Can a WSDL indicate the SOAP version (1.1 or 1.2) of the web service?

Is it possible to see if a web service uses SOAP 1.1 or 1.2, based on the information in the WSDL?

SOAP 1.1 uses namespace http://schemas.xmlsoap.org/wsdl/soap/

SOAP 1.2 uses namespace http://schemas.xmlsoap.org/wsdl/soap12/

The wsdl is able to define operations under soap 1.1 and soap 1.2 at the same time in the same wsdl. Thats useful if you need to evolve your wsdl to support new functionality that requires soap 1.2 (eg. MTOM), in this case you dont need to create a new service but just evolve the original one.

In WSDL, if you look at the Binding section, you will clearly see that soap binding is explicitly mentioned if the service uses soap 1.2. refer the below sample.

<binding name="EmployeeServiceImplPortBinding" type="tns:EmployeeServiceImpl">
<soap12:binding transport="http://schemas.xmlsoap.org/soap/http" style="document"/>
<operation name="findEmployeeById">
    <soap12:operation soapAction=""/>
    <input><soap12:body use="literal"/></input>
    <output><soap12:body use="literal"/></output>
</operation><operation name="create">
    <soap12:operation soapAction=""/>
    <input><soap12:body use="literal"/></input>
    <output><soap12:body use="literal"/></output>
</operation>
</binding>

if the web service use soap 1.1, it will not explicitly define any soap version in the WSDL file under binding section. refer the below sample.

<binding name="EmployeeServiceImplPortBinding" type="tns:EmployeeServiceImpl">
<soap:binding transport="http://schemas.xmlsoap.org/soap/http" style="rpc"/>
<operation name="findEmployeeById">
    <soap:operation soapAction=""/>
    <input><soap:body use="literal" namespace="http://jaxb.ws.jax.samples.chathurangaonline.com/"/></input>
    <output><soap:body use="literal" namespace="http://jaxb.ws.jax.samples.chathurangaonline.com/"/></output>
</operation><operation name="create">
    <soap:operation soapAction=""/>
    <input><soap:body use="literal" namespace="http://jaxb.ws.jax.samples.chathurangaonline.com/"/></input>
    <output><soap:body use="literal" namespace="http://jaxb.ws.jax.samples.chathurangaonline.com/"/></output>
</operation>
</binding>

How to determine the SOAP version of the SOAP message?

but remember that this is not much recommended way to determine the soap version that your web services uses. the version of the soap message can be determined using one of following ways.

1. checking the namespace of the soap message

SOAP 1.1  namespace : http://schemas.xmlsoap.org/soap/envelope

SOAP 1.2 namespace  : http://www.w3.org/2003/05/soap-envelope

2. checking the transport binding information (http header information) of the soap message

SOAP 1.1 : user text/xml for the Context-Type

   POST /MyService HTTP/1.1
   Content-Type: text/xml; charset="utf-8"
   Content-Length: xxx
   SOAPAction: "urn:uuid:myaction"

SOAP 1.2 : user application/soap+xml for the Context-Type

   POST /MyService HTTP/1.1
   Content-Type: application/soap+xml; charset="utf-8"
   Content-Length: xxx
   SOAPAction: "urn:uuid:myaction"

3. using SOAP fault information

The structure of a SOAP fault message between the two versions are different.

I have found this page

http://schemas.xmlsoap.org/wsdl/soap12/soap12WSDL.htm

which says that Soap 1.2 uses the new namespace http://schemas.xmlsoap.org/wsdl/soap12/

It is in the 'WSDL 1.1 Binding extension for SOAP 1.1'.

Yes you can usually see what SOAP version is supported based on the WSDL.

Take a look at Demo web service WSDL. It has a reference to the soap12 namespace indicating it supports SOAP 1.2. If that was absent then you'd probably be safe assuming the service only supported SOAP 1.1.

Found transport-attribute in binding-element which tells us that this is the WSDL 1.1 binding for the SOAP 1.1 HTTP binding.

ex.

<wsdlsoap:binding style="document" transport="http://schemas.xmlsoap.org/soap/http"/>