At the abstract level, the Definitions component is just a container for two categories of component; WSDL components and type system components.

WSDL components are interfaces, bindings and services.

Type system components are element declarations and type definitions drawn from some type system. The former define the [local name], [namespace name], [children] and [attributes] properties of an element information item; the latter define only the [children] and [attributes] properties.

The properties of the Definitions component are as follows:

The set of interfaces/binding/services/etc. available in the Definitions component include those that are defined within the component itself and those that are imported and/or included. At the component model level, there is no distinction between directly defined components vs. imported/included components.

The components directly defined within a single Definitions component are said to belong to the same target namespace. The target namespace therefore groups a set of related component definitions and provides a hint of the intended semantics of the components.

Imported components have different target namespace values from the Definitions component that is importing them. Thus importing is the mechanism to use components from one namespace in another set of definitions.

Each WSDL or type/element component 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 kids 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.

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

WSDL definitions are represented in XML by one or more WSDL Information Sets (Infosets), that is one or more definitions element information items. A WSDL Infoset contains representations for a collection of WSDL components which share a common target namespace. A WSDL Infoset which contains one or more import element information items corresponds to a collection with components drawn from multiple target namespaces.

The target namespace represents an unambiguous name for the intended semantics of the WSDL Infoset. The targetNamespace URI SHOULD point to a human or machine processable document that directly or indirectly defines the semantics of the WSDL Infoset.

The definitions element information item has the following Infoset properties:

The mapping between the properties of the Definitions component (see ) and the XML Representation of the definitions element information item (see ) is described in .

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

An interface can optionally extend one or more other interfaces. In such cases the interface contains the operations of the interfaces it extends, along with any operations it defines. The interfaces a given interface extends MUST NOT themselves extend that interface either directly or indirectly.

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 definitions container the combination of {name} and {target namespace} properties must be unique.

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

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

An Interface Operation component describes an operation that a given interface supports. An operation is an interaction with the service consisting of a set (ordinary and fault) messages exchanged between the service and the other roles involved in the interaction, in particular the service requester. The sequencing and cardinality of the messages involved in a particular interaction is governed by the message exchange pattern used by the operation (see {message exchange pattern} property).

A message exchange pattern defines placeholders for messages, the participants in the pattern (i.e., the sources and sinks of the messages), and the cardinality and sequencing of messages exchanged by the participants. The message placeholders are associated with specific message types by the operation using the pattern via message and fault references (see {message references} and {fault references} properties). The service whose operation is using the pattern becomes one of the participants of the pattern. This specification does not define a machine understandable language for defining message exchange patterns nor does it define any specific patterns. The companion specification, defines a set of such patterns and defines identifying URIs any of which MAY be used as the value of the {message exchange pattern} property.

The properties of the Interface Operation component are as follows:

Interface Operation components are local to Interface components; they cannot be referred to by QName, despite having both {name} and {target namespace} properties. That is, this specification does not preclude one from having two distinct Interface Operation components which have the same {name} and {target namespace} properties, as long as they are in different Interface components (with the same {target namespace} property).

For each Interface Operation component in the {operations} property of an Interface component the combination of {name} and {target namespace} properties must be unique.

In cases where, due to an interface extending one or more other interfaces, two or more Interface Operation components have the same value for their {name} and {target namespace} properties, then the component models of those Interface Operation components MUST be equivalent (see ). If the Interface Operation components are equivalent then they are considered to collapse into a single component. It is an error if two Interface Operation components have the same value for their {name} and {target namespace} properties but are not equivalent.

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

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

A Message Reference component associates XML element declarations that define the message content for one of the messages participating in an operation.

Message Reference components are identified by the role the message plays in the {message exchange pattern} that the operation is using. That is, a message exchange pattern defines a set of placeholder messages that participate in the pattern and assigns them unique names within the pattern. The purpose of a Message Reference component is to associate an actual message type (XML element declaration for message content) for the message that will perform a specific role in the message exchange pattern.

The properties of the Message Reference component are as follows:

For each Message Reference component in the {message references} property of an Interface Operation component the {message reference} property MUST be unique.

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

The mapping between the properties of the Message Reference component (see ) and the XML Representation of the message reference element information item (see ) is as described in .

A Fault Reference component associates an XML element declaration that defines the fault message contents for a fault that occurs related to a message participating in an operation.

Fault Reference components are identified by the role the related message plays in the {message exchange pattern} that the operation is using. That is, a message exchange pattern defines a set of placeholder messages that participate in the pattern and assigns them unique names within the pattern. The purpose of a Fault Reference component is to associate an actual message type (XML element declaration) for the fault that will occur related to a specific message in the message exchange pattern.

The companion specification defines two fault patterns that a given message exchange pattern may use. For the pattern fault-replaces-message, the message that the fault relates to identifies the message in place of which the declared fault message will occur. Thus, the fault message will travel in the same direction as the message it replaces in the pattern. For the pattern message-triggers-fault, the message that the fault relates to identifies the message after which the indicated fault may occur, in the opposite direction of the referred to message. That is, the fault message will travel in the opposite direction of the message it comes after in the pattern.

More than one Fault Reference component may refer to the same message role. This allows one to indicate that there is more than one type of fault that is related to that message.

The properties of the Fault Reference component are as follows:

If two or more Interface Operation components in the same Interface component have Fault Reference components with the same {name} value, then their {message} properties MUST have the same value. This allows two or more operations to indicate that they both produce the same fault.

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

The mapping between the properties of the Fault Reference component (see ) and the XML Representation of the message reference element information item (see ) is as described in .

A feature component describes an abstract piece of functionality typically associated with the exchange of messages between communicating parties. Although WSDL poses no constraints on the potential scope of such features, examples might include "reliability", "security", "correlation", and "routing". The presence of a feature component in a WSDL description indicates that the feature is either accepted or required in particular interactions.

Features in the Feature component are identified by their URI. Unless otherwise specified, recognizing a feature's URI is assumed to be semantically equivalent to understanding the feature's specification.

The properties of the Feature component are as follows:

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

The mapping between the properties of the Feature component (see ) and the XML Representation of the feature element information item (see ) is as described in .

A Property component describes the set of possible values for a particular property. The permissible values are specified by references to a Schema description. A property is typically used to control a feature's behavior. Properties, and hence property values, can be shared amongst features.

The properties of the Property component are as follows:

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

The mapping between the properties of the Property component (see ) and the XML Representation of the property element information item (see ) is as described in .

A Binding component describes a concrete message format and transmission protocol which may be used to define an endpoint (see ). Binding components can be used to describe such information in a re-usable manner for any interface or specifically for a given interface. Furthermore, binding information MAY be specified on a per-operation basis (see ) within an interface in addition to across all operations of an interface.

If a Binding component specifies operation-specific binding details (by including Binding Operation components) then it MUST specify an interface the Binding component applies to to indicate which interface the operations come from.

Conversely, a Binding component MAY omit any operation-specific binding details and MAY omit specifying an interface. Binding components that do not specify an interface MAY be used to specify operation-independent binding details for Service components with different interfaces.

No concrete binding details are given in this specification. The companion specification, WSDL (Version 2.0): Bindings defines such bindings for SOAP 1.2 , HTTP and MIME . Other specifications MAY define additional binding details. Such specifications are expected to annotate the Binding component (and its sub-components) with additional properties and specify the mapping between those properties and the XML representation.

Bindings are named constructs and can be referred to by QName (see ). For instance, Endpoint components refer to bindings in this way.

The properties of the Binding component are as follows:

For each Binding component in the {bindings} property of a definitions container, the combination of {name} and {target namespace} properties must be unique.

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

The mapping between the properties of the Binding component (see ) and the XML Representation of the binding element information item (see ) is as described in .

A Binding Operation component describes a concrete binding for a particular operation of an interface to a particular concrete message format. A particular operation of an interface is uniquely identified by the target namespace of the interface and the name of the operation within that interface.

The properties of the Binding Operation component are as follows:

The tuple of properties {name} and {target namespace} identify the operation for which binding information is being specified.

For each Binding Operation component in the {operations} property of a Binding component the combination of {name} and {target namespace} properties must be unique. That is, one cannot define multiple bindings for the same operation.

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

The mapping between the properties of the Binding Operation component (see ) and the XML Representation of the binding element information item (see ) is as described in .

A Binding Message Reference component describes a concrete binding for a particular message participating in an operation to a particular concrete message format.

The properties of the Binding Message Reference component are as follows:

For each Binding Message Reference component in the {message references} property of a Binding Operation component the {message reference} property must be unique. That is, the same message cannot be bound twice within the same operation.

The XML representation for a Binding Message Reference component is an element information item with the following Infoset properties:

The mapping between the properties of the Binding Message Reference component (see ) and the XML Representation of the binding element information item (see ) is as described in .

A Binding Fault Reference component describes a concrete binding of a particular fault message of an operation to a particular concrete message format.

The properties of the Binding Fault Reference component are as follows:

For each Binding Fault Reference component in the {message references} property of a Binding Operation component the {message reference} property must be unique. That is, the same fault message cannot be bound twice within the same operation.

The XML representation for a Binding Fault Reference component is an element information item with the following Infoset properties:

The mapping between the properties of the Binding Fault Reference component (see ) and the XML Representation of the binding element information item (see ) is as described in .

A Service component describes a set of endpoints (see ) at which the single interface of the service is provided. The endpoints thus are in effect alternate places at which the service is provided.

Service are named constructs and can be referred to by QName (see ).

The properties of the Service component are as follows:

For each Service component in the {services} property of a definitions container, the combination of {name} and {target namespace} properties MUST be unique.

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

The mapping between the properties of the Service component (see ) and the XML Representation of the service element information item (see ) is as described in .

An Endpoint component defines the particulars of a specific endpoint at which a given service is available.

Endpoint components are local to a given Service component; they cannot be referred to by QName.

The properties of the Endpoint component are as follows:

For each Endpoint component in the {endpoints} property of a Service component, the {binding} property (see ) MUST either be a Binding component with an unspecified {interface} property (see or a Binding component with an {interface} property equal to the {interface} property of the Service component.

For each Endpoint component in the {endpoints} property of a Service component the {name} property must be unique.

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

The mapping between the properties of the Endpoint component (see ) and the XML Representation of the endpoint element information item (see ) is as described in .

Importing an XML Schema uses the xs:import mechanism defined by XML Schema ,, with its syntax and semantics, plus some restrictions. The schema components defined in the imported schema are available for reference by QName (see ). Note that only components defined in the schema itself and components included by it via xs:include are available to WSDL. Specifically components that the schema imports via xs:import are NOT available to WSDL.

A child element information item of the types element information item is defined with the Infoset properties as follows:

Embedding an XML schema uses the existing top-level xs:schema element information item. It may be viewed as simply cutting and pasting an existing, stand-alone schema, to a location inside the types element information item. The schema components defined in the embedded schema are available to WSDL for reference by QName (see ). Note that only components defined in the schema itself and components included by it via xs:include are available to WSDL. Specifically components that the schema imports via xs:import are NOT available to WSDL.

The xs:schema element information item has the following Infoset properties:

Whether embedded or imported, the element declarations present in a schema may be referenced from a Message Reference or Fault Reference component.

A named, global xs:element declaration may be referenced from the message attribute information item of an input or output element information item. The QName is constructed from the targetNamespace of the schema and the content of the name attribute information item of the xs:element element information item. A message attribute information item may not refer to an xs:simpleType or an xs:complexType element information item.

Similarly, a named, global xs:simpleType or xs:complexTypedefinition may be referenced by QName. The QName is constructed from the targetNamespace of the schema and the content of the name attribute information item of the xs:simpleType or xsd:complexTypeelement information item.

The location attribute information item has the following Infoset properties:

A location attribute information item is of type xs:anyURI. Its actual value is the location of some information for the namespace identified by the targetNamespace attribute information item of the containing definitions element information item.

The actual value of the targetNamespace attribute information item of the included WSDL document MUST match the actual value of the targetNamespace attribute information item of the definitions element information item which is the [parent] of the include element information item.

The namespace attribute information item has the following Infoset properties:

The namespace attribute information item is of type xs:anyURI. Its actual value indicates that the containing WSDL document MAY contain qualified references to WSDL definitions in that namespace (via one or more prefixes declared with namespace declarations in the normal way). This value MUST NOT match the actual value of the enclosing WSDL document targetNamespace attribute information item. If the import statement results in the import of a WSDL document then the actual value of the namespace attribute information item MUST be identical to the actual value of the imported WSDL document's targetNamespace attribute information item.

The location attribute information item has the following Infoset properties:

The location attribute information item is of type xs:anyURI. Its actual value is the location of some information for the namespace identified by the namespace attribute information item.

The location attribute information item is optional to allow WSDL components to be constructed from information other than serialized XML 1.0 and to allow for WSDL processors that have a priori knowledge of certain namespaces.

Extension elements can be marked as mandatory by annotating them with a wsdl:required attribute information item (see ) with a value of true. Mandatory extensions are those that MUST be processed correctly by the WSDL processor. If a mandatory extension element is processed, the WSDL processor MUST either agree to fully abide by all the rules and semantics signaled by the extension element's qualified name, or immediate cease processing (fault). In particular, if the WSDL processor does not recognize the qualified name of the extension element, it MUST fault. If the WSDL processor recognizes the qualified name, and determines that the extension in question is incompatible with any other aspect of the document (including other required extensions), it MUST fault.

WSDL provides a global attribute information item with the following Infoset properties:

The type of the required is xs:boolean.