaption></figure>

Next **\[Run Just This]**.

<figure><img src="/files/LkPb2YZtH1PdDenJU3TV" alt=""><figcaption></figcaption></figure>

FME sends a request to the service and will get the number of features you specified before.

Now, remember your friend: the Translation Log

Scroll upwards!&#x20;

You'll see some blue colored URLs. We need the **\<WFS> Capabilities URL**.

<figure><img src="/files/JFVN3aW4VObDNwlLEIYq" alt=""><figcaption></figcaption></figure>

Double click or copy & paste it to your browser.

Now we will collect some relevant information.

```xml
<ows:Parameter name="AcceptVersions">
   <ows:AllowedValues>
     <ows:Value>2.0.0</ows:Value>
   </ows:AllowedValues>
</ows:Parameter>
```

**AcceptVersions** tells you, which WFS versions are supported. Other WFS may support more than one version, e.g.

```xml
<ows:Parameter name="AcceptVersions">
   <ows:AllowedValues>
     <ows:Value>2.0.0</ows:Value>
     <ows:Value>1.1.0</ows:Value>
     <ows:Value>1.0.0</ows:Value>
   </ows:AllowedValues>
</ows:Parameter>
```

To know the WFS version is important, because you have to use the corresponding filter expression version! We will have a look at it later.

Generally you should use version 2.0.0 if your WFS supports it.

Next, have a look at **CountDefault**.

```xml
<ows:Constraint name="CountDefault">
   <ows:NoValues/>
   <ows:DefaultValue>100000</ows:DefaultValue>
</ows:Constraint>
```

The WFS 2.0 specification says about it: "*If the server does have a **server** configured **count limit**, that limit shall be advertised in the server's capabilities document using the **CountDefault** constraint.*"

In case of our WFS just try it: set **Max Feature** to nothing and run it.

Result: the WFS returns exactly 100.000 features (approx. 180 MB).

Next scroll down to the section named **FeatureTypeList** and the **FeatureType** you want to use, here **CadastralParcel**:

```xml
<wfs:FeatureTypeList>
<wfs:FeatureType xmlns:cp="http://inspire.ec.europa.eu/schemas/cp/4.0">
<wfs:Name>cp:CadastralParcel</wfs:Name>
<wfs:Title>Flurstück</wfs:Title>
<wfs:Abstract>Gebiete, die anhand des Liegenschaftskatasters oder gleichwertiger Verzeichnisse bestimmt werden.</wfs:Abstract>
<ows:Keywords>
<ows:Keyword>Flurstück</ows:Keyword>
<ows:Keyword>Cadastral Parcel</ows:Keyword>
</ows:Keywords>
<wfs:DefaultCRS>urn:ogc:def:crs:EPSG::25832</wfs:DefaultCRS>
<wfs:OtherCRS>http://www.opengis.net/def/crs/EPSG/0/25832</wfs:OtherCRS>
<wfs:OtherCRS>http://www.opengis.net/def/crs/EPSG/0/25833</wfs:OtherCRS>
<wfs:OtherCRS>http://www.opengis.net/def/crs/EPSG/0/3034</wfs:OtherCRS>
<wfs:OtherCRS>http://www.opengis.net/def/crs/EPSG/0/3857</wfs:OtherCRS>
<wfs:OtherCRS>http://www.opengis.net/def/crs/EPSG/0/4258</wfs:OtherCRS>
<wfs:OtherCRS>http://www.opengis.net/def/crs/EPSG/0/4326</wfs:OtherCRS>
<wfs:OtherCRS>http://www.opengis.net/def/crs/EPSG/0/900913</wfs:OtherCRS>
<wfs:OtherCRS>urn:ogc:def:crs:EPSG::25833</wfs:OtherCRS>
<wfs:OtherCRS>urn:ogc:def:crs:EPSG::3034</wfs:OtherCRS>
<wfs:OtherCRS>urn:ogc:def:crs:EPSG::3857</wfs:OtherCRS>
<wfs:OtherCRS>urn:ogc:def:crs:EPSG::4258</wfs:OtherCRS>
<wfs:OtherCRS>urn:ogc:def:crs:EPSG::4326</wfs:OtherCRS>
<wfs:OtherCRS>urn:ogc:def:crs:EPSG::900913</wfs:OtherCRS>
```

Write down the **DefaultCRS** (Coordinate Reference System)!

It will be relevant when we deal with spatial filters.

Continue scrolling down until you see

1. <[fes:LogicalOperators>](fes:LogicalOperators/)
2. <<fes:ComparisonOperators>>
3. <<fes:SpatialOperators>>

There are many intersting things, but we will focus on these three!

## Comparison Operators

Comparison Operators are the same as you may know using SQL:

```xml
<fes:ComparisonOperators>
   <fes:ComparisonOperator name="PropertyIsEqualTo"/>
   <fes:ComparisonOperator name="PropertyIsNotEqualTo"/>
   <fes:ComparisonOperator name="PropertyIsLessThan"/>
   <fes:ComparisonOperator name="PropertyIsGreaterThan"/>
   <fes:ComparisonOperator name="PropertyIsLessThanOrEqualTo"/>
   <fes:ComparisonOperator name="PropertyIsGreaterThanOrEqualTo"/>
   <fes:ComparisonOperator name="PropertyIsLike"/>
   <fes:ComparisonOperator name="PropertyIsNull"/>
   <fes:ComparisonOperator name="PropertyIsNil"/>
   <fes:ComparisonOperator name="PropertyIsBetween"/>
</fes:ComparisonOperators>
```

* PropertyIsEqualTo means "="
* PropertyIsNotEqualTo means "!="
* PropertyIsLessThan means "<"
* and so on

You guess it!

## Spatial Operators

Spatial Operators may be more interesting:

```xml
<fes:SpatialOperators>
   <fes:SpatialOperator name="BBOX"/>
   <fes:SpatialOperator name="Equals"/>
   <fes:SpatialOperator name="Disjoint"/>
   <fes:SpatialOperator name="Intersects"/>
   <fes:SpatialOperator name="Touches"/>
   <fes:SpatialOperator name="Crosses"/>
   <fes:SpatialOperator name="Within"/>
   <fes:SpatialOperator name="Contains"/>
   <fes:SpatialOperator name="Overlaps"/>
   <fes:SpatialOperator name="Beyond"/>
   <fes:SpatialOperator name="DWithin"/>
</fes:SpatialOperators>
```

I suggest, that you're familiar with spatial operations!?

We will focus on some of them, especially the Bounding Box (BBOX).

## Logical Operators

Using Logical Operators like **AND, OR** and **NOT**, you'll be able to combine two or more of the above operators, i.e.

* attribute with attribute comparisons
* attribute with spatial comparisons

Unfortunately, not all WFS support logical operators. You have to try (and error)!

Wrap it up!&#x20;

Let's practice ...

## Good to know #1

As we're dealing with **metadata**, would it be interesting for you to know the total **number of features in one Feature Type** for example CadastralParcels? (Not the total quantity/sum of all features in different Feature Types a WFS holds available).

Yes?

If so, grab the **GetFeature URL** from the **Translation Log** (will be explained in detail in [The Formula](/filter-expressions-in-fme/the-formula.md#examine-a-feature)), delete anything starting with "*<mark style="color:red;">\&NAMESPACES=xmlns...</mark>*" and replace it by "*<mark style="color:blue;">\&resultType=hits</mark>*" (make sure to keep your Feature Type which is defined in TYPENAMES).

**Caution**: the keyword **resultType** is **case sensitive**!

As a result

```url
https://www.wfs.nrw.de:443/geobasis/wfs_nw_inspire-flurstuecke_alkis?SERVICE=WFS&VERSION=2.0.0&REQUEST=GetFeature&TYPENAMES=cp%3ACadastralParcel&NAMESPACES=xmlns%28cp%2Chttp%3A%2F%2Finspire.ec.europa.eu%2Fschemas%2Fcp%2F4.0%29&OUTPUTFORMAT=application%2Fgml%2Bxml%3B%20version%3D3.2&COUNT=1
```

becomes to

```url
https://www.wfs.nrw.de:443/geobasis/wfs_nw_inspire-flurstuecke_alkis?SERVICE=WFS&VERSION=2.0.0&REQUEST=GetFeature&TYPENAMES=cp%3ACadastralParcel&resultType=hits
```

Open this new URL in your favorite browser, safe and open the returned XML document.

```
<wfs:FeatureCollection
    xmlns:wfs="http://www.opengis.net/wfs/2.0"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation=" http://www.opengis.net/wfs/2.0 http://www.wfs.nrw.de/aaa-suite/schema/ogc/wfs/2.0/wfs.xsd"
    timeStamp="2023-09-08T09:29:20.413+02:00"
    numberReturned="0"
    numberMatched="9359425"
/>
```

You can see, that on September, ninth, there are 9.359.425 cadastral parcel features.


---

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