Logical Operators

The power of combination

In previous chapters we learned how to do different attributive and spatial queries.

Let's combine them by using Logical Operators.

OR

Let's start with the OR-Operator (logical disjunction).

We will use the parking decks-WFS provided by Hanseatic City of Hamburg we already used in Comparison Operators.

Parameter	Value
WFS URL	https://qs-geodienste.hamburg.de/HH_WFS_Verkehr_opendata?SERVICE=WFS
Version	2.0.0
Features Types	verkehr_parkhaeuser
Max Features	leave blank
xmlns	de.hh.up="https://registry.gdi-de.org/id/de.hh.up"
	preise (de) = fees (en) kostenlos (de) = free of charge (en) keine Gebühr (de) = no charge (en)

The services provides an attribute called "preise", i.e. fees.

First, we will look for all parking decks, which can be used free of charge (kostenlos), at least for some time (half an hour or an hour).

The word "kostenlos" occurs in different mixtures like

• 1. Stunde kostenlos|2. Stunde 1,20 EUR | jede weitere Std. 1,50 EUR|Tageshöchstsatz k. A.

• 1. Stunde kostenlos|jede weitere Std. 1,50 EUR|Tageshöchstsatz 15,00 EUR

• halbe Stunde: kostenlos|2. halbe Stunde: 0,50 EUR|2. Stunde: 1,00 EUR| (...)

Remember what we learned in Comparison Operators about Wildcards using the PropertyIsLike-Operator.

<fes:Filter
	xmlns:fes="http://www.opengis.net/fes/2.0"
	xmlns:de.hh.up="https://registry.gdi-de.org/id/de.hh.up">
		<fes:PropertyIsLike wildCard='*' singleChar='.' escapeChar='!'>
			<fes:ValueReference>de.hh.up:preise</fes:ValueReference>
			<fes:Literal>*kostenlos*</fes:Literal>
		</fes:PropertyIsLike>
</fes:Filter>

Using this filter expression, the service will return 5 features (at the time of publication of this chapter):

• 10047 Elbe Einkaufszentrum (EEZ)

• 10076 Alstertal Einkaufszentrum (AEZ) Ost

• 10094 Harburg Carree

• 10116 Alstertal Einkaufszentrum (AEZ) Mitte

• 10117 Alstertal Einkaufszentrum (AEZ) West

Next, we will look for all parking decks with no charges (keine Gebühren) using the well-known PropertyIsEqualTo-Operator.

<fes:Filter
	xmlns:fes="http://www.opengis.net/fes/2.0"
	xmlns:de.hh.up="https://registry.gdi-de.org/id/de.hh.up">
		<fes:PropertyIsEqualTo>
			<fes:ValueReference>de.hh.up:preise</fes:ValueReference>
			<fes:Literal>keine Gebühren</fes:Literal>
		</fes:PropertyIsEqualTo>
</fes:Filter>

The WFS will return 3 additional features:

• 10089 Sander Markt

• 10090 Frascatiplatz

• 10091 Lohbrügger Marktplatz

Instead of sending two separate (disjoined) requests, we can combine them into one single request using the OR-Operator as shown below:

<fes:Filter
	xmlns:fes="http://www.opengis.net/fes/2.0"
	xmlns:de.hh.up="https://registry.gdi-de.org/id/de.hh.up">
	<fes:Or>
		<fes:PropertyIsLike wildCard='*' singleChar='.' escapeChar='!'>
			<fes:ValueReference>de.hh.up:preise</fes:ValueReference>
			<fes:Literal>*kostenlos*</fes:Literal>
		</fes:PropertyIsLike>
		<fes:PropertyIsEqualTo>
			<fes:ValueReference>de.hh.up:preise</fes:ValueReference>
			<fes:Literal>keine Gebühren</fes:Literal>
		</fes:PropertyIsEqualTo>
	</fes:Or>
</fes:Filter>

The only simple trick is to embrace your expressions (to be precise, the conditions within the expression) by the logical operator needed, i.e.

OR
    CONDITION 1
    CONDITION 2
    ...
/OR

AND
    CONDITION 1
    CONDITION 2
    ...
/AND

If you're a programmer, this may be unfamiliar for you because you normally connect conditions by logical operators like this:

CONDITION 1 OR CONDITION 2 OR CONDITION 3

So please keep in mind: logical operators embrace conditions within filter expressions.

AND

Recapitulating what we have learned, using other logical operators is really easy:

• take two or more filter expressions

• make sure, that they are working stand-alone (please test them!)

• combine them by enclosing them by logical operators

To do so, we will have a look at the AND-Operator (logical conjunction) using a mining-WFS provided by Federal State of Brandenburg.

Parameter	Value
WFS URL	https://inspire.brandenburg.de/services/bergbau_wfs? (mining)
Version	2.0
Features Types	bgberechtig (mining rights)
Max Features	leave blank
xmlns	fes="http://www.opengis.net/fes/2.0" app="http://www.deegree.org/app"
	inhaber (de) = holder (en) bodenschatz_kurz (de) = resource, abbr. (en) Ton (de) = clay (en)

First, we want to get all mining rights in Brandenburg owned by the company called "BVVG Bodenverwertungs- und -verwaltungs GmbH".

<fes:Filter
    xmlns:fes="http://www.opengis.net/fes/2.0"
    xmlns:app="http://www.deegree.org/app">
	<fes:PropertyIsEqualTo>
		<fes:ValueReference>app:inhaber</fes:ValueReference>
		<fes:Literal>BVVG Bodenverwertungs- und -verwaltungs GmbH</fes:Literal>
	</fes:PropertyIsEqualTo>
</fes:Filter>

The WFS will return 35 polygon features.

Next, we're interested in all clay pits.

<fes:Filter
    xmlns:fes="http://www.opengis.net/fes/2.0"
    xmlns:app="http://www.deegree.org/app">
	<fes:PropertyIsEqualTo>
		<fes:ValueReference>app:bodenschatz_kurz</fes:ValueReference>
		<fes:Literal>Ton</fes:Literal>
	</fes:PropertyIsEqualTo>
</fes:Filter>

We will get 29 polygon features.

If we want to see only the clay pits owned by BVVG, we have to put all of this together using the AND-Operator.

<fes:Filter
    xmlns:fes="http://www.opengis.net/fes/2.0"
    xmlns:app="http://www.deegree.org/app">
   <fes:And>
	<fes:PropertyIsEqualTo>
		<fes:ValueReference>app:inhaber</fes:ValueReference>
		<fes:Literal>BVVG Bodenverwertungs- und -verwaltungs GmbH</fes:Literal>
	</fes:PropertyIsEqualTo>
	<fes:PropertyIsEqualTo>
		<fes:ValueReference>app:bodenschatz_kurz</fes:ValueReference>
		<fes:Literal>Ton</fes:Literal>
	</fes:PropertyIsEqualTo>
   </fes:And>
</fes:Filter>

The WFS will return 7 polygon features.

Good to know #4

You may ask yourself: is it possible to combine both

1. Comparison Operators

2. Spatial Operators

???

The answer is: yes, it is possible!

To demonstrate it, just copy the BBOX-Expression from BBOX

<fes:Filter
	xmlns:fes="http://www.opengis.net/fes/2.0"
	xmlns:gml="http://www.opengis.net/gml/3.2">
  <fes:BBOX>
        <gml:Envelope srsName="urn:ogc:def:crs:EPSG::25832">
          <gml:lowerCorner>367441.62 5620100.532</gml:lowerCorner>
          <gml:upperCorner>367619.15 5620254.767</gml:upperCorner>
       </gml:Envelope>
   </fes:BBOX>
</fes:Filter>

Next, create a PropertyIsLike-Expression like this

<fes:Filter 
   xmlns:fes="http://www.opengis.net/fes/2.0"
   xmlns:cp="http://inspire.ec.europa.eu/schemas/cp/4.0">
   <fes:PropertyIsLike wildCard='*' singleChar='.' escapeChar='!'>
      <fes:ValueReference>cp:nationalCadastralReference</fes:ValueReference>
      <fes:Literal>054302026*</fes:Literal>
   </fes:PropertyIsLike>
</fes:Filter>

Check, if both expressions are running stand-alone.

If so, please combine them using the AND-Operator:

<fes:Filter 
   xmlns:fes="http://www.opengis.net/fes/2.0"
   xmlns:cp="http://inspire.ec.europa.eu/schemas/cp/4.0">
   <fes:And>
   <fes:PropertyIsLike wildCard='*' singleChar='.' escapeChar='!'>
      <fes:ValueReference>cp:nationalCadastralReference</fes:ValueReference>
      <fes:Literal>054302026*</fes:Literal>
   </fes:PropertyIsLike>
   <fes:BBOX>
        <gml:Envelope srsName="urn:ogc:def:crs:EPSG::25832">
          <gml:lowerCorner>367441.62 5620100.532</gml:lowerCorner>
          <gml:upperCorner>367619.15 5620254.767</gml:upperCorner>
       </gml:Envelope>
   </fes:BBOX>
   </fes:And>
</fes:Filter>

What's the difference?

See for yourself!

Original BBOX

BBOX combined with attribute filter