2.3.1 The Interface Fault
Component
A fault is an event that occurs during the execution of a
message exchange that disrupts the normal flow of messages.
A fault is typically raised when a party is unable to
communicate an error condition inside the normal message flow, or a
party wishes to terminate a message exchange. A fault message may
be used to communicate out of band information such as the reason
for the error, the origin of the fault, as well as other informal
diagnostics such as a program stack trace.
An Interface Fault
component describes a fault that MAY occur during invocation of an
operation of the interface. The Interface Fault component declares
an abstract fault by naming it and indicating the contents of the
fault message. When and how the fault message flows is indicated by
the Interface Operation
component.
The Interface Fault
component provides a clear mechanism to name and describe the set
of faults an interface may generate. This allows operations to
easily identify the individual faults they may generate by name.
This mechanism allows the ready identification of the same fault
occurring across multiple operations and referenced in multiple
bindings as well as reducing duplication of description for an
individual fault.
Note that faults other than the ones described in the Interface component can also be
generated at run-time, i.e. faults are an open set.
The properties of the Interface Fault component are as
follows:
For each Interface Fault
component in the {interface faults}
property of an Interface
component, the {name}
property must be unique.
Interface Fault
components are uniquely identified by the the QName of the
enclosing Interface component
and QName of the Interface
Fault component itself.
Note:
Despite having a {name} property, Interface Fault components cannot
be identified solely by their QName. Indeed, two Interface components whose {name} property value has the same
namespace name, but different local names, can contain Interface Fault components with the
same {name} property
value. Thus, the {name}
property of Interface Fault
component is not sufficient to form the unique identity of an
Interface Fault
component.
In cases where, due to an interface extending one or more other
interfaces, two or more Interface Fault components have the
same value for their {name} property, then the
component models of those Interface Fault components MUST be
equivalent (see 2.17 Equivalence of
Components). If the Interface Fault components are
equivalent then they are considered to collapse into a single
component. It is an error if two Interface Fault components that are
available in the same Interface
component have the same value for their {name} properties but are not
equivalent.
Note that, due to the above rules, if two interfaces that have
the same value for the namespace name of their {name} property also have one or more
faults that have the same value for their {name} property then those two
interfaces cannot both form part of the derivation chain of a
derived interface unless those faults are the same fault.
Note:
For the above reason, it is considered good practice to ensure,
where necessary, that the local name of the {name} property of Interface Fault components within a
namespace are unique, thus allowing such derivation to occur
without inadvertent error.
If a type system NOT based on the XML Infoset [XML Information Set] is in use (as
considered in 3.2 Using Other Schema
Languages) then additional properties would need to be
added to the Interface
Fault component (along with extensibility attributes to its XML
representation) to allow associating such message types with the
message reference.
2.3.2 XML Representation of Interface
Fault Component
<description>
<interface>
<fault
name="xs:NCName"
element="xs:QName"? >
<documentation />*
[ <feature /> | <property /> ]*
</fault>
</interface>
</description>
The XML representation for an Interface Fault component is an
element information item with the following Infoset
properties:
-
A [local name] of fault
-
A [namespace name] of "http://www.w3.org/2005/08/wsdl"
-
One or more attribute information items amongst its
[attributes] as follows:
-
Zero or more element information item amongst its
[children], in order, as follows:
-
Zero or more documentation element information
items (see 5.
Documentation).
-
Zero or more element information items from among the
following, in any order:
2.3.2.1 name
attribute information item with fault [owner
element]
The name attribute information item
identifies a given fault element information
item inside a given interface element
information item.
The name attribute information item has
the following Infoset properties:
The type of the name attribute information
item is xs:NCName.
2.3.2.2 element
attribute information item with fault [owner
element]
The element attribute information item
refers, by QName, to an Element Declaration
component.
The element attribute information item has
the following Infoset properties:
The type of the element attribute information
item is xs:QName.