Execute requests seem to be wrong

[gfenoy]

Describe the bug
We can see in the available execute request example (https://schemas.opengis.net/wps/2.0/xml-examples/wpsExecuteRequestExample.xml) that the Data block is defined differently that in the ETS examples used as request templates (https://github.com/opengeospatial/ets-wps20/tree/main/src/main/resources/org/opengis/cite/wps20/examples).

In the official schemas.opengis.net, we have the following:

<wps:Input id="DISTANCE">
  <wps:Data>10.0</wps:Data>
</wps:Input>

In the ETS example, we have for instance, the following:

<wps:Input id="example.input.id">
  <wps:Data>
    <wps:LiteralValue>hello_literal</wps:LiteralValue>
  </wps:Data>
</wps:Input>

This extra LiteralValue block seems to be necessary to the default instance to work, but we don't see any in the official example.

To Reproduce
Deploy the ETS using docker

Expected behavior
The ETS should use Execute requests without extra block such as LiteralValue and ComplexData which are not defined in table 23 just after the figure 16.

[ghobona]

Figure 16 specifies that <wps:Data> accepts any payload. The XSD also states the same, by virtue of extending <extension base="anyType">.

The XSD also states that "This element is used to embed the data in a WPS request or response. The content can be XML data, plain character data, or specially encoded binary data (i.e. base64). "

Therefore the Execute requests sent by the ETS are correct as per the Standard and the XSD.

[gfenoy]

xmllint command reports that there is an issue with ComplexData, please, see bellow.

xmllint --schema "http://schemas.opengis.net/wps/2.0/wpsExecute.xsd" Echo_Process_Complex.xml
<?xml version="1.0"?>
<wps:Execute xmlns:wps="http://www.opengis.net/wps/2.0" xmlns:ows="http://www.opengis.net/ows/2.0" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" mode="sync" response="raw" service="WPS" version="2.0.0" xsi:schemaLocation="http://www.opengis.net/wps/2.0 http://schemas.opengis.net/wps/2.0/wps.xsd">
    <ows:Identifier>echo</ows:Identifier>
	  <wps:Input id="b">
        <wps:Data>
            <wps:ComplexData>
                <testElement>hello_complex</testElement>
            </wps:ComplexData>
        </wps:Data>
    </wps:Input>
    <wps:Output id="b" transmission="value"/>
</wps:Execute>
Echo_Process_Complex.xml:14: element testElement: Schemas validity error : Element 'testElement': This element is not expected. Expected is ( {http://www.opengis.net/wps/2.0}Format ).
Echo_Process_Complex.xml fails to validate

When the following validates.

xmllint --schema "http://schemas.opengis.net/wps/2.0/wpsExecute.xsd" FixedEcho_Process_Complex.xml
<?xml version="1.0"?>
<wps:Execute xmlns:wps="http://www.opengis.net/wps/2.0" xmlns:ows="http://www.opengis.net/ows/2.0" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" mode="sync" response="raw" service="WPS" version="2.0.0" xsi:schemaLocation="http://www.opengis.net/wps/2.0 http://schemas.opengis.net/wps/2.0/wps.xsd">
    <ows:Identifier>echo</ows:Identifier>
	  <wps:Input id="b">
        <wps:Data>
                <testElement>hello_complex</testElement>
        </wps:Data>
    </wps:Input>
    <wps:Output id="b" transmission="value"/>
</wps:Execute>
FixedEcho_Process_Complex.xml validates

For the LiteralData it is a bit different. Indeed the two versions validate. Please, see bellow examples.

xmllint --schema "http://schemas.opengis.net/wps/2.0/wpsExecute.xsd" Echo_Process_Literal.xml
<?xml version="1.0" encoding="UTF-8"?>
<wps:Execute xmlns:wps="http://www.opengis.net/wps/2.0" xmlns:ows="http://www.opengis.net/ows/2.0" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" mode="sync" response="raw" service="WPS" version="2.0.0" xsi:schemaLocation="http://www.opengis.net/wps/2.0 http://schemas.opengis.net/wps/2.0/wps.xsd">
    <ows:Identifier>echo</ows:Identifier>
	  <wps:Input id="a">
        <wps:Data>
            <wps:LiteralValue>hello_literal</wps:LiteralValue>
        </wps:Data>
    </wps:Input>
	  <wps:Output id="a" transmission="value"/>
</wps:Execute>
Echo_Process_Literal.xml validates

But this version also validates.

xmllint --schema "http://schemas.opengis.net/wps/2.0/wpsExecute.xsd" FixedEcho_Process_Literal.xml
<?xml version="1.0" encoding="UTF-8"?>
<wps:Execute xmlns:wps="http://www.opengis.net/wps/2.0" xmlns:ows="http://www.opengis.net/ows/2.0" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" mode="sync" response="raw" service="WPS" version="2.0.0" xsi:schemaLocation="http://www.opengis.net/wps/2.0 http://schemas.opengis.net/wps/2.0/wps.xsd">
    <ows:Identifier>echo</ows:Identifier>
	  <wps:Input id="a">
        <wps:Data>hello_literal</wps:Data>
    </wps:Input>
	  <wps:Output id="a" transmission="value"/>
</wps:Execute>
FixedEcho_Process_Literal.xml validates

Nevertheless, I would add that in this case, only the second version of the request means that you are passing the string "hello_literal". In the first version of the request, you are passing the value <wps:LiteralValue>hello_literal</wps:LiteralValue> which looks odd value for a string. Also, as the ETS is then searching for the string "hello_literal" rather than the previously mentioned string value, it leads to normal failure of the test.

[ghobona]

@gfenoy You are correct regarding hello_literal. The code in Line#140 appears to be only looking for the value of the string. The ETS will be updated to fix the issue.

The <wps:ComplexData> issue needs some further research.

[gfenoy]

<wps:ComplexData> should be used in ProcessDescription, I cannot recall any other use of it in WPS 2.0.0.

In our implementation, we return an invalid XML file as a result (using the wps namespace which is not defined).

In case we remove this block, we make the request validate against the XSD, which is a requirement.

[gfenoy]

The XSD also states that "This element is used to embed the data in a WPS request or response. The content can be XML data, plain character data, or specially encoded binary data (i.e. base64). "

In case you are willing to use XML data, you are allowed to do so. Nevertheless, when you include the extra <wps:ComplexData> block, it means you add it as the root node of the XML data. It makes your node content (extracted from the initial XML, with no namespace definition included) not valid once returned as-is (raw). Implementers can easily solve this specifically for the echo service and remove the <wps:ComplexData> from the corresponding output, but I don't think it is a requirement to do so to be a compliant WPS implementation.

[ghobona]

Since the literal value check only checks for the string hello_literal in the response there is no need to change that part of the code.

However, the complex data check needed to be modified to ensure that the Execute request was passed xml validation. This has now been done through PR #35