Thanks David for pointing out the wrong points.

I made some tries, and figure out a sample datasource for mysql:
<ext-module>
        <connector>mysqlxads</connector>
        <external-path xmlns:dep="http://geronimo.apache.org/xml/ns/deployment-1.2">
            <dep:groupId>org.tranql</dep:groupId>
            <dep:artifactId>tranql-connector-mysql-xa</dep:artifactId>
            <dep:type>rar</dep:type>
        </external-path>
    <connector xmlns="http://geronimo.apache.org/xml/ns/j2ee/connector-1.2">   
    <resourceadapter>
        <outbound-resourceadapter>
            <connection-definition>
                <connectionfactory-interface>javax.sql.DataSource</connectionfactory-interface>
                <connectiondefinition-instance>
                    <name>jdbc/mysqlxads</name>
                    <config-property-setting name="DatabaseName">sampledb</config-property-setting>
                    <config-property-setting name="UserName">theusername</config-property-setting>
                    <config-property-setting name="Password">thepassword</config-property-setting>
                    <connectionmanager>
                        <xa-transaction>
                            <transaction-caching/>
                        </xa-transaction>
                        <single-pool>
                            <max-size>10</max-size>
                            <min-size>0</min-size>
                            <match-one/>
                        </single-pool>
                    </connectionmanager>
                </connectiondefinition-instance>
            </connection-definition>
        </outbound-resourceadapter>
    </resourceadapter>
  </connector>
</ext-module>

As to MS SQL sample, updated as following:
<resourceadapter>
        <outbound-resourceadapter>
            <connection-definition>
                <connectionfactory-interface>
javax.sql.DataSource</connectionfactory-interface>
                <connectiondefinition-instance>
                    <name>jdbc/SampleDatasource</name>
                    <config-property-setting name="UserName">username</config-property-setting>
                    <config-property-setting name="Password">password</config-property-setting>
                    <config-property-setting name="Driver">com.microsoft.sqlserver.jdbc.SQLServerDriver</config-property-setting>
                    <config-property-setting name="ConnectionURL">jdbc:sqlserver://servername:1433;DataBaseName=sampledb</config-property-setting>
                    <connectionmanager>
                        <local-transaction/>
                        <single-pool>
                            <max-size>5</max-size>
                            <min-size>0</min-size>
                            <blocking-timeout-milliseconds>5000</blocking-timeout-milliseconds>
                            <idle-timeout-minutes>15</idle-timeout-minutes>
                            <match-one/>
                        </single-pool>
                    </connectionmanager>
                </connectiondefinition-instance>
            </connection-definition>
        </outbound-resourceadapter>
    </resourceadapter>

Thanks for pointing out any error.