The keywords “MUST”, “MUST NOT”, “REQUIRED”, “SHALL”, “SHALL NOT”, “SHOULD”, “SHOULD NOT”, “RECOMMENDED”, “MAY”, and “OPTIONAL” in this document are to be interpreted as described in RFC 2119 .

Namespace names of the general form:

represent application or context-dependent URIs .

This specification uses the XML Schema type xs:anyURI (see ). It is defined so that xs:anyURI values are essentially IRIs (see ). The conversion from xs:anyURI values to an actual URI is via an escaping procedure defined by (see ), which is identical in most respects to IRI Section 3.1 (see ).

For interoperability, WSDL authors are advised to avoid the US-ASCII characters: "<", ">", '"', space, "{", "}", "|", "\", "^", and "`", which are allowed by the xs:anyURI type, but disallowed in IRIs.

This specification uses predefined namespace prefixes throughout; they are given in the following list. Note that the choice of any namespace prefix is arbitrary and not semantically significant (see ).

This section describes the terms and concepts introduced in Part 1 of the WSDL Version 2.0 specification (this document).

This specification refers to properties in the XML Information Set . Such properties are denoted by square brackets, e.g. [children], [attributes].

This specification defines and refers to properties in the WSDL 2.0 Component Model . Such properties are denoted by curly brackets, e.g. name, interfaces.

This specification uses a consistent naming convention for component model properties that refer to components. If a property refers to a required or optional component, then the property name is the same as the component name. If a property refers to a set of components, then the property name is the pluralized form of the component name.

Z Notation was used in the development of this specification. Z Notation is a formal specification language that is based on standard mathematical notation. The Z Notation for this specification has been verified using the Fuzz 2000 type-checker .

Since Z Notation is not widely known, it is not included the normative version of this specification. However, it is included in a non-normative version which allows to dynamically hide and show the Z Notation. Browsers correctly display the mathematical Unicode characters, provided that the required fonts are installed. Mathematical fonts for Mozilla Firefox can be downloaded from the Mozilla Web site.

The Z Notation was used to improve the quality of the normative text that defines the Component Model, and to help ensure that the test suite covered all important rules implied by the Component Model. However, the Z Notation is non-normative, so any conflict between it and the normative text is an error in the Z Notation. Readers and implementers may nevertheless find the Z Notation useful in cases where the normative text is unclear.

There are two elements of Z Notation syntax that conflict with the notational conventions described in the preceding sections. In Z Notation, square brackets are used to introduce basic sets, e.g. [ID], which conflicts with the use of square brackets to denote XML Information Set properties . Also, in Z Notation, curly brackets are used to denote set display and set comprehension, e.g. {1, 2, 3}, which conflicts with the use of curly brackets to denote WSDL 2.0 Component Model properties . However, the intended meaning of square and curly brackets should be clear from their context and this minor notational conflict should not cause any confusion.

Pseudo-schemas are provided for each component, before the description of the component. They use BNF-style conventions for attributes and elements: ? denotes optionality (i.e. zero or one occurrences), * denotes zero or more occurrences, + one or more occurrences, [ and ] are used to form groups, and | represents choice. Attributes are conventionally assigned a value which corresponds to their type, as defined in the normative schema. Elements with simple content are conventionally assigned a value which corresponds to the type of their content, as defined in the normative schema. Pseudo schemas do not include extension points for brevity.

Assertions about WSDL 2.0 documents and components that are not enforced by the normative XML schema for WSDL 2.0 are marked by a dagger symbol (†) at the end of a sentence. Each assertion has been assigned a unique identifier that consists of a descriptive textual prefix and a unique numeric suffix. The numeric suffixes are assigned sequentially and never reused so there may be gaps in the sequence. The assertion identifiers MAY be used by implementations of this specification for any purpose, e.g. error reporting.

The assertions and their identifiers are summarized in section .

At a high level, the Description component is just a container for two categories of components: WSDL 2.0 components and type system components.

WSDL 2.0 components are interfaces, bindings and services. Type system components are element declarations and type definitions.

Type system components describe the constraints on a message's content. By default, these constraints are expressed in terms of the , i.e. they define the [local name], [namespace name], [children] and [attributes] properties of an element information item. Type systems based upon other data models are generally accommodated by extensions to WSDL 2.0; see . In the case where they define information equivalent to that of a XML Schema global element declaration, they can be treated as if they were such a declaration.

This specification does not define the behavior of a WSDL 2.0 document that uses multiple schema languages for describing type system components simultaneously.

An Element Declaration component defines the name and content model of an element information item such as that defined by an XML Schema global element declaration. It has a name property that is the QName of the element information item and a system property that is the namespace IRI of the extension element information items for the type system, e.g. the namespace of XML Schema.

A Type Definition component defines the content model of an element information item such as that defined by an XML Schema global type definition. It has a name property that is the QName of the type and a system property that is the namespace IRI of the extension element information items for the type system, e.g. the namespace of XML Schema.

Interface, Binding, Service, Element Declaration, and Type Definition components are directly contained in the Description component and are referred to as top-level components. The top-level WSDL 2.0 components contain other components, e.g. Interface Operation and Endpoint, which are referred to as nested components. Nested components may contain other nested components. The component that contains a nested component is referred to as the parent of the nested component. Nested components have a parent property that is a reference to their parent component.

The properties of the Description component are as follows:

The set of top-level components contained in the Description component associated with an initial WSDL 2.0 document consists of the components defined in the initial document, plus the components associated with the WSDL 2.0 documents that the initial document includes, plus the components defined by other WSDL 2.0 documents in the namespaces that the initial document imports. The component model makes no distinction between the components that are defined in the initial document versus those that are defined in the included documents or imported namespaces. However, any WSDL 2.0 document that contains component definitions that refer by QName to WSDL 2.0 components that belong to a different namespace MUST contain a wsdl:import element information item for that namespace (see ). Furthermore, all QName references, whether to the same or to different namespaces must resolve to components (see ).

When using the XML Schema language to describe type system components, the inclusion of Element Declaration components and Type Definition components in a Description component is governed by the rules in .

In addition to WSDL 2.0 components and type system components, additional extension components MAY be added via extensibility . Further, additional properties to WSDL 2.0 and type system components MAY also be added via extensibility.

WSDL 2.0 descriptions are represented in XML by one or more WSDL 2.0 Information Sets (Infosets), that is one or more description element information items. A WSDL 2.0 Infoset contains representations for a collection of WSDL 2.0 components that share a common target namespace and zero or more wsdl:import element information items that correspond to a collection with components from multiple target namespaces.

The components directly defined or included within a Description component are said to belong to the same target namespace. The target namespace therefore groups a set of related component definitions and represents an unambiguous name for the intended semantics of the collection of components. The value of the targetNamespace attribute information item SHOULD be dereferencable. It SHOULD resolve to a human or machine processable document that directly or indirectly defines the intended semantics of those components. It MAY resolve to a WSDL 2.0 document that provides service description information for that namespace.

If a WSDL 2.0 document is split into multiple WSDL 2.0 documents (which may be combined as needed via ), then the targetNamespace attribute information item SHOULD resolve to a master WSDL 2.0 document that includes all the WSDL 2.0 documents needed for that service description. This approach enables the WSDL 2.0 component designator fragment identifiers to be properly resolved.

Components that belong to imported namespaces have different target namespace values than that of the importing WSDL 2.0 document. Thus importing is the mechanism to use components from one namespace in the definition of components from another namespace.

Note that each WSDL 2.0 document or type system component of the same kind must be uniquely identified by its qualified name. That is, if two distinct components of the same kind (Interface, Binding, etc.) are in the same target namespace, then their QNames MUST be unique. However, different kinds of components (e.g., an Interface component and a Binding component) MAY have the same QName. Thus, QNames of components must be unique within the space of those components in a given target namespace.

The description element information item has the following Infoset properties:

The mapping from the XML Representation of the description element information item (see ) to the properties of the Description component is described in .

An Interface component describes sequences of messages that a service sends and/or receives. It does this by grouping related messages into operations. An operation is a sequence of input and output messages, and an interface is a set of operations.

An interface can optionally extend one or more other interfaces. To avoid circular definitions, an interface MUST NOT appear in the set of interfaces it extends, either directly or indirectly. The set of operations available in an interface includes all the operations defined by the interfaces it extends directly or indirectly, together with any operations it directly defines. The operations directly defined on an interface are referred to as the declared operations of the interface. In the process, operation components that are equivalent per are treated as one single component. The interface extension mechanism behaves in a similar way for all other components that can be defined inside an interface, namely Interface Fault components.

Interfaces are named constructs and can be referred to by QName (see ). For instance, Binding components refer to interfaces in this way.

The properties of the Interface component are as follows:

For each Interface component in the interfaces property of a Description component, the name property MUST be unique.

The XML representation for an Interface component is an element information item with the following Infoset properties:

The mapping from the XML Representation of the interface element information item (see ) to the properties of the Interface component is as described in .

Recall that, per , the Interface components in the extended interfaces property of a given Interface component MUST NOT contain that Interface component in any of their extended interfaces properties, that is to say, recursive extension of interfaces is disallowed.

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