Schematron is rule-based validation language. It is different from XML schema validation and it is supplement to XML schema validation. If required you can apply both of them to the validation of the XML document.
Schematron defines a set of assertions that are to be enforced. If all these assertions are met, the document is seen as valid.
The assertion is specified using XPath.
Schematron has 4 key elements: pattern, assert, rule and ns.
The assert element has an attribute of test whose value is defined as XPath expression. This expression should return a Boolean value. If the test expression evaluates to true, then assertion has been met.
The assert is defined within a rule element.
Multiple asserts may be defined in a rule element. Each rule has a context attribute, which also contains an XPath expression used to specify the nodes to which the asserts will be tested.
The context may return zero, one or more nodes from XML document instance. Each node will be tested against all asserts within this rule.
Here is one example:
We need to validate that the MSISDN should start with 04 and totally has
10 digits and CAC should be numeric.
What we do here is to define one patter in which
there are two contexts defined. The
context is using XPath to get the right element in XML document. One context is for MSISDN element and another
for CAC element. In each element there
is one assertion. The assertion contains
the test statement which uses the Regular expression to validate the element
value.
<sch:schema
xmlns:sch="http://www.ascc.net/xml/schematron">
<!-- define the process
namespace for finding the elements in the rule-->
<sch:ns uri="http://toic.com/orderManagement/messages/v1"
prefix="tns"/>
<sch:ns
uri="http://www.oracle.com/XSL/Transform/java/oracle.tip.pc.services.functions.Xpath20"
prefix="xp20"/>
<sch:pattern
name="Check the parameters in ExecuteOrdre request">
<!--
context is the super variable that can be queried for validation-->
<!-- Check
MSISDN as Identification has validate value -->
<sch:rule
context="tns:ExecuteOrderRequest[
xp20:ends-with(@*[local-name()='type'], 'CustomerOrder')
]/tns:Party/tns:PartyRole/tns:Identification[xp20:ends-with(./*[local-name()='Type'],
'MSISDN')] ">
<sch:assert
test="xp20:matches( string(tns:Value), '\b04\d{8}\b')">MSISDN
should be 10 digit numeric starting with 04</sch:assert>
</sch:rule>
<!-- Check CAC
as Identification has validate value -->
<sch:rule
context="tns:ExecuteOrderRequest[
xp20:ends-with(@*[local-name()='type'], 'CustomerOrder')
]/tns:Party/tns:PartyRole/tns:Identification[xp20:ends-with(./*[local-name()='Type'],
'CAC')] ">
<sch:assert
test="xp20:matches( string(tns:Value), '\b\d{1,}$')">CAC should
be numeric</sch:assert>
</sch:rule>
</sch:pattern>
</sch:schema>
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