WSDL is an XML format for describing network services as a set of endpoints operating on
messages containing either document-oriented or procedure-oriented information. The
operations and messages are described abstractly, and then bound to a concrete network
protocol and message format to define an endpoint. Related concrete endpoints are
combined into abstract endpoints (services). WSDL is extensible to allow description of
endpoints and their messages regardless of what message formats or network protocols are
used to communicate, however, the only bindings described in this document describe how
to use WSDL in conjunction with SOAP 1.1, HTTP GET/POST, and MIME.
This document is a submission to the World Wide Web Consortium (see Submission
Request, W3C Staff Comment) as a
suggestion for describing services for the W3C XML
Activity on XML Protocols. For a full list of all acknowledged Submissions,
please see Acknowledged Submissions to W3C.
This draft represents the current thinking with regard to descriptions of services within
Ariba, IBM and Microsoft. It consolidates concepts found in NASSL, SCL, and SDL
(earlier proposals in this space).
This document is a NOTE made available by the W3C for discussion only. Publication of
this Note by W3C indicates no endorsement by W3C or the W3C Team, or any W3C Members.
W3C has had no editorial control over the preparation of this Note. This document is a
work in progress and may be updated, replaced, or rendered obsolete by other documents
at any time.
A list of current W3C technical documents can be found at the Technical
Reports page.
1 Introduction.
1.1 WSDL Document Example
1.2 Notational Conventions
2 Service Definition
2.1 Document Structure
2.1.1 Document Naming and Linking
2.1.2 Authoring Style
2.1.3 Language Extensibility and Binding
2.1.4 Documentation
2.2 Types
2.3 Messages
2.3.1 Message Parts
2.3.2 Abstract vs. Concrete Messages
2.4 Port Types
2.4.1 One-way Operation
2.4.2 Request-response Operation.
2.4.3 Solicit-response Operation
2.4.4 Notification Operation
2.4.5 Names of Elements within an Operation
2.4.6 Parameter Order within an Operation
2.5 Bindings
2.6 Ports
2.7 Services
3 SOAP Binding
3.1 SOAP Examples
3.2 How the SOAP Binding Extends WSDL
3.3 soap:binding
3.4 soap:operation
3.5 soap:body
3.6 soap:fault
3.7 soap:header and soap:headerfault
3.8 soap:address
4 HTTP GET & POST Binding
4.1 HTTP GET/POST Examples
4.2 How the HTTP GET/POST Binding Extends WSDL
4.3 http:address
4.4 http:binding
4.5 http:operation
4.6 http:urlEncoded
4.7 http:urlReplacement
5 MIME Binding
5.1 MIME Binding example
5.2 How the MIME Binding extends WSDL
5.3 mime:content
5.4 mime:multipartRelated
5.5 soap:body
5.6 mime:mimeXml
6 References
A 1 Notes on URIs
A 1.1 XML namespaces & schema locations
A 1.2 Relative URIs
A 1.3 Generating URIs
A 2 Wire format for WSDL examples
A 2.1 Example 1
A 3 Location of Extensibility Elements
A 4 Schemas
A 4.1 WSDL Schema
A 4.2 SOAP Binding Schema
A 4.3 HTTP Binding Schema
A 4.4 MIME Binding Schema
As communications protocols and message formats are standardized in the web community, it
becomes increasingly possible and important to be able to describe the communications in
some structured way. WSDL addresses this need by defining an XML grammar for describing
network services as collections of communication endpoints capable of exchanging
messages. WSDL service definitions provide documentation for distributed systems and
serve as a recipe for automating the details involved in applications communication.
A WSDL document defines services as collections of network endpoints, or
ports. In WSDL, the abstract definition of endpoints and messages
is separated from their concrete network deployment or data format bindings. This allows
the reuse of abstract definitions: messages, which are abstract
descriptions of the data being exchanged, and port types which are
abstract collections of operations. The concrete protocol and data
format specifications for a particular port type constitutes a reusable
binding. A port is defined by associating a network address with a
reusable binding, and a collection of ports define a service. Hence, a WSDL document
uses the following elements in the definition of network services:
- Types- a container for data type definitions using
some type system (such as XSD).
- Message- an abstract, typed definition of the data
being communicated.
- Operation- an abstract description of an action
supported by the service.
- Port Type-an abstract set of operations supported
by one or more endpoints.
- Binding- a concrete protocol and data format
specification for a particular port type.
- Port- a single endpoint defined as a combination of
a binding and a network address.
- Service- a collection of related endpoints.
These elements are described in detail in Section 2. It is important to observe that WSDL
does not introduce a new type definition language. WSDL recognizes the need for rich
type systems for describing message formats, and supports the XML Schemas specification
(XSD) [11] as its canonical type system. However, since it is
unreasonable to expect a single type system grammar to be used to describe all message
formats present and future, WSDL allows using other type definition languages via
extensibility.
In addition, WSDL defines a common binding mechanism. This is used to
attach a specific protocol or data format or structure to an abstract message,
operation, or endpoint. It allows the reuse of abstract definitions.
In addition to the core service definition framework, this specification introduces
specific binding extensions for the following protocols and message formats:
Although defined within this document, the above language extensions are layered on top
of the core service definition framework. Nothing precludes the
use of other binding extensions with WSDL.
1.2 WSDL Document Example
The following example shows the WSDL definition of a simple service
providing stock quotes. The service supports a single operation called
GetLastTradePrice, which is deployed using the SOAP 1.1 protocol over HTTP. The request
takes a ticker symbol of type string, and returns the price as a float. A detailed
description of the elements used in this definition can be found in Section 2 (core
language) and Section 3 (SOAP binding).
This example uses a fixed XML format instead of the SOAP encoding (for an example using
the SOAP encoding, see Example 4).
Example 1 SOAP 1.1 Request/Response via HTTP
<?xml version="1.0"?>
<definitions name="StockQuote"
targetNamespace="http://example.com/stockquote.wsdl"
xmlns:tns="http://example.com/stockquote.wsdl"
xmlns:xsd1="http://example.com/stockquote.xsd"
xmlns:soap="http://schemas.xmlsoap.org/wsdl/soap/"
xmlns="http://schemas.xmlsoap.org/wsdl/">
<types>
<schema targetNamespace="http://example.com/stockquote.xsd"
xmlns="http://www.w3.org/2000/10/XMLSchema">
<element name="TradePriceRequest">
<complexType>
<all>
<element name="tickerSymbol" type="string"/>
</all>
</complexType>
</element>
<element name="TradePrice">
<complexType>
<all>
<element name="price" type="float"/>
</all>
</complexType>
</element>
</schema>
</types>
<message name="GetLastTradePriceInput">
<part name="body" element="xsd1:TradePriceRequest"/>
</message>
<message name="GetLastTradePriceOutput">
<part name="body" element="xsd1:TradePrice"/>
</message>
<portType name="StockQuotePortType">
<operation name="GetLastTradePrice">
<input message="tns:GetLastTradePriceInput"/>
<output message="tns:GetLastTradePriceOutput"/>
</operation>
</portType>
<binding name="StockQuoteSoapBinding" type="tns:StockQuotePortType">
<soap:binding style="document" transport="http://schemas.xmlsoap.org/soap/http"/>
<operation name="GetLastTradePrice">
<soap:operation soapAction="http://example.com/GetLastTradePrice"/>
<input>
<soap:body use="literal"/>
</input>
<output>
<soap:body use="literal"/>
</output>
</operation>
</binding>
<service name="StockQuoteService">
<documentation>My first service</documentation>
<port name="StockQuotePort" binding="tns:StockQuoteBinding">
<soap:address location="http://example.com/stockquote"/>
</port>
</service>
</definitions>
1. 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 [2].
2. The following namespace prefixes are used throughout this document:
| prefix | namespace URI | definition | | wsdl | http://schemas.xmlsoap.org/wsdl/ | WSDL namespace for WSDL framework. | | soap | http://schemas.xmlsoap.org/wsdl/soap/ | WSDL namespace for WSDL SOAP binding. | | http | http://schemas.xmlsoap.org/wsdl/http/ | WSDL namespace for WSDL HTTP GET & POST binding. | | mime | http://schemas.xmlsoap.org/wsdl/mime/ | WSDL namespace for WSDL MIME binding. | | soapenc |
http://schemas.xmlsoap.org/soap/encoding/
| Encoding namespace as defined by SOAP 1.1 [8]. | | soapenv |
http://schemas.xmlsoap.org/soap/envelope/
| Envelope namespace as defined by SOAP 1.1 [8]. | | xsi |
http://www.w3.org/2000/10/XMLSchema-instance
| Instance namespace as defined by XSD [10]. | | xsd |
http://www.w3.org/2000/10/XMLSchema
| Schema namespace as defined by XSD [10]. | | tns | (various) | The "this namespace" (tns) prefix is used as a
convention to refer to the current document. | | (other) | (various) | All other namespace prefixes are samples only. In
particular, URIs starting with "http://example.com" represent some
application-dependent or context-dependent URI [4]. |
3. This specification uses an informal syntax to describe the XML grammar of a
WSDL document:
- The syntax appears as an XML instance, but the values
indicate the data types instead of values.
- Characters are appended to elements and attributes as
follows: "?" (0 or 1), "*" (0 or more), "+"
(1 or more).
- Elements names ending in "..." (such as
<element.../> or <element...>) indicate that elements/attributes
irrelevant to the context are being omitted.
- Grammar in bold has not been introduced earlier in the
document, or is of particular interest in an example.
- <-- extensibility element --> is a placeholder for
elements from some "other" namespace (like ##other in XSD).
- The XML namespace prefixes (defined above) are used to
indicate the namespace of the element being defined.
- Examples starting with <?xml contain enough information
to conform to this specification; others examples are fragments and
require additional information to be specified in order to conform.
XSD schemas are provided as a formal definition of WSDL grammar (see section A4).
2. Service Definition
This section describes the core elements of the WSDL language. Binding extensions for
SOAP, HTTP and MIME are included in Sections 3, 4 and 5.
2.1 WSDL Document Structure
A WSDL document is simply a set of definitions. There is a definitions
element at the root, and definitions inside. The grammar is as follows:
<wsdl:definitions name="nmtoken"? targetNamespace="uri"?>
<import namespace="uri" location="uri"/>*
<wsdl:documentation .... /> ?
<wsdl:types> ?
<wsdl:documentation .... />?
<xsd:schema .... />*
<-- extensibility element --> *
</wsdl:types>
<wsdl:message name="nmtoken"> *
<wsdl:documentation .... />?
<part name="nmtoken" element="qname"? type="qname"?/> *
</wsdl:message>
<wsdl:portType name="nmtoken">*
<wsdl:documentation .... />?
<wsdl:operation name="nmtoken">*
<wsdl:documentation .... /> ?
<wsdl:input name="nmtoken"? message="qname">?
<wsdl:documentation .... /> ?
</wsdl:input>
<wsdl:output name="nmtoken"? message="qname">?
<wsdl:documentation .... /> ?
</wsdl:output>
<wsdl:fault name="nmtoken" message="qname"> *
<wsdl:documentation .... /> ?
</wsdl:fault>
</wsdl:operation>
</wsdl:portType>
<wsdl:binding name="nmtoken" type="qname">*
<wsdl:documentation .... />?
<-- extensibility element --> *
<wsdl:operation name="nmtoken">*
<wsdl:documentation .... /> ?
<-- extensibility element --> *
<wsdl:input> ?
<wsdl:documentation .... /> ?
<-- extensibility element -->
</wsdl:input>
<wsdl:output> ?
<wsdl:documentation .... /> ?
<-- extensibility element --> *
</wsdl:output>
<wsdl:fault name="nmtoken"> *
<wsdl:documentation .... /> ?
<-- extensibility element --> *
</wsdl:fault>
</wsdl:operation>
</wsdl:binding>
<wsdl:service name="nmtoken"> *
<wsdl:documentation .... />?
<wsdl:port name="nmtoken" binding="qname"> *
<wsdl:documentation .... /> ?
<-- extensibility element -->
</wsdl:port>
<-- extensibility element -->
</wsdl:service>
<-- extensibility element --> *
</wsdl:definitions>
Services are defined using six major elements:
- types, which provides data type
definitions used to describe the messages exchanged.
- message, which represents an abstract definition of
the data being transmitted. A message consists of logical parts,
each of which is associated with a definition within some type system.
- portType, which is a set of abstract operations.
Each operation refers to an input message and output messages.
- binding, which specifies concrete protocol and data
format specifications for the operations and messages defined by a
particular portType.
- port, which specifies an address for a binding,
thus defining a single communication endpoint.
- service, which is used to aggregate a set of
related ports.
These elements will be described in detail in Sections 2.2 to 2.7. In the rest of this
section we describe the rules introduced by WSDL for naming documents, referencing
document definitions, using language extensions and adding contextual documentation.
2.1.1 Document Naming and Linking
WSDL documents can be assigned an optional name attribute of
type NCNAME that serves as a lightweight form of documentation. Optionally, a
targetNamespace attribute of type URI may be specified. The URI MUST NOT be a
relative URI.
WSDL allows associating a namespace with a document location using an
import statement:
<definitions .... >
<import namespace="uri" location="uri"/> *
</definitions>
A reference to a WSDL definition is made using a QName. The following types of
definitions contained in a WSDL document may be referenced:
- WSDL definitions: service, port, message, bindings, and
portType
- Other definitions: if additional definitions are added
via extensibility, they SHOULD use QName linking.
Each WSDL definition type listed above has its own name scope (i.e. port names and
message names never conflict). Names within a name scope MUST be unique within the WSDL
document.
The resolution of QNames in WSDL is similar to the resolution of QNames described by the
XML Schemas specification [11].
The use of the import element allows the separation of the different elements of a
service definition into independent documents, which can then be imported as needed.
This technique helps writing clearer service definitions, by separating the definitions
according to their level of abstraction. It also maximizes the ability to reuse service
definitions of all kinds. As a result, WSDL documents structured in this way are easier
to use and maintain. Example 2 below shows how to use this authoring style to define the
service presented in Example 1. Here we separate the
definitions in three documents: data type definitions, abstract definitions, and
specific service bindings. The use of this mechanism is of course not limited to the
definitions explicitly presented in the example, which uses only language elements
defined in this specification. Other types of definitions based on additional language
extensions can be encoded and reused in a similar fashion.
Example 2. Alternative authoring style for the service in Example 1.
http://example.com/stockquote/stockquote.xsd
<?xml version="1.0"?>
<schema targetNamespace="http://example.com/stockquote/schemas"
xmlns="http://www.w3.org/2000/10/XMLSchema">
<element name="TradePriceRequest">
<complexType>
<all>
<element name="tickerSymbol" type="string"/>
</all>
</complexType>
</element>
<element name="TradePrice">
<complexType>
<all>
<element name="price" type="float"/>
</all>
</complexType>
</element>
</schema>
http://example.com/stockquote/stockquote.wsdl
<?xml version="1.0"?>
<definitions name="StockQuote"
targetNamespace="http://example.com/stockquote/definitions"
xmlns:tns="http://example.com/stockquote/definitions"
xmlns:xsd1="http://example.com/stockquote/schemas"
xmlns:soap="http://schemas.xmlsoap.org/wsdl/soap/"
xmlns="http://schemas.xmlsoap.org/wsdl/">
<import namespace="http://example.com/stockquote/schemas"
location="http://example.com/stockquote/stockquote.xsd"/>
<message name="GetLastTradePriceInput">
<part name="body" element="xsd1:TradePriceRequest"/>
</message>
<message name="GetLastTradePriceOutput">
<part name="body" element="xsd1:TradePrice"/>
</message>
<portType name="StockQuotePortType">
<operation name="GetLastTradePrice">
<input message="tns:GetLastTradePriceInput"/>
<output message="tns:GetLastTradePriceOutput"/>
</operation>
</portType>
</definitions>
http://example.com/stockquote/stockquoteservice.wsdl
<?xml version="1.0"?>
<definitions name="StockQuote"
targetNamespace="http://example.com/stockquote/service"
xmlns:tns="http://example.com/stockquote/service"
xmlns:soap="http://schemas.xmlsoap.org/wsdl/soap/"
xmlns:defs="http://example.com/stockquote/definitions"
xmlns="http://schemas.xmlsoap.org/wsdl/">
<import namespace="http://example.com/stockquote/definitions"
location="http://example.com/stockquote/stockquote.wsdl"/>
<binding name="StockQuoteSoapBinding" type="defs:StockQuotePortType">
<soap:binding style="document" transport="http://schemas.xmlsoap.org/soap/http"/>
<operation name="GetLastTradePrice">
<soap:operation soapAction="http://example.com/GetLastTradePrice"/>
<input>
<soap:body use="literal"/>
</input>
<output>
<soap:body use="literal"/>
</output>
</operation>
</binding>
<service name="StockQuoteService">
<documentation>My first service</documentation>
<port name="StockQuotePort" binding="tns:StockQuoteBinding">
<soap:address location="http://example.com/stockquote"/>
</port>
</service>
</definitions>
2.1.3 Language Extensibility and Binding
In WSDL the term binding refers to the process associating protocol or data format
information with an abstract entity like a message, operation, or portType. WSDL allows
elements representing a specific technology (referred to here as extensibility
elements) under various elements defined by WSDL. These points of extensibility
are typically used to specify binding information for a particular protocol or message
format, but are not limited to such use. Extensibility elements MUST use an XML
namespace different from that of WSDL. The specific locations in the document where
extensibility elements can appear are described in detail in section
A3.
Extensibility elements are commonly used to specify some technology specific binding. To
distinguish whether the semantic of the technology specific binding is required for
communication or optional, extensibility elements MAY place a wsdl:required
attribute of type boolean on the element. The default value for required is false.
The required attribute is defined in the namespace
"http://schemas.xmlsoap.org/wsdl/".
Extensibility elements allow innovation in the area of network and message protocols
without having to revise the base WSDL specification. WSDL recommends that
specifications defining such protocols also define any necessary WSDL extensions used
to describe those protocols or formats.
See Sections 3, 4, and 5 for examples of extensibility elements defined as part of the
base WSDL specification.
2.1.4 Documentation
WSDL uses the optional wsdl:document element as a container for human
readable documentation. The content of the element is arbitrary text and elements
("mixed" in XSD). The documentation element is allowed inside any WSDL
language element.
2.2 Types
The types element encloses data type definitions that are relevant for
the exchanged messages. For maximum interoperability and platform neutrality, WSDL
prefers the use of XSD as the canonical type system, and treats it as the intrinsic type
system.
<definitions .... >
<types>
<xsd:schema .... />*
</types>
</definitions>
The XSD type system can be used to define the types in a message regardless of whether or
not the resulting wire format is actually XML, or whether the resulting XSD schema
validates the particular wire format. This is especially interesting if there will be
multiple bindings for the same message, or if there is only one binding but that binding
type does not already have a type system in widespread use. In these cases, the
recommended approach for encoding abstract types using XSD is as follows:
- Use element form (not attribute).
- Don't include attributes or elements that are peculiar to
the wire encoding (e.g. have nothing to do with the abstract content
of the message). Some examples are soap:root, soap:encodingStyle, xmi:id,
xmi:name.
- Array types should extend the Array type defined in the SOAP v1.1
encoding schema (http://schemas.xmlsoap.org/soap/encoding/) (regardless of whether the
resulting form actually uses the encoding specified in Section 5 of the SOAP
v1.1 document). Use the name ArrayOfXXX for array types (where XXX is
the type of the items in the array). The type of the items in the
array and the array dimensions are specified by using a default value for the
soapenc:arrayType attribute. At the time of this writing, the XSD
specification does not have a mechanism for specifying the default value of an
attribute which contains a QName value. To overcome this limitation,
WSDL introduces the arrayType attribute (from namespace
http://schemas.xmlsoap.org/wsdl/) which has the semantic of providing the
default value. If XSD is revised to support this functionality, the
revised mechanism SHOULD be used in favor of the arrayType attribute defined
by WSDL.
- Use the xsd:anyType type to represent a field/parameter which can
have any type.
However, since it is unreasonable to expect a single type system grammar can be used to
describe all abstract types present and future, WSDL allows type systems to be added via
extensibility elements. An extensibility element may appear under the types
element to identify the type definition system being used and to provide an XML
container element for the type definitions. The role of this element can be compared to
that of the schema element of the XML Schema language.
<definitions .... >
<types>
<-- type-system extensibility element --> *
</types>
</definitions>
2.3 Messages
Messages consist of one or more logical parts. Each part is associated with a type
from some type system using a message-typing attribute. The set of message-typing
attributes is extensible. WSDL defines several such message-typing attributes for use
with XSD:
- element. Refers to an XSD element using a QName.
- type. Refers to an XSD simpleType or complexType
using a QName.
Other message-typing attributes may be defined as long as they use a namespace different
from that of WSDL. Binding extensibility elements may also use message-typing
attributes.
The syntax for defining a message is as follows. The message-typing attributes (which
may vary depending on the type system used) are shown in bold.
<definitions .... >
<message name="nmtoken"> *
<part name="nmtoken" element="qname"? type="qname"?/> *
</message>
</definitions>
The message name attribute provides a unique name among all messages defined
within the enclosing WSDL document.
The part name attribute provides a unique name among all the parts of the
enclosing message.
Parts are a flexible mechanism for describing the logical abstract content of a message.
A binding may reference the name of a part in order to specify binding-specific
information about the part. For example, if defining a message for use with RPC, a part
MAY represent a parameter in the message. However, the bindings must be inspected in
order to determine the actual meaning of the part.
Multiple part elements are used if the message has multiple logical units. For example,
the following message consists of a Purchase Order and an Invoice.
<definitions .... >
<types>
<schema .... >
<element name="PO" type="tns:POType"/>
<complexType name="POType">
<all>
<element name="id" type="string/>
<element name="name" type="string"/>
<element name="items">
<complexType>
<all>
<element name="item" type="tns:Item" minOccurs="0" maxOccurs="unbounded"/>
</all>
</complexType>
</element>
</all>
</complexType>
<complexType name="Item">
<all>
<element name="quantity" type="int"/>
<element name="product" type="string"/>
</all>
</complexType>
<element name="Invoice" type="tns:InvoiceType"/>
<complexType name="InvoiceType">
<all>
<element name="id" type="string"/>
</all>
</complexType>
</schema>
</types>
<message name="PO">
<part name="po" element="tns:PO"/>
<part name="invoice" element="tns:Invoice"/>
</message>
</definitions>
However, if the message contents are sufficiently complex, then an alternative syntax may
be used to specify the composite structure of the message using the type system
directly. In this usage, only one part may be specified. In the following example,
the body is either a purchase order, or a set of invoices.
<definitions .... >
<types>
<schema .... >
<complexType name="POType">
<all>
<element name="id" type="string/>
<element name="name" type="string"/>
<element name="items">
<complexType>
<all>
<element name="item" type="tns:Item" minOccurs="0" maxOccurs="unbounded"/>
</all>
</complexType>
</element>
</all>
</complexType>
<complexType name="Item">
<all>
<element name="quantity" type="int"/>
<element name="product" type="string"/>
</all>
</complexType>
<complexType name="InvoiceType">
<all>
<element name="id" type="string"/>
</all>
</complexType>
<complexType name="Composite">
<choice>
<element name="PO" minOccurs="1" maxOccurs="1" type="tns:POType"/>
<element name="Invoice" minOccurs="0" maxOccurs="unbounded" type="tns:InvoiceType"/>
</choice>
</complexType>
</schema>
</types>
<message name="PO">
<part name="composite" type="tns:Composite"/>
</message>
</definitions>
Message definitions are always considered to be an abstract definition of the message
content. A message binding describes how the abstract content is mapped into a concrete
format. However, in some cases, the abstract definition may match the concrete
representation very closely or exactly for one or more bindings, so those binding(s)
will supply little or no mapping information. However, another binding of the same
message definition may require extensive mapping information. For this reason, it is not
until the binding is inspected that one can determine "how abstract" the
message really is.
A port type is a named set of abstract operations and the abstract messages involved.
<wsdl:definitions .... >
<wsdl:portType name="nmtoken">
<wsdl:operation name="nmtoken" .... /> *
</wsdl:portType>
</wsdl:definitions>
The port type name attribute provides a unique name among all port types defined
within in the enclosing WSDL document.
An operation is named via the name attribute.
WSDL has four transmission primitives that an endpoint can support:
- One-way. The endpoint receives a message.
- Request-response. The endpoint receives a message,
and sends a correlated message.
- Solicit-response. The endpoint sends a message, and
receives a correlated message.
- Notification. The endpoint sends a message.
WSDL refers to these primitives as operations. Although request/response or
solicit/response can be modeled abstractly using two one-way messages, it is useful to
model these as primitive operation types because:
- They are very common.
- The sequence can be correlated without having to introduce
more complex flow information.
- Some endpoints can only receive messages if they are the
result of a synchronous request response.
- A simple flow can algorithmically be derived from these
primitives at the point when flow definition is desired.
Although request/response or solicit/response are logically correlated in the WSDL
document, a given binding describes the concrete correlation information. For example,
the request and response messages may be exchanged as part of one or two actual network
communications.
Although the base WSDL structure supports bindings for these four transmission
primitives, WSDL only defines bindings for the One-way and Request-response
primitives. It is expected that specifications that define the protocols for
Solicit-response or Notification would also include WSDL binding extensions that allow
use of these primitives.
Operations refer to the messages involved using the message attribute of type
QName. This attribute follows the rules defined by WSDL for linking (see section 2.1.2).
The grammar for a one-way operation is:
<wsdl:definitions .... > <wsdl:portType .... > *
<wsdl:operation name="nmtoken">
<wsdl:input name="nmtoken"? message="qname"/>
</wsdl:operation>
</wsdl:portType >
</wsdl:definitions>
The input element specifies the abstract message format for the one-way operation.
The grammar for a request-response operation is:
<wsdl:definitions .... >
<wsdl:portType .... > *
<wsdl:operation name="nmtoken" parameterOrder="nmtokens">
<wsdl:input name="nmtoken"? message="qname"/>
<wsdl:output name="nmtoken"? message="qname"/>
<wsdl:fault name="nmtoken" message="qname"/>*
</wsdl:operation>
</wsdl:portType >
</wsdl:definitions>
The input and output elements specify the abstract message format for the request and
response, respectively. The optional fault elements specify the abstract message format
for any error messages that may be output as the result of the operation (beyond those
specific to the protocol).
Note that a request-response operation is an abstract notion; a particular binding must
be consulted to determine how the messages are actually sent: within a single
communication (such as a HTTP request/response), or as two independent communications
(such as two HTTP requests).
The grammar for a solicit-response operation is:
<wsdl:definitions .... >
<wsdl:portType .... > *
<wsdl:operation name="nmtoken" parameterOrder="nmtokens">
<wsdl:output name="nmtoken"? message="qname"/>
<wsdl:input name="nmtoken"? message="qname"/>
<wsdl:fault name="nmtoken" message="qname"/>*
</wsdl:operation>
</wsdl:portType >
</wsdl:definitions>
The output and input elements specify the abstract message format for the solicited
request and response, respectively. The optional fault elements specify the abstract
message format for any error messages that may be output as the result of the operation
(beyond those specific to the protocol).
Note that a solicit-response operation is an abstract notion; a particular binding must
be consulted to determine how the messages are actually sent: within a single
communication (such as a HTTP request/response), or as two independent communications
(such as two HTTP requests).
The grammar for a notification operation is:
<wsdl:definitions .... >
<wsdl:portType .... > *
<wsdl:operation name="nmtoken">
<wsdl:output name="nmtoken"? message="qname"/>
</wsdl:operation>
</wsdl:portType >
</wsdl:definitions>
The output element specifies the abstract message format for the notification
operation.
The name attribute of the input and output elements provides a unique name among
all input and output elements within the enclosing port type.
In order to avoid having to name each input and output element within an operation, WSDL
provides some default values based on the operation name. If the name attribute is not
specified on a one-way or notification message, it defaults to the name of the
operation. If the name attribute is not specified on the input or output messages of a
request-response or solicit-response operation, the name defaults to the name of the
operation with "Request"/"Solicit" or "Response" appended,
respectively.
Each fault element must be named to allow a binding to specify the concrete format of the
fault message. The name of the fault element is unique within the set of faults defined
for the operation.
Operations do not specify whether they are to be used with RPC-like bindings or not.
However, when using an operation with an RPC-binding, it is useful to be able to capture
the original RPC function signature. For this reason, a request-response or
solicit-response operation MAY specify a list of parameter names via the
parameterOrder attribute (of type nmtokens). The value of the attribute is a
list of message part names separated by a single space. The value of the parameterOrder
attribute MUST follow the following rules:
- The part name order reflects the order of the parameters
in the RPC signature
- The return value part is not present in the list
- If a part name appears in both the input and output
message, it is an in/out parameter
- If a part name appears in only the input message, it is an
in parameter
- If a part name appears in only the output message, it is
an out parameter
Note that this information serves as a "hint" and may safely be ignored by
those not concerned with RPC signatures. Also, it is not required to be present, even if
the operation is to be used with an RPC-like binding.
2.5 Bindings
A binding defines message format and protocol details for operations and messages defined
by a particular portType. There may be any number of bindings for a given portType. The
grammar for a binding is as follows:
<wsdl:definitions .... >
<wsdl:binding name="nmtoken" type="qname"> *
<-- extensibility element (1) --> *
<wsdl:operation name="nmtoken"> *
<-- extensibility element (2) --> *
<wsdl:input name="nmtoken"? > ?
<-- extensibility element (3) -->
</wsdl:input>
<wsdl:output name="nmtoken"? > ?
<-- extensibility element (4) --> *
</wsdl:output>
<wsdl:fault name="nmtoken"> *
<-- extensibility element (5) --> *
</wsdl:fault>
</wsdl:operation>
</wsdl:binding>
</wsdl:definitions>
The name attribute provides a unique name among all bindings defined within in the
enclosing WSDL document.
A binding references the portType that it binds using the type attribute. This
QName value follows the linking rules defined by WSDL (see section 2.1.2).
Binding extensibility elements are used to specify the concrete grammar for the input
(3), output (4), and fault messages (5). Per-operation binding information (2) as well
as per-binding information (1) may also be specified.
An operation element within a binding specifies binding information for the operation
with the same name within the binding's portType. Since operation names are not required
to be unique (for example, in the case of overloading of method names), the name
attribute in the operation binding element might not be enough to uniquely identify an
operation. In that case, the correct operation should be identified by providing the
name attributes of the corresponding wsdl:input and wsdl:output elements.
A binding MUST specify exactly one protocol.
A binding MUST NOT specify address information.
A port defines an individual endpoint by specifying a single address for a binding.
<wsdl:definitions .... >
<wsdl:service .... > *
<wsdl:port name="nmtoken" binding="qname"> *
<-- extensibility element (1) -->
</wsdl:port>
</wsdl:service>
</wsdl:definitions>
The name attribute provides a unique name among all ports defined within in the
enclosing WSDL document.
The binding attribute (of type QName) refers to the binding using the linking
rules defined by WSDL (see Section 2.1.2).
Binding extensibility elements (1) are used to specify the address information for the
port.
A port MUST NOT specify more than one address.
A port MUST NOT specify any binding information other than address information.
A service groups a set of related ports together:
<wsdl:definitions .... >
<wsdl:service name="nmtoken"> *
<wsdl:port .... />*
</wsdl:service>
</wsdl:definitions>
The name attribute provides a unique name among all services defined within in the
enclosing WSDL document.
Ports within a service have the following relationship:
- None of the ports communicate with each other (e.g. the
output of one port is not the input of another).
- If a service has several ports that share a port type, but
employ different bindings or addresses, the ports are alternatives. Each
port provides semantically equivalent behavior (within the transport and
message format limitations imposed by each binding). This allows a
consumer of a WSDL document to choose particular port(s) to communicate with
based on some criteria (protocol, distance, etc.).
- By examining it's ports, we can determine a service's
port types. This allows a consumer of a WSDL document to determine if it
wishes to communicate to a particular service based whether or not it
supports several port types. This is useful if there is some
implied relationship between the operations of the port types, and that the
entire set of port types must be present in order to accomplish a particular
task.
3. SOAP Binding
WSDL includes a binding for SOAP 1.1 endpoints, which supports the specification of the
following protocol specific information:
- An indication that a binding is bound to the SOAP 1.1
protocol
- A way of specifying an address for a SOAP endpoint.
- The URI for the SOAPAction HTTP header for the HTTP
binding of SOAP
- A list of definitions for Headers that are transmitted as
part of the SOAP Envelope
This binding grammar it is not an exhaustive specification since the set of SOAP bindings
is evolving. Nothing precludes additional SOAP bindings to be derived from portions of
this grammar. For example:
- SOAP bindings that do not employ a URI addressing scheme
may substitute another addressing scheme by replacing the
soap:address element defined in section 3.8.
- SOAP bindings that do not require a SOAPAction omit the
soapAction attribute defined in section 3.4.
In the following example, a SubscribeToQuotes SOAP 1.1 one-way message is
sent to a StockQuote service via a SMTP binding. The request takes a ticker symbol of
type string, and includes a header defining the subscription URI.
Example 3. SOAP binding of one-way operation over SMTP using a SOAP
Header
<?xml version="1.0"?>
<definitions name="StockQuote"
targetNamespace="http://example.com/stockquote.wsdl"
xmlns:tns="http://example.com/stockquote.wsdl"
xmlns:xsd1="http://example.com/stockquote.xsd"
xmlns:soap="http://schemas.xmlsoap.org/wsdl/soap/"
xmlns="http://schemas.xmlsoap.org/wsdl/">
<message name="SubscribeToQuotes">
<part name="body" element="xsd1:SubscribeToQuotes"/>
<part name="subscribeheader" element="xsd1:SubscriptionHeader"/>
</message>
<portType name="StockQuotePortType">
<operation name="SubscribeToQuotes">
<input message="tns:SubscribeToQuotes"/>
</operation>
</portType>
<binding name="StockQuoteSoap" type="tns:StockQuotePortType">
<soap:binding style="document" transport="http://example.com/smtp"/>
<operation name="SubscribeToQuotes">
<input message="tns:SubscribeToQuotes">
<soap:body parts="body" use="literal"/>
<soap:header message="tns:SubscribeToQuotes" part="subscribeheader" use="literal"/>
</input>
</operation>
</binding>
<service name="StockQuoteService">
<port name="StockQuotePort" binding="tns:StockQuoteSoap">
<soap:address location="mailto:subscribe@example.com"/>
</port>
</service>
<types>
<schema targetNamespace="http://example.com/stockquote.xsd"
xmlns="http://www.w3.org/2000/10/XMLSchema">
<element name="SubscribeToQuotes">
<complexType>
<all>
<element name="tickerSymbol" type="string"/>
</all>
</complexType>
</element>
<element name="SubscriptionHeader" type="uriReference"/>
</schema>
</types>
</definitions>
This example describes that a GetTradePrice SOAP 1.1 request may be sent
to a StockQuote service via the SOAP 1.1 HTTP binding. The request takes a ticker symbol
of type string, a time of type timeInstant, and returns the price as a float in the SOAP
response.
Example 4. SOAP binding of request-response RPC operation over HTTP
<?xml version="1.0"?>
<definitions name="StockQuote"
targetNamespace="http://example.com/stockquote.wsdl"
xmlns:tns="http://example.com/stockquote.wsdl"
xmlns:xsd="http://www.w3.org/2000/10/XMLSchema"
xmlns:xsd1="http://example.com/stockquote.xsd"
xmlns:soap="http://schemas.xmlsoap.org/wsdl/soap/"
xmlns="http://schemas.xmlsoap.org/wsdl/">
<message name="GetTradePriceInput">
<part name="tickerSymbol" element="xsd:string"/>
<part name="time" element="xsd:timeInstant"/>
</message>
<message name="GetTradePriceOutput">
<part name="result" type="xsd:float"/>
</message>
<portType name="StockQuotePortType">
<operation name="GetTradePrice">
<input message="tns:GetTradePriceInput"/>
<output message="tns:GetTradePriceOutput"/>
</operation>
</portType>
<binding name="StockQuoteSoapBinding" type="tns:StockQuotePortType">
<soap:binding style="rpc" transport="http://schemas.xmlsoap.org/soap/http"/>
<operation name="GetTradePrice">
<soap:operation soapAction="http://example.com/GetTradePrice"/>
<input>
<soap:body use="encoded" namespace="http://example.com/stockquote"
encodingStyle="http://schemas.xmlsoap.org/soap/encoding/"/>
</input>
<output>
<soap:body use="encoded" namespace="http://example.com/stockquote"
encodingStyle="http://schemas.xmlsoap.org/soap/encoding/"/>
</output>
</operation>>
</binding>
<service name="StockQuoteService">
<documentation>My first service</documentation>
<port name="StockQuotePort" binding="tns:StockQuoteBinding">
<soap:address location="http://example.com/stockquote"/>
</port>
</service>
</definitions>
This example describes that a GetTradePrices SOAP 1.1 request may be sent
to a StockQuote service via the SOAP 1.1 HTTP binding. The request takes a stock quote
symbol string, an application defined TimePeriod structure containing a start and end
time and returns an array of stock prices recorded by the service within that period of
time, as well as the frequency at which they were recorded as the SOAP response.
The RPC signature that corresponds to this service has in parameters tickerSymbol and
timePeriod followed by the output parameter frequency, and returns an array of floats.
Example 5. SOAP binding of request-response RPC operation over HTTP
<?xml version="1.0"?>
<definitions name="StockQuote"
targetNamespace="http://example.com/stockquote.wsdl"
xmlns:tns="http://example.com/stockquote.wsdl"
xmlns:xsd="http://www.w3.org/2000/10/XMLSchema"
xmlns:xsd1="http://example.com/stockquote/schema"
xmlns:soap="http://schemas.xmlsoap.org/wsdl/soap/"
xmlns:soapenc="http://schemas.xmlsoap.org/soap/encoding/"
xmlns="http://schemas.xmlsoap.org/wsdl/">
<types>
<schema targetNamespace="http://example.com/stockquote/schema"
xmlns="http://www.w3.org/2000/10/XMLSchema">
<complexType name="TimePeriod">
<all>
<element name="startTime" type="xsd:timeInstant"/>
<element name="endTime" type="xsd:timeInstant"/>
</all>
</complexType>
<complexType name="ArrayOfFloat">
<complexContent>
<restriction base="soapenc:Array">
<attribute ref="soapenc:arrayType" wsdl:arrayType="xsd:float[]"/>
</restriction>
</complexContent>
</complexType>
</schema>
</types>
<message name="GetTradePricesInput">
<part name="tickerSymbol" element="xsd:string"/>
<part name="timePeriod" element="xsd1:TimePeriod"/>
</message>
<message name="GetTradePricesOutput">
<part name="result" type="xsd1:ArrayOfFloat"/>
<part name="frequency" type="xsd:float"/>
</message>
<portType name="StockQuotePortType">
<operation name="GetLastTradePrice" parameterOrder="tickerSymbol timePeriod frequency">
<input message="tns:GetTradePricesInput"/>
<output message="tns:GetTradePricesOutput"/>
</operation>
</portType>
<binding name="StockQuoteSoapBinding" type="tns:StockQuotePortType">
<soap:binding style="rpc" transport="http://schemas.xmlsoap.org/soap/http"/>
<operation name="GetTradePrices">
<soap:operation soapAction="http://example.com/GetTradePrices"/>
<input>
<soap:body use="encoded" namespace="http://example.com/stockquote"
encodingStyle="http://schemas.xmlsoap.org/soap/encoding/"/>
</input>
<output>
<soap:body use="encoded" namespace="http://example.com/stockquote"
encodingStyle="http://schemas.xmlsoap.org/soap/encoding/"/>
</output>
</operation>>
</binding>
<service name="StockQuoteService">
<documentation>My first service</documentation>
<port name="StockQuotePort" binding="tns:StockQuoteBinding">
<soap:address location="http://example.com/stockquote"/>
</port>
</service>
</definitions>
The SOAP Binding extends WSDL with the following extension elements:
<definitions .... >
<binding .... >
<soap:binding style="rpc|document" transport="uri">
<operation .... >
<soap:operation soapAction="uri"? style="rpc|document"?>?
<input>
<soap:body parts="nmtokens"? use="literal|encoded"
encodingStyle="uri-list"? namespace="uri"?>
<soap:header message="qname" part="nmtoken" use="literal|encoded"
encodingStyle="uri-list"? namespace="uri"?>*
<soap:headerfault message="qname" part="nmtoken" use="literal|encoded"
encodingStyle="uri-list"? namespace="uri"?/>*
<soap:header>
</input>
<output>
<soap:body parts="nmtokens"? use="literal|encoded"
encodingStyle="uri-list"? namespace="uri"?>
<soap:header message="qname" part="nmtoken" use="literal|encoded"
encodingStyle="uri-list"? namespace="uri"?>*
<soap:headerfault message="qname" part="nmtoken" use="literal|encoded"
encodingStyle="uri-list"? namespace="uri"?/>*
<soap:header>
</output>
<fault>*
<soap:fault name="nmtoken" use="literal|encoded"
encodingStyle="uri-list"? namespace="uri"?>
</fault>
</operation>
</binding>
<port .... >
<soap:address location="uri"/>
</port>
</definitions>
Each extension element of the SOAP binding is covered in subsequent sections.
The purpose of the SOAP binding element is to signify that the binding is bound to the
SOAP protocol format: Envelope, Header and Body. This element makes no claims as to the
encoding or format of the message (e.g. that it necessarily follows section 5 of the
SOAP 1.1 specification).
The soap:binding element MUST be present when using the SOAP binding.
<definitions .... >
<binding .... >
<soap:binding transport="uri"? style="rpc|document"?>
</binding>
</definitions>
The value of the style attribute is the default for the style attribute for each
contained operation. If the style attribute is omitted, it is assumed to be
"document". See section 3.4 for more
information on the semantics of style.
The value of the required transport attribute indicates which transport of SOAP
this binding corresponds to. The URI value http://schemas.xmlsoap.org/soap/http
corresponds to the HTTP binding in the SOAP specification. Other URIs may be used here
to indicate other transports (such as SMTP, FTP, etc.).
3.4 soap:operation
The soap:operation element provides information for the operation as a whole.
<definitions .... >
<binding .... >
<operation .... >
<soap:operation soapAction="uri"? style="rpc|document"?>?
</operation>
</binding>
</definitions>
The style attribute indicates whether the operation is RPC-oriented (messages
containing parameters and return values) or document-oriented (message containing
document(s)). This information may be used to select an appropriate programming model.
The value of this attribute also affects the way in which the Body of the SOAP message
is constructed, as explained in Section 3.5 below. If the
attribute is not specified, it defaults to the value specified in the soap:binding
element. If the soap:binding element does not specify a style, it is assumed to be
"document".
The soapAction attribute specifies the value of the SOAPAction header for this
operation. This URI value should be used directly as the value for the SOAPAction
header; no attempt should be made to make a relative URI value absolute when making the
request. For the HTTP protocol binding of SOAP, this is value required (it has no
default value). For other SOAP protocol bindings, it MUST NOT be specified, and the
soap:operation element MAY be omitted.
3.5 soap:body
The soap:body element specifies how the message parts appear inside the SOAP Body
element.
The parts of a message may either be abstract type definitions, or concrete schema
definitions. If abstract definitions, the types are serialized according to some set of
rules defined by an encoding style. Each encoding style is identified using a list of
URIs, as in the SOAP specification. Since some encoding styles such as the SOAP
Encoding (http://schemas.xmlsoap.org/soap/encoding/) allow variation in the message
format for a given set of abstract types, it is up to the reader of the message to
understand all the format variations: "reader makes right". To avoid having to
support all variations, a message may be defined concretely and then indicate it's
original encoding style (if any) as a hint. In this case, the writer of the message must
conform exactly to the specified schema: "writer makes right".
The soap:body binding element provides information on how to assemble the different
message parts inside the Body element of the SOAP message. The soap:body element is used
in both RPC-oriented and document-oriented messages, but the style of the enclosing
operation has important effects on how the Body section is structured:
- If the operation style is rpc each part is a parameter or a return value and appears
inside a wrapper element within the body (following Section 7.1 of the SOAP
specification). The wrapper element is named identically to the operation name and
its namespace is the value of the namespace attribute. Each message part
(parameter) appears under the wrapper, represented by an accessor named identically
to the corresponding parameter of the call. Parts are arranged in the same order as
the parameters of the call.
- If the operation style is document there are no additional wrappers, and the message
parts appear directly under the SOAP Body element.
The same mechanisms are used to define the content of the Body and parameter accessor
elements.
<definitions .... >
<binding .... >
<operation .... >
<input>
<soap:body parts="nmtokens"? use="literal|encoded"?
encodingStyle="uri-list"? namespace="uri"?>
</input>
<output>
<soap:body parts="nmtokens"? use="literal|encoded"?
encodingStyle="uri-list"? namespace="uri"?>
</output>
</operation>
</binding>
</definitions>
The optional parts attribute of type nmtokens indicates which parts appear
somewhere within the SOAP Body portion of the message (other parts of a message may
appear in other portions of the message such as when SOAP is used in conjunction with
the multipart/related MIME binding). If the parts attribute is omitted, then all parts
defined by the message are assumed to be included in the SOAP Body portion.
The required use attribute indicates whether the message parts are encoded using
some encoding rules, or whether the parts define the concrete schema of the message.
If use is encoded, then each message part references an abstract type using the
type attribute. These abstract types are used to produce a concrete message
by applying an encoding specified by the encodingStyle attribute. The part
names, types and value of the namespace attribute are all
inputs to the encoding, although the namespace attribute only applies to content not
explicitly defined by the abstract types. If the referenced encoding style allows
variations in it's format (such as the SOAP encoding does), then all variations MUST be
supported ("reader makes right").
If use is literal, then each part references a concrete schema definition using
either the element or type attribute. In the first case, the element
referenced by the part will appear directly under the Body element (for document style
bindings) or under an accessor element named after the message part (in rpc style). In
the second, the type referenced by the part becomes the schema type of the enclosing
element (Body for document style or part accessor element for rpc style). For an example
that illustrates defining the contents of a composite Body using a type, see section 2.3.1. The value of the encodingStyle
attribute MAY be used when the use is literal to indicate that the concrete format was
derived using a particular encoding (such as the SOAP encoding), but that only the
specified variation is supported ("writer makes right").
The value of the encodingStyle attribute is a list of URIs, each separated by a
single space. The URI's represent encodings used within the message, in order from most
restrictive to least restrictive (exactly like the encodingStyle attribute defined in
the SOAP specification).
The soap:fault element specifies the contents of the contents of the SOAP Fault Details
element. It is patterned after the soap:body element (see section
3.5).
<definitions .... >
<binding .... >
<operation .... >
<fault>*
<soap:fault name="nmtoken" use="literal|encoded"
encodingStyle="uri-list"? namespace="uri"?>
</fault>
</operation>
</binding>
</definitions>
The name attribute relates the soap:fault to the wsdl:fault defined for the
operation.
The fault message MUST have a single part. The use, encodingStyle and
namespace attributes are all used in the same way as with soap:body (see section 3.5), only style="document" is assumed
since faults do not contain parameters.
The soap:header and soap:headerfault elements allows header to be defined that are
transmitted inside the Header element of the SOAP Envelope. It is patterned after the
soap:body element (see section 3.5).
It is not necessary to exhaustively list all headers that appear in the SOAP Envelope
using soap:header. For example, extensions (see section
2.1.3) to WSDL may imply specific headers should be added to the actual payload and
it is not required to list those headers here.
<definitions .... >
<binding .... >
<operation .... >
<input>
<soap:header message="qname" part="nmtoken" use="literal|encoded"
encodingStyle="uri-list"? namespace="uri"?>*
<soap:headerfault message="qname" part="nmtoken" use="literal|encoded"
encodingStyle="uri-list"? namespace="uri"?/>*
<soap:header>
</input>
<output>
<soap:header message="qname" part="nmtoken" use="literal|encoded"
encodingStyle="uri-list"? namespace="uri"?>*
<soap:headerfault message="qname" part="nmtoken" use="literal|encoded"
encodingStyle="uri-list"? namespace="uri"?/>*
<soap:header>
</output>
</operation>
</binding>
</definitions>
The use, encodingStyle and namespace attributes are all used in the
same way as with soap:body (see section 3.5), only
style="document" is assumed since headers do not contain parameters.
Together, the message attribute (of type QName) and the part attribute (of
type nmtoken) reference the message part that defines the header type. The schema
referenced by the part MAY include definitions for the soap:actor and
soap:mustUnderstand attributes if use="literal", but MUST NOT if
use="encoded". The referenced message need not be the same as the message
that defines the SOAP Body.
The optional headerfault elements which appear inside soap:header and have the
same syntax as soap:header) allows specification of the header type(s) that are used to
transmit error information pertaining to the header defined by the soap:header. The
SOAP specification states that errors pertaining to headers must be returned in
headers, and this mechanism allows specification of the format of such headers.
3.8 soap:address
The SOAP address binding is used to give a port an address (a URI). A port using the
SOAP binding MUST specify exactly one address. The URI scheme specified for the
address must correspond to the transport specified by the soap:binding.
<definitions .... >
<port .... >
<binding .... >
<soap:address location="uri"/>
</binding>
</port>
</definitions>
4. HTTP GET & POST Binding
WSDL includes a binding for HTTP 1.1's GET and POST verbs in order to describe the
interaction between a Web Browser and a web site. This allows applications other than
Web Browsers to interact with the site. The following protocol specific information may
be specified:
- An indication that a binding uses HTTP GET or POST
- An address for the port
- A relative address for each operation (relative to the
base address defined by the port)
The following example shows three ports that are bound differently for a given port type.
If the values being passed are part1=1, part2=2, part3=3, the request format would be as
follows for each port:
port1: GET, URL="http://example.com/o1/A1B2/3"
port2: GET, URL="http://example.com/o1?p1=1&p2=2&p3=3
port3: POST, URL="http://example.com/o1", PAYLOAD="p1=1&p2=2&p3=3"
For each port, the response is either a GIF or a JPEG image.
Example 6. GET and FORM POST returning GIF or JPG
<definitions .... >
<message name="m1">
<part name="part1" type="xsd:string"/>
<part name="part2" type="xsd:int"/>
<part name="part3" type="xsd:string"/>
</message>
<message name="m2">
<part name="image" type="xsd:binary"/>
</message>
<portType name="pt1">
<operation name="o1">
<input message="tns:m1"/>
<output message="tns:m2"/>
</operation>
</portType>
<service name="service1">
<port name="port1" binding="tns:b1">
<http:address location="http://example.com/"/>
</port>
<port name="port2" binding="tns:b2">
<http:address location="http://example.com/"/>
</port>
<port name="port3" binding="tns:b3">
<http:address location="http://example.com/"/>
</port>
</service>
<binding name="b1" type="pt1">
<http:binding verb="GET"/>
<operation name="o1">
<http:operation location="o1/A(part1)B(part2)/(part3)"/>
<input>
<http:urlReplacement/>
</input>
<output>
<mime:content type="image/gif"/>
<mime:content type="image/jpeg"/>
</output>
</operation>
</binding>
<binding name="b2" type="pt1">
<http:binding verb="GET"/>
<operation name="o1">
<http:operation location="o1"/>
<input>
<http:urlEncoded/>
</input>
<output>
<mime:content type="image/gif"/>
<mime:content type="image/jpeg"/>
</output>
</operation>
</binding>
<binding name="b3" type="pt1">
<http:binding verb="POST"/>
<operation name="o1">
<http:operation location="o1"/>
<input>
<mime:content type="application/x-www-form-urlencoded"/>
</input>
<output>
<mime:content type="image/gif"/>
<mime:content type="image/jpeg"/>
</output>
</operation>
</binding>
</definitions>
The HTTP GET/POST Binding extends WSDL with the following extension elements:
<definitions .... >
<binding .... >
<http:binding verb="nmtoken"/>
<operation .... >
<http:operation location="uri"/>
<input .... >
<-- mime elements -->
</input>
<output .... >
<-- mime elements -->
</output>
</operation>
</binding>
<port .... >
<http:address location="uri"/>
</port>
</definitions>
These elements are covered in the subsequent sections.
4.3 http:address
The location attribute specifies the base URI for the port. The value of the
attribute is combined with the values of the location attribute of the http:operation
binding element. See section 4.5 for more details.
The http:binding element indicates that this binding uses the HTTP protocol.
<definitions .... >
<binding .... >
<http:binding verb="nmtoken"/>
</binding>
</definitions>
The value of the required verb attribute indicates the HTTP verb. Common values
are GET or POST, but others may be used. Note that HTTP verbs are case sensitive.
The location attribute specifies a relative URI for the operation. This URI is
combined with the URI specified in the http:address element to form the full URI for the
HTTP request. The URI value MUST be a relative URI.
<definitions .... >
<binding .... >
<operation .... >
<http:operation location="uri"/>
</operation>
</binding>
</definitions>
The urlEncoded element indicates that all the message parts are encoded into the HTTP
request URI using the standard URI-encoding rules (name1=value&name2=value...). The
names of the parameters correspond to the names of the message parts. Each value
contributed by the part is encoded using a name=value pair. This may be used with GET
to specify URL encoding, or with POST to specify a FORM-POST. For GET, the
"?" character is automatically appended as necessary.
<http:urlEncoded/>
For more information on the rules for URI-encoding parameters, see [5], [6], and [7].
The http:urlReplacement element indicates that all the message parts are encoded
into the HTTP request URI using a replacement algorithm:
- The relative URI value of http:operation is searched for a
set of search patterns.
- The search occurs before the value of the http:operation
is combined with the value of the location attribute from
http:address.
- There is one search pattern for each message part. The
search pattern string is the name of the message part surrounded with
parenthesis "(" and ")".
- For each match, the value of the corresponding message
part is substituted for the match at the location of the match.
- Matches are performed before any values are replaced
(replaced values do not trigger additional matches).
Message parts MUST NOT have repeating values.
<http:urlReplacement/>
5. MIME Binding
WSDL includes a way to bind abstract types to concrete messages in some MIME format.
Bindings for the following MIME types are defined:
- multipart/related
- text/xml
- application/x-www-form-urlencoded (the format used to
submit a form in HTML)
- Others (by specifying the MIME type string)
The set of defined MIME types is both large and evolving, so it is not a goal for WSDL to
exhaustively define XML grammar for each MIME type. Nothing precludes additional
grammar to be added to define additional MIME types as necessary. If a MIME type string
is sufficient to describe the content, the mime element defined below can be used.
Example 7. Using multipart/related with SOAP
This example describes that a GetCompanyInfo SOAP 1.1 request may be sent to a StockQuote
service via the SOAP 1.1 HTTP binding. The request takes a ticker symbol of type string.
The response contains multiple parts encoded in the MIME format multipart/related: a
SOAP Envelope containing the current stock price as a float, zero or more marketing
literature documents in HTML format, and an optional company logo in either GIF or JPEG
format.
<definitions .... >
<types>
<schema .... >
<element name="GetCompanyInfo">
<complexType>
<all>
<element name="tickerSymbol " type="string"/>
</all>
</complexType>
</element>
<element name="GetCompanyInfoResult">
<complexType>
<all>
<element name="result" type="float"/>
</all>
</complexType>
</element>
<complexType name="ArrayOfBinary">
<complexContent>
<restriction base="soapenc:Array">
<attribute ref="soapenc:arrayType" wsdl:arrayType="xsd:binary[]"/>
</restriction>
<complexContent>
</complexType>
</schema>
</types>
<message name="m1">
<part name="body" element="tns:GetCompanyInfo"/>
</message>
<message name="m2">
<part name="body" element="tns:GetCompanyInfoResult"/>
<part name="docs" type="xsd:string"/>
<part name="logo" type="tns:ArrayOfBinary"/>
</message>
<portType name="pt1">
<operation name="GetCompanyInfo">
<input message="m1"/>
<output message="m2"/>
</operation>
</portType>
<binding name="b1" type="tns:pt1">
<operation name="GetCompanyInfo">
<soap:operation soapAction="http://example.com/GetCompanyInfo"/>
<input>
<soap:body use="literal"/>
</input>
<output>
<mime:multipartRelated>
<mime:part>
<soap:body parts="body" use="literal"/>
</mime:part>
<mime:part>
<mime:content part="docs" type="text/html"/>
</mime:part>
<mime:part>
<mime:content part="logo" type="image/gif"/>
<mime:content part="logo" type="image/jpeg"/>
</mime:part>
</mime:multipartRelated>
</output>
</operation>
</binding>
<service name="CompanyInfoService">
<port name="CompanyInfoPort"binding="tns:b1">
<soap:address location="http://example.com/companyinfo"/>
</port>
</service>
</definitions>
The MIME Binding extends WSDL with the following extension elements:
<mime:content part="nmtoken"? type="string"?/>
<mime:multipartRelated>
<mime:part> *
<-- mime element -->
</mime:part>
</mime:multipartRelated>
<mime:mimeXml part="nmtoken"?/>
They are used at the following locations in WSDL:
<definitions .... >
<binding .... >
<operation .... >
<input .... >
<-- mime elements -->
</input>
<output .... >
<-- mime elements -->
</output>
</operation>
</binding>
</definitions>
MIME elements appear under input and output to specify the MIME format. If multiple
appear, they are considered to be alternatives.
To avoid having to define a new element for every MIME format, the mime:content
element may be used if there is no additional information to convey about the format
other than its MIME type string.
<mime:content part="nmtoken"? type="string"?/>
The part attribute is used to specify the name of the message part. If the message
has a single part, then the part attribute is optional. The type attribute
contains the MIME type string. A type value has two portions, separated by a slash (/),
either of which may be a wildcard (*). Not specifying the type attribute indicates that
all MIME types are acceptable.
If the return format is XML, but the schema is not known ahead of time, the generic mime
element can be used indicating text/xml:
<mime:content type="text/xml"/>
A wildcard (*) can be used to specify a family of mime types, for example all text types.
<mime:content type="text/*"/>
The following two examples both specify all mime types:
<mime:content type="*/*"/>
<mime:content/>
The multipart/related MIME type aggregates an arbitrary set of MIME formatted parts into
one message using the MIME type "multipart/related". The
mime:multipartRelated element describes the concrete format of such a
message:
<mime:multipartRelated>
<mime:part> *
<-- mime element -->
</mime:part>
</mime:multipartRelated>
The mime:part element describes each part of a multipart/related message. MIME
elements appear within mime:part to specify the concrete MIME type for the part.
If more than one MIME element appears inside a mime:part, they are alternatives.
When using the MIME binding with SOAP requests, it is legal to use the soap:body element
as a MIME element. It indicates the content type is "text/xml", and there is
an enclosing SOAP Envelope.
To specify XML payloads that are not SOAP compliant (do not have a SOAP Envelope), but do
have a particular schema, the mime:mimeXml element may be used to specify that
concrete schema. The part attribute refers to a message part defining the
concrete schema of the root XML element. The part attribute MAY be omitted if the
message has only a single part. The part references a concrete schema using the
element attribute for simple parts or type attribute for composite
parts (see section 2.3.1).
<mime:mimeXml part="nmtoken"?/>
6. References
[2] S. Bradner, "Key words for use in RFCs to Indicate Requirement
Levels", RFC 2119, Harvard
University, March 1997
[4] T. Berners-Lee, R. Fielding, L. Masinter, "Uniform Resource
Identifiers (URI): Generic Syntax", RFC 2396, MIT/LCS, U.C.
Irvine, Xerox Corporation, August 1998.
[5] http://www.w3.org/TR/html401/interact/forms.html - submit-format
[6] http://www.w3.org/TR/html401/appendix/notes.html - ampersands-in-uris
[7] http://www.w3.org/TR/html401/interact/forms.html - h-17.13.4
[8] Simple Object Access Protocol (SOAP) 1.1 "http://www.w3.org/TR/2000/NOTE-SOAP-20000508/"
[10] W3C Working Draft "XML Schema Part 1: Structures".
This is work in progress.
[11] W3C Working Draft "XML Schema Part 2: Datatypes".
This is work in progress.
This section does not directly contribute to the specification, but
provide background that may be useful when implementing the specification.
It is a common misperception to equate the targetNamespace of an XML
schema or the value of the xmlns attribute in XML instances with the location of
the corresponding schema. Since namespaces are in fact URIs, and URIs may be locations,
and you may be able to retrieve a schema from that location, it does not mean that is
the only schema that is associated with that namespace. There can be multiple schemas
associated with a particular namespace, and it is up to a processor of XML to determine
which one to use in a particular processing context. The WSDL specification provides the
processing context here via the <import> mechanism, which is based on the
XML schemas grammar for the similar concept.
Throughout this document you see fully qualified URIs used in WSDL and
XSD documents. The use of a fully qualified URI is simply to illustrate the referencing
concepts. The use of relative URIs is completely allowed and is warranted in many cases.
For information on processing relative URIs, see http://www.normos.org/ietf/rfc/rfc2396.txt.
When working with WSDL, it is sometimes desirable to make up a URI for
an entity, but not make the URI globally unique for all time and have it
"mean" that version of the entity (schema, WSDL document, etc.). There is a
particular URI base reserved for use for this type of behavior. The base URI
"http://tempuri.org/" can be used to construct a URI without any unique
association to an entity. For example, two people or programs could choose to
simultaneously use the URI "http://tempuri.org/myschema" for two completely
different schemas, and as long as the scope of the use of the URIs does not intersect,
then they are considered unique enough. This has the further benefit that the entity
referred to by the URI can be versioned without having to generate a new URI, as long as
it makes sense within the processing context. It is not recommended that
"http://tempuri.org/" be used as a base for stable, fixed entities.
SOAP Message Embedded in HTTP Request
POST /StockQuote HTTP/1.1
Host: www.stockquoteserver.com
Content-Type: text/xml; charset="utf-8"
Content-Length: nnnn
SOAPAction: "Some-URI"
<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/">
<soapenv:Body>
<m:GetLastTradePrice xmlns:m="Some-URI">
<m:tickerSymbol>DIS</m:tickerSymbol>
</m:GetLastTradePrice>
</soapenv:Body>
</soapenv:Envelope>
SOAP Message Embedded in HTTP Response
HTTP/1.1 200 OK
Content-Type: text/xml; charset="utf-8"
Content-Length: nnnn
<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/">
<soapenv:Body>
<m:GetLastTradePriceResponse xmlns:m="Some-URI">
<m:price>34.5</m:price>
</m:GetLastTradePriceResponse>
</soapenv:Body>
</soapenv:Envelope>
Extensibility elements can appear at the following locations in a WSDL document:
| Location | Meaning | Possible usage | | definitions | The extensibility element applies to the WSDL document as a
whole. | · Introduce additional information or definitions to
a WSDL document as a whole. | | definitions/types | The extensibility element is a type system. | · Specify the format of the message in a type system
other than XSD. | | definitions/service | The extensibility element applies to the service. | · Introduce additional information or definitions
for the service. | | definitions/service/port | The extensibility element applies to the port. | · Specify an address for the port. | | definitions/binding | The extensibility element applies to the binding as a whole. | · Provide protocol specific information that applies
to all the operations in the port type being bound. | | definitions/binding/operation | The extensibility element applies to the operation as a whole. | · Provide protocol specific information that applies
to both the input message and the output message. | | definitions/binding/operation/input | The extensibility element applies to the input message for the
operation. | · Provide details on how abstract message parts map
into the concrete protocol and data formats of the binding. ·
Provide additional protocol specific information for the input
message.
| | definitions/binding/operation/output | The extensibility element applies to the output message of the
operation. | · Provide details on how abstract message parts map
into the concrete protocol and data formats of the binding. ·
Provide additional protocol specific information for the output
message.
| | definitions/binding/operation/fault | The extensibility element applies to a fault message of the
operation. | · Provide details on how abstract message parts map
into the concrete protocol and data formats of the binding. ·
Provide additional protocol specific information for the fault
message.
|
<schema xmlns="http://www.w3.org/2000/10/XMLSchema"
xmlns:wsdl="http://schemas.xmlsoap.org/wsdl/"
targetNamespace="http://schemas.xmlsoap.org/wsdl/"
elementFormDefault="qualified">
<element name="documentation">
<complexType mixed="true">
<choice minOccurs="0" maxOccurs="unbounded">
<any minOccurs="0" maxOccurs="unbounded"/>
</choice>
<anyAttribute/>
</complexType>
</element>
<complexType name="documented" abstract="true">
<sequence>
<element ref="wsdl:documentation" minOccurs="0"/>
</sequence>
</complexType>
<complexType name="openAtts" abstract="true">
<annotation>
<documentation>
This type is extended by component types
to allow attributes from other namespaces to be added.
</documentation>
</annotation>
<sequence>
<element ref="wsdl:documentation" minOccurs="0"/>
</sequence>
<anyAttribute namespace="##other"/>
</complexType>
<element name="definitions" type="wsdl:definitionsType">
<key name="message">
<selector xpath="message"/>
<field xpath="@name"/>
</key>
<key name="portType">
<selector xpath="portType"/>
<field xpath="@name"/>
</key>
<key name="binding">
<selector xpath="binding"/>
<field xpath="@name"/>
</key>
<key name="service">
<selector xpath="service"/>
<field xpath="@name"/>
</key>
<key name="import">
<selector xpath="import"/>
<field xpath="@namespace"/>
</key>
<key name="port">
<selector xpath="service/port"/>
<field xpath="@name"/>
</key>
</element>
<complexType name="definitionsType">
<complexContent>
<extension base="wsdl:documented">
<sequence>
<element ref="wsdl:import" minOccurs="0" maxOccurs="unbounded"/>
<element ref="wsdl:types" minOccurs="0"/>
<element ref="wsdl:message" minOccurs="0" maxOccurs="unbounded"/>
<element ref="wsdl:portType" minOccurs="0" maxOccurs="unbounded"/>
<element ref="wsdl:binding" minOccurs="0" maxOccurs="unbounded"/>
<element ref="wsdl:service" minOccurs="0" maxOccurs="unbounded"/>
<any namespace="##other" minOccurs="0" maxOccurs="unbounded">
<annotation>
<documentation>to support extensibility elements </documentation>
</annotation>
</any>
</sequence>
<attribute name="targetNamespace" type="uriReference" use="optional"/>
<attribute name="name" type="NMTOKEN" use="optional"/>
</extension>
</complexContent>
</complexType>
<element name="import" type="wsdl:importType"/>
<complexType name="importType">
<complexContent>
<extension base="wsdl:documented">
<attribute name="namespace" type="uriR | 
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