Hello Stefano, so here is my case:

The Datasource definition as is in the web.xml is working fine,I am listing it below just to have something to compare.

<web-app xmlns="http://java.sun.com/xml/ns/javaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
         version="3.0">
    <data-source>
        <name>java:jboss/datasources/testpostgre</name>
        <class-name>org.postgresql.xa.PGXADataSource</class-name>
        <server-name>localhost</server-name>
        <database-name>papodb</database-name>
        <user>papo</user>
        <password>papo</password>
        <transactional>true</transactional>
    </data-source>
</web-app>

The postgresql driver I am actually loading from my pom (see above)

postgresql:postgresql9.1-901-1.jdbc4

My ds.xml file is the following- I think the drivers tag is not valid, if this is true, then according to the note in the documentation you can not deploy a datasource on the fly referencing a driver at same time? By the way some examples or notes on the 1_1 xsd would help (in the documentation).

<datasources xmlns="http://www.jboss.org/ironjacamar/schema"
             xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
             xsi:schemaLocation="http://www.jboss.org/ironjacamar/schema http://docs.jboss.org/ironjacamar/schema/datasources_1_1.xsd">
<datasource jndi-name="java:jboss/datasources/testpostgre" pool-name="testpostgre" enabled="true" use-java-context="true">
    <connection-url>jdbc:postgresql://localhost:5432/papodb</connection-url>
    <driver>postgresql</driver>
    <security>
        <user-name>papo</user-name>
        <password>papo</password>
    </security>
    <driver-class>org.postgresql.xa.PGXADataSource</driver-class>
    <!-- the drivers tag is not valid with this XSD-->
    <drivers>
        <driver>
            <driver name="postgresql" module="org.postgresql">
                <xa-datasource-class>org.postgresql.xa.PGXADataSource</xa-datasource-class>
            </driver>
        </driver>
    </drivers>
</datasource>
</datasources>

Many thanks!

My case was unit tests using arquillian. I wanted to decouple the DS definition from code or annotations and leverage (if it works) the ability to package one extra file, which can me altered using maven properties prior to deployment.

Hi, I think there is no outcome, it seems that Wildfly 8.1 does not support my case as, indicated in my original post. You can use workarounds (like I did, defining the DS in an JavaEE descriptio (ear or war level).