Web Services Description Language (WSDL) Version 2.0: RDF Mapping

1. Introduction

Web Services Description Language is defined in XML, because XML is the standard format for exchange of structured information. The use of XML brings better interoperability to WSDL generators and parsers, and the use of XML Schema makes the structure of WSDL well constrained, yet extensible. On the other hand, XML vocabularies in general don't have clear composition rules, so combining for example the WSDL description of a Web service, the service's policies and other information (presumably expressed in XML) can be done in many significantly different ways (e.g. extending WSDL, extending the policy language, creating a special XML container for all the information etc.), and little interoperability can be expected when such combined documents are used.

For example, a policy can be combined with WSDL by adding the policy elements in WSDL service element. Equally, a WSDL description can be combined with a policy by adding the WSDL description as part of the policy. While the results should be similar (WSDL with policy information), they are in fact very different for the processing software, and a policy in WSDL cannot easily be used by software that doesn't know WSDL.

In contrast, the Semantic web requires knowledge from many different sources to be easily combined so that unexpected data connections can be used. For this purpose there is the Resource Description Framework (RDF), whose graph structure together with the use of URIs for identifying nodes makes it very easy for different documents to be brought together. If a WSDL document describes a Web service, a policy document attaches constraints to the service and a general description specifies the author of the service, all this information can be merged and the resulting document will contain all the three kinds of information associated with the single service.

The main objective of this specification is to present a standard RDF ([RDF]) and OWL ([OWL]) vocabulary equivalent to WSDL 2, so that WSDL 2 documents can be transformed into RDF and merged with other Semantic Web data.

Note: the readers of this document are expected to have understanding of the WSDL language and the WSDL component model; this document is not a standalone specification of the WSDL ontology, independent of WSDL specification. Further, the readers are expected to have good knowledge of RDF and at least basic knowledge of OWL.

1.1 Organization of this specification

This remainder of this specification is split into two sections and two appendices:

• Section 2 describes the ontology for representing WSDL information,
• Section 4 details the differences in modeling between the component model of WSDL and the ontology presented in this document,
• Appendix A contains the full listing of the WSDL ontology,
• Appendix B contains formal mapping tables defining the transformation from a WSDL component model to RDF data.

2. WSDL Ontology

This section describes the OWL ontology for WSDL, comparing it to the WSDL component model defined in [WSDL 2.0 Core Language]. While the text in this section may imply how the components might be mapped to their RDF representation, such implications are not intended to be normative, as this section aims to be a verbose explanation of the mapping. For the formal normative mappings, see Appendix B.

This section may also briefly touch on some differences between the OWL ontology and the component model, but for the full account and rationales of these differences see section 4.

The ontological equivalents for the core WSDL components defined in [WSDL 2.0 Core Language] are described in section 2.1. All these components are extensible, so section 2.2 describes how extensions are mapped to RDF. The following sections, from 2.3 to 2.7, describe the ontological equivalents for the various adjuncts specified in [WSDL 2.0 Adjuncts].

2.1 Core WSDL Components

All the main components of WSDL are represented as classes in the WSDL ontology: Description, Interface, Binding and Service, as described in the following subsections. This means that every interface, binding and service described by WSDL will be mapped to a single instance in the RDF representation, linked from the instance mapped from the top-level Description component.

All the components in WSDL can contain documentation. Such documentation consists of human-readable text and machine-processible elements and attributes, but it isn't modeled in more detail in WSDL 2. Therefore in the RDF mapping we represent documentation as XML literals, which should consist of the wsdl:documentation element and all its children. The literal is attached to the appropriate component in the RDF representation using the property documentation.

Ednote: documentation is not a property of components, so we have to change the above paragraph to take this directly from WSDL XML files.

2.1.1 Description class

The top-level WSDL component — description — is mapped to a single instance of the class Description, which uses the properties interface, binding and service to point to its contents, i.e. all the interfaces, bindings and services. Note that since we don't model element declarations and type definitions further than just the QNames, we also don't reference them from the Description instance. This also means that while all WSDL component models implicitly contain all XML Schema simple type definitions, the RDF mapping does not show them.

Note that a mapping of a single WSDL document (together with any imports or includes) will always result in a single instance of the Description class. However, there can be multiple individuals of the class Description in a knowledge base that contains the information from multiple WSDL documents. The core WSDL specification does not consider the case of combining multiple independent WSDL documents and it doesn't mandate that independent documents describe consistently components with the same name. This is, however, an assumption when combining multiple WSDL documents in the RDF representation. See more on this point in section 4.2.

2.1.2 Interface classes

All WSDL interfaces are represented in RDF as instances of the Interface class. WSDL interfaces can extend other interfaces, which is indicated by the property extensionOf. Interfaces may have operations and faults, represented as instances of InterfaceOperation and InterfaceFault classes and each pointed to with the properties interfaceOperation and interfaceFault, respectively.

There are a number of properties applicable to InterfaceOperation instances:

• messageExchangePattern property points to an instance of the class MessageExchangePattern and thus indicates the message exchange pattern (MEP) used by this operation; there can be only one MEP on one operation
• operationStyle property points to an instance of the class OperationStyle and indicates that the operation adheres to the given style; there can be multiple operation styles on a single operation
• interfaceMessageReference and interfaceFaultReference properties point to instances of InterfaceMessageReference and InterfaceFaultReference classes respectively, which are described later.

Interface faults, in turn, only contain a single pointer to an element declaration, represented by the property elementDeclaration and pointing to a QName instance.

Interface message references and interface fault references can indicate their direction — input message references and input fault references all belong to the class InputMessage and output message references and output fault references all belong to the class OutputMessage. Further, both message references and fault references indicate the appropriate message labels (instances of MessageLabel, representing particular messages in the operation's MEP) using the property messageLabel. (In section 2.3 we describe how message exchange patterns are modeled in our RDF mapping.)

Furthermore, interface message references point to element declarations using the property elementDeclaration and they specify their message content model with the property messageContentModel, indicating one of the four possible instances of the class MessageContentModel. And finally interface fault references refer to their interface faults directly using the property interfaceFault.

2.1.3 Binding classes

WSDL bindings are represented in RDF as instances of the class Binding. To indicate a particular interface for which binding information is specified with this WSDL binding, the particular Interface instance is pointed to using the property interface. Binding types (for example SOAP binding or HTTP binding, as specified in [WSDL 2.0 Adjuncts]) are themselves classes in RDF, so a binding type is indicated by belonging to the appropriate class (using the property rdf:type).

As the structure of bindings follows the structure of interfaces, we represent binding operations and faults using the classes BindingOperation and BindingFault respectively. The parent binding points to them using the similarly named properties bindingOperation and bindingFault. Binding operations further contain message and fault references, represented as instances of the classes BindingMessageReference and BindingFaultReference, and pointed to by the properties bindingMessageReference and bindingFaultReference.

Within this structure, each component points to the appropriate component from the interface structure, i.e. binding operations point to interface operations, binding faults respectively point to interface faults and binding message and fault references point to interface message and fault references. To provide these pointers, we reuse the same properties that are used within the interface structure, i.e. interfaceOperation, interfaceFault, interfaceMessageReference and interfaceFaultReference.

Finally, each component is supposed to contain extensions that provide the actual binding information. For the description of handling such extensions see section 2.2 and for the specific bindings included in WSDL 2 specification, see sections 2.6 and 2.7.

2.1.4 Service classes

WSDL services are represented in RDF as instances of the class Service. Each instance must point to a single interface; for this purpose we reuse the property interface. Also, each service has one or more endpoints, to which it points using the property endpoint.

Endpoints are represented as instances of the class Endpoint, with two notable properties: mandatory single binding points to the binding used by this endpoint, and optional single address points to the network resource which actually offers the service.

2.2 Handling Features, Properties and Generic Extensions

In order to enable evolution and reusability of the language, WSDL 2 allows extensions on all components. In fact, there are multiple types of extensibility in WSDL 2: extension points, abstract features and properties, and generic XML-based extensions.

Extension points are those places in WSDL where a number of options is defined by the WSDL 2 specification, but the list is open. For example, interface operations follow message exchange patterns (MEPs), and while WSDL 2 provides a list of eight MEPs, new ones can be specified by WSDL 2 users. Similarly, WSDL 2 specifies two bindings (SOAP and HTTP), but more bindings are expected to be specified in the future, either by the WS-Description Working Group or by any interested third parties. Often, extension points use URIs to refer to the various options, but often the extensions introduce data that needs to be modeled in the RDF representation of WSDL 2, in which case it is the responsibility of the extension designers to describe their mappings to RDF.

Features and properties represent abstract pieces of functionality and their run-time parameters. Mostly, features and properties simply use URIs to identify their semantics, and this easily translates into RDF, as described below in section 2.2.1.

Apart from the envisioned extensibility points and the abstract functionality extensibility using features, WSDL 2 allows the XML WSDL documents to contain any "foreign" elements and attributes, so that unexpected extensions, even ones that change the core WSDL semantics, can also be realized. Mapping such extensions to RDF is described in section 2.2.2.

2.2.1 Features and properties

Every feature component is mapped to RDF as an instance of the class Feature. This instance is identified by the feature's IRI, i.e. the value of the {ref} property of the feature component.

Features can be required or optional. In RDF, this is indicated by the property that points from the feature's parent component to the feature — it is either the requiresFeature or the offersFeature property.

Property components in WSDL 2 serve to specify or constrain the value that a property can have at run time. As one of the few naming differences between the RDF representation and the WSDL 2 component model, the property components are represented as instances of the class PropertyValue, pointed to from the property's parent component using the propertyValue RDF property.

Every PropertyValue instance points to the actual property whose value it specifies, using the RDF property named property. PropertyValue instances also either specify the actual value of the property (using the RDF property propertyActualValue) or they constrain the possible values of the property using a type definition identified by its QName (referenced from the PropertyValue instance by the RDF property propertyValueType).

2.2.2 Generic extensions

The actual meaning of general extensions is, by definition, unknown to the WSDL specification, and it is equally unknown to the RDF mapping. Therefore every extension should specify how it is mapped to RDF. For example, the SOAP and HTTP bindings in WSDL 2 add many properties to the core binding components and this document defines how these particular properties are expressed in RDF. The mapping of extensions to RDF therefore depends on the understanding of those extensions. This section describes how unknown extensions are handled when mapping a WSDL document into RDF.

In WSDL 2, extensions can be marked as mandatory (or required). Such extensions may alter the semantics of the extended components in ways that invalidate the existing semantics. Since the RDF representation of WSDL intends to represent the semantics of the WSDL data, components with required extensions must be mapped to RDF according to the rules of the extension, not according to the rules specified in this document. If a processor that does the mapping of a WSDL document to RDF does not understand a particular mandatory extension, it must not map the component that contains that extension into any generic RDF representation, in other words the component will not be present in the resulting RDF data. This is to avoid confusing processors that don't understand a mandatory extension — RDF encourages the principle of ignoring the unknown parts of an RDF graph (partial understanding) and there is no agreed mechanism of marking some parts as mandatory, therefore if we decided to map the known WSDL according to our rules and add the mandatory unknown extensions in the graph, they could be ignored by some RDF processors, violating the mandatoriness.

Finally unknown optional extensions (not mandatory) can be represented in the RDF representation using the properties extensionElement and extensionAttribute. Extension elements are represented as XML literals containing the whole extension XML elements (and should also include all the in-scope namespaces and the XML base); extension attributes are represented as instances of the class ExtensionAttribute, which in turn have a name (property attributeName pointing to a QName) and a value (property rdf:value pointing to a literal containing the attribute value).

Such representation of unknown optional extensions is not intended to be used by processors that understand those extensions; instead such processors should reinterpret the XML literals and map them into the appropriate RDF extensions of the rest of the RDF representation.

2.3 Message Exchange Patterns

WSDL 2 defines an extensible set of message exchange patterns (MEPs). There are 8 predefined MEPs, each following one of the three predefined fault propagation rules. Every WSDL MEP defines a set of message labels by which message references in operations can position themselves within the pattern.

In the RDF representation of WSDL, message exchange patterns are represented as instances of the class MessageExchangePattern. The three predefined fault propagation rules are disjoint subclasses of that class, named NoFaults, FaultReplacesMessage and MessageTriggersFault.

All MEPs are identified by IRIs, and the RDF ontology for WSDL only puts the MEPs in the correct classes; for example http://www.w3.org/2006/01/wsdl/in-only is an instance of the class NoFaults. The message labels, however, are plain string names, and the RDF ontology for WSDL gives each of them an IRI formed by the MEP IRI, the hash sign '#' and the actual message label, and these IRIs are referenced from the MEPs with the property definesMessageLabel. Any newly created MEPs should also provide IRIs for the message labels, as the RDF mapping depends on being able to identify the message labels on interface message references.

2.4 Predefined Extensions

WSDL 2 Adjuncts contain a single predefined extension, called Operation Safety, which adds a property to interface operation components to indicate whether an interface operation is known to be safe in terms of [Web Architecture].

In the RDF representation of WSDL, we introduce the class SafeInteraction — any InterfaceOperation instance that is also a SafeInteraction is asserted to be safe.

2.5 Operation Styles

WSDL 2 predefines 3 operation styles — RPC style, IRI style and Multipart style. These styles are identified with their IRIs, which the RDF ontology makes instances of the class OperationStyle.

The RPC style additionally introduces the property {rpc signature}, which is represented in RDF using the property signature, whose value is a literal whose datatype is the signature type defined by WSDL 2. The signature property can be attached to interface operations following the RPC style to indicate the parameter order for the operation.

2.6 SOAP Binding

WSDL bindings that bind to SOAP are identified (using the property rdf:type) as instances of the class http://www.w3.org/2006/01/wsdl/soap. Every such binding must indicate the SOAP version that it uses, this is done with the property version (with a value "1.2", for example, meaning SOAP version 1.2). Every binding also must specify with the property protocol the underlying protocol that is uses.

Each SOAP binding operation must specify the SOAP message exchange pattern it uses — the appropriate URI from the SOAP specification is pointed to using the property soapMEP. The ontology also introduces the class SOAPMessageExchangePattern that contains all the SOAP MEPs.

SOAP binding operations can also specify the value of the action parameter (known as SOAP action) for the initial message, using the property action.

Binding faults in the SOAP binding can specify two properties — fault code and fault subcodes. Both fault code and subcodes are QNames, and they are pointed to using the properties faultCode and faultSubcode. The latter is repeated for each subcode that the binding fault specifies.

At any level within a SOAP binding, components can declare the use of a SOAP module. Required modules are pointed to using the property requiresSOAPModule and optional modules are pointed to using the property offersSOAPModule — both of these properties point directly from the parent component to the SOAP module, as identified by its URI (parameter {ref} of the SOAP Module component).

Message references and faults in SOAP bindings can further declare that they include specific SOAP headers. To do this, the property header can point to an instance of the class SOAPHeader, which then uses the property elementDeclaration to specify the exact element that represents the header. Instances of SOAPHeader can also belong to the class MustUnderstandSOAPHeader, which means that this SOAP header will be marked as mandatory (mustUnderstand="true") in the message.

Apart from these SOAP-binding-specific properties, the SOAP binding reuses underlying protocol properties, for example some HTTP binding properties when the underlying protocol is HTTP. The following section describes the HTTP binding properties.

2.7 HTTP Binding

WSDL bindings that bind to HTTP are identified as instances of the class http://www.w3.org/2006/01/wsdl/http. The HTTP bindings that make use of HTTP cookies are further identified as instances of the class HTTPBindingWithCookies. Every HTTP binding must specify the HTTP version in use, which is done with the property version (in a different namespace from the property version in the SOAP binding), for example HTTP/1.1 is specified with the value "1.1".

HTTP binding operations can specify a number of HTTP parameters: operation-specific location, HTTP method, input and output and fault serialization, and query parameter separator. These parameters are represented in RDF with the properties location, method, inputSerialization, outputSerialization, faultSerialization and queryParameterSeparator. The values of all these properties are literals, same as in the XML syntax of WSDL.

Message references and faults in an HTTP binding can specify the use of extra HTTP headers by pointing to a QName with the property header. Message references and fault references in HTTP binding operations can also specify the transfer coding using the property transferCoding with a literal string value, as in the XML representation. Finally, faults can further specify the HTTP status code they will be accompanies with, using the property errorCode.

HTTP bindings can also specify access authentication parameters, in particular authentication type and realm. These parameters are reflected with the properties authenticationType and authenticationRealm with string values.

3. Example WSDL document in RDF form

The following is a listing of the RDF form of the WSDL description of the initial GreatH Web Service (listed as example 2-1) from the WSDL 2.0 primer (in triple notation):

@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
@prefix wsdl: <http://www.w3.org/2006/01/wsdl> .
@prefix rwsdl: <http://www.w3.org/2005/10/wsdl-rdf#> .
@prefix owl: <http://www.w3.org/2002/07/owl#> .
@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .
    
<http://greath.example.com/2004/wsdl/resSvc#wsdl.description()>     
     a rwsdl:Description ;
     rwsdl:interface <http://greath.example.com/2004/wsdl/resSvc#wsdl.interface(reservationInterface)> ;
     rwsdl:binding <http://greath.example.com/2004/wsdl/resSvc#wsdl.binding(reservationSOAPBinding)> ;
     rwsdl:service <http://greath.example.com/2004/wsdl/resSvc#wsdl.service(reservationService)> .
<http://greath.example.com/2004/wsdl/resSvc#wsdl.interface(reservationInterface)>     
     a rwsdl:Interface ;
     rwsdl:interfaceFault <http://greath.example.com/2004/wsdl/resSvc#wsdl.interfaceFault(reservationInterface/invalidDataFault)> ;
     rwsdl:interfaceOperation <http://greath.example.com/2004/wsdl/resSvc#wsdl.interfaceOperation(reservationInterface/opCheckAvailability)> .
<http://greath.example.com/2004/wsdl/resSvc#wsdl.interfaceFault(reservationInterface/invalidDataFault)>     
     a rwsdl:InterfaceFault ;
     rwsdl:elementDeclaration _:L9C14 .
<http://greath.example.com/2004/wsdl/resSvc#wsdl.interfaceFaultReference(reservationInterface/opCheckAvailability/Out/invalidDataFault)>     
     a rwsdl:InterfaceFaultReference ;
     a rwsdl:OutputMessage; 
     rwsdl:messageLabel <>; 
     rwsdl:interfaceFault <http://greath.example.com/2004/wsdl/resSvc#wsdl.interfaceFault(reservationInterface/invalidDataFault)> .
<http://greath.example.com/2004/wsdl/resSvc#wsdl.interfaceMessageReference(reservationInterface/opCheckAvailability/In)>     
     a rwsdl:InterfaceMessageReference ;
     a rwsdl:InputMessage; 
     rwsdl:elementDeclaration _:L22C18 ;
     rwsdl:messageLabel <>; 
     rwsdl:messageContentModel rwsdl:element .
<http://greath.example.com/2004/wsdl/resSvc#wsdl.interfaceMessageReference(reservationInterface/opCheckAvailability/Out)>     
     a rwsdl:InterfaceMessageReference ;
     a rwsdl:OutputMessage; 
     rwsdl:elementDeclaration _:L32C18 ;
     rwsdl:messageLabel <>; 
     rwsdl:messageContentModel rwsdl:element .
<http://greath.example.com/2004/wsdl/resSvc#wsdl.interfaceOperation(reservationInterface/opCheckAvailability)>     
     a rwsdl:InterfaceOperation ;
     rwsdl:messageExchangePattern <http://www.w3.org/2004/03/wsdl/in-out> .
     rwsdl:interfaceMessageReference <http://greath.example.com/2004/wsdl/resSvc#wsdl.interfaceMessageReference(reservationInterface/opCheckAvailability/In)> ;
     rwsdl:interfaceMessageReference <http://greath.example.com/2004/wsdl/resSvc#wsdl.interfaceMessageReference(reservationInterface/opCheckAvailability/Out)> ;
     rwsdl:interfaceFaultReference <http://greath.example.com/2004/wsdl/resSvc#wsdl.interfaceFaultReference(reservationInterface/opCheckAvailability/Out/invalidDataFault)> ;
<http://greath.example.com/2004/wsdl/resSvc#wsdl.binding(reservationSOAPBinding)>     
     a rwsdl:Binding ;
     a <http://www.w3.org/2006/01/wsdl/soap>; 
     rwsdl:interface <http://greath.example.com/2004/wsdl/resSvc#wsdl.interface(reservationInterface)> ;
     rwsdl:bindingFault <http://greath.example.com/2004/wsdl/resSvc#wsdl.bindingFault(reservationSOAPBinding/invalidDataFault)> ;
     rwsdl:bindingOperation <http://greath.example.com/2004/wsdl/resSvc#wsdl.bindingOperation(reservationSOAPBinding/opCheckAvailability)> .
<http://greath.example.com/2004/wsdl/resSvc#wsdl.bindingFault(reservationSOAPBinding/invalidDataFault)>     
     a rwsdl:BindingFault ;
     rwsdl:interfaceFault <http://greath.example.com/2004/wsdl/resSvc#wsdl.interfaceFault(reservationInterface/invalidDataFault)> .
<http://greath.example.com/2004/wsdl/resSvc#wsdl.bindingOperation(reservationSOAPBinding/opCheckAvailability)>     
     a rwsdl:BindingOperation ;
     rwsdl:interfaceOperation <http://greath.example.com/2004/wsdl/resSvc#wsdl.interfaceOperation(reservationInterface/opCheckAvailability)> .
<http://greath.example.com/2004/wsdl/resSvc#wsdl.service(reservationService)>     
     a rwsdl:Service ;
     rwsdl:interface <http://greath.example.com/2004/wsdl/resSvc#wsdl.interface(reservationInterface)> .
     rwsdl:endpoint <http://greath.example.com/2004/wsdl/resSvc#wsdl.endpoint(reservationService/reservationEndpoint)> ;
<http://greath.example.com/2004/wsdl/resSvc#wsdl.endpoint(reservationService/reservationEndpoint)>     
     a rwsdl:Endpoint ;
     rwsdl:binding <http://greath.example.com/2004/wsdl/resSvc#wsdl.binding(reservationSOAPBinding)>; 
     rwsdl:address <http://greath.example.com/2004/reservation> .
_:L9C14     
     a rwsdl:QName .
     rwsdl:localName "invalidDataError"; 
     rwsdl:namespace "http://greath.example.com/2004/schemas/resSvc"; 
_:L22C18     
     a rwsdl:QName .
     rwsdl:localName "checkAvailability"; 
     rwsdl:namespace "http://greath.example.com/2004/schemas/resSvc"; 
_:L32C18     
     a rwsdl:QName .
     rwsdl:localName "checkAvailabilityResponse"; 
     rwsdl:namespace "http://greath.example.com/2004/schemas/resSvc"; 

4. Differences from the WSDL Component Model (Informative)

WSDL defines a component model which consists of components, component properties and sets of components. This document supplies an ontology (i.e., a set of classes, properties, datatypes, and distinguished individuals) for representing WSDL data. This ontology contains axioms which express some of the constraints the WSDL specification imposes on legal sets of WSDL components whether indirectly (via the XML Schema constraints on the infoset which canonically encodes WSDL component models) or directly (via the natural language of the WSDL specs, or the corresponding Z formalizations of that language).

RDF, RDFS, and OWL are all less (and differently) expressive than the subset of Z used to formalize the WSDL specification, and are designed for different purposes. In a nutshell, RDF, RDFS, and OWL are relatively small fragments of first order logic, whereas Z encompasses all of first order logic plus set theory. Z supports validation of component models, that is, the acceptance or rejection of component models. This includes type checking, consistency checking, and the verification of integrity constraints. The current set of Semantic Web languages focus on inference and integration of information. To take a simple example, if a Z checkable representation of an Interface component lacks a {name} component property, a Z based validator will complain that that representation is ill formed (given the WSDL specification). An OWL reasoner encountering it will, all other things being equal, conclude that there is such a property, even though the reasoner has not seen it yet. In general, Semantic Web based descriptions of Web services using the WSDL conceptual framework tend to be looser than what the WSDL specification prescribes.

This difference effectively introduces two classes of documents that use the ontology from this document:

1. RDF documents resulting from translating valid WSDL documents,
2. arbitrary RDF documents written using the WSDL ontology.

This document focuses on the mapping from valid WSDL component models, and this section in particular talks about differences between a valid component model and its RDF representation.

However, we must note that arbitrary RDF, RDFS, or OWL documents that use the WSDL ontology may describe component models that are incomplete or even illegal. For example, from the point of view of arbitrary RDF documents that use the WSDL ontology, interfaces don't need to belong to any Description. Therefore, the subsections also contain notes about arbitrary RDF documents detailing further differences that an application consuming WSDL RDF data can encounter in documents that are not the direct result of mapping a valid WSDL document into its RDF form. The last subsection (section 4.5) then describes those constraints unenforced by the WSDL, that do not fit in any other subsection above it.

4.1 Component naming

In the RDF representation, all WSDL components are identified with their respective component designators (see [WSDL 2.0 Core Language] appendix C IRI-References for WSDL 2.0 Components), which are URIs generally constructed from the name and namespace of the component and from its parent component hierarchy. The original names and namespaces are not explicitly modeled in the RDF representation, which intends to convey the semantic meaning of the WSDL component, not the WSDL serialization details.

In some situations we can see the RDF representation to be used as an exchange syntax for WSDL. While it's not an intended use, it is possible that in some systems the XML syntax will be lost or inaccessibly hidden in several layers of processing software. Such an application that only receives the RDF form of WSDL can still need to reconstruct the original component names, for example if it uses an API that identifies WSDL operations by their parent interface's QName and the operation name.

The component designators put the names of the components in the fragment identifier part of the resulting URIs. On the Web (see [Web Architecture]), the interpretation of fragment identifiers is defined by the MIME media type of the representation of the resource identified by the URI without the fragment identifier. In our particular case, we expect that the namespace URI identifies an application/wsdl+xml document so that the constructed component designator fragment identifiers can have their intended meaning. An application working with the RDF representation of WSDL can reconstruct the names of the components by reversing the process that resulted in the component designator, for example for a URI http://example.com/service#wsdl.interfaceOperation(TicketInterface/BookTicket) we could reconstruct that the name of the interface is "TicketInterface" in the namespace http://example.com/service and that the operation is named "BookTicket".

Such decomposition is only valid, though, if the URI http://example.com/service identifies a document of MIME media type application/wsdl+xml, as explained above. Checking the MIME media type of every resource identified by a URI in an RDF graph could be prohibitively slow for some applications, therefore it may be practical (albeit not entirely correct) simply to assume the correct media type and deconstruct the component names without the preceding media type check.

Note about arbitrary RDF documents: in general, it is possible to assert about any resource (identified by any kind of URI) that it is, for example, a WSDL operation, and if an application tries to deconstruct that URI according to WSDL component designator specification, it may find that the URI doesn't conform to the syntax (e.g. http://example.com/service/operation) or, by accident or malice, it does conform to the syntax but doesn't contain the correct data (e.g. http://example.com/service#wsdl.interface(TicketInterface) that is marked to be a WSDL operation, not an interface as it would seem).

4.2 Documents, imports and includes

In the XML syntax for WSDL, documents can be included and imported, allowing for modularization while keeping the ability to validate that a WSDL document (plus all the includes and imports) doesn't use any unknown components. Such modularization is lost when the WSDL files are parsed into a component model, therefore a straigtforward transformation of such a component model into RDF will result in a single RDF document.

As one exception, all references to element declarations and type definitions from XML Schema are done in the RDF representation by QName and we expect the applications processing this representation to have means of locating the appropriate descriptions for these QNames. We do not model XML Schema (or any other) type and element descriptions in this ontology.

Note about arbitrary RDF documents: RDF data can be split into any number of pieces, which can be put together by the processing application as appropriate. If a piece of WSDL/RDF description uses an unknown component (e.g. an interface described in one document may extend other interfaces, not described in this document), the application may, if necessary, attempt to locate the description of the unknown component, for example using its identifier IRI. Note that RDF does not provide a standard generic way of including external data, so any inclusion is application-specific.

Additionally, a single RDF document may also contain multiple unrelated Descriptions, that is, it may be an aggregation of many unrelated WSDL documents, and this may have unexpected results if the aggregated WSDL data contains conflicts, i.e. different definitions of components with the same name; especially when dealing with different versions of descriptions of the same entities.

4.3 Component references

In the XML representation of WSDL, components are referred to using their names, and extensibility points usually use IRIs to identify things. All these references are, from XML point of view, literals. In the RDF representation, on the other hand, most references are direct, using the particular identifier IRIs, not represented as literals. For example, most instances representing components are identified with their component designators (see [WSDL 2.0 Core Language] appendix C IRI-References for WSDL 2.0 Components) and all references point directly there — an operation within a binding points to its respective interface operation using the interface operation component designator IRI, whereas in the XML syntax the operations are correlated using the message label.

As a notable exception, references to type definitions and element declarations (usually from XML Schema) are represented as instances of our class QName, with both namespace and local part represented as literals. This might change if a standard RDF representation for XML Schema element declarations and type definitions is developed — then direct references to the URIs used in that representation would be used.

Ednote: Additionally, certain components in WSDL are only pointers, they only have a single literal property that points to an external thing. For example, the feature component only carries the URI of the feature, and the HTTP Header component only carries an element QName. While these components can contain documentation and extensions in WSDL, we chose to represent these components as direct links from the parent component to the target feature or the element QName, as the indirection seems to add very little value.

4.4 Representing properties with classes

In certain cases the RDF mapping introduces classes where the WSDL 2 component model has a property with a limited number of values. For instance, instead of having a direction property on message and fault references, with the values either "in" or "out", we introduce two classes, InputMessage and OutputMessage, and the direction of a particular message or fault reference is then indicated by belonging to either of these classes. Similarly, binding types are classes and the type of a particular binding is indicated by its belonging to that class; we predefine the two classes for the two bindings that are part of WSDL 2. Finally, the operation safety property is represented with the class SafeInteraction, and safe operations are instances of this class.

On a similar note, in the case of features, the flag that a feature is required is not modeled as a property of the feature component, required features are instead pointed to using the RDF property requiresFeature, whereas optional features are pointed to using the property offersFeature.

4.5 Other WSDL restrictions not enforced by the ontology

As already mentioned, the validation-oriented WSDL specification and especially its Z formalization capture a number of restrictions and limitations that are not expressed in the RDF ontology. None of these restrictions or limitations can be violated when a valid WSDL document is mapped into its RDF form. When the RDF data is directly manipulated, for example merged with other RDF data (for example other WSDL documents mapped into RDF), or when new data is created that uses the WSDL ontology, further significant WSDL constraints might be violated:

• In WSDL, components of different types do not overlap, e.g. an interface is always a different thing from a binding (even if they have the same name), but an arbitrary RDF document can assert that one resource is both an interface and a binding.
• In WSDL, a Description cannot directly contain interface operations or endpoints, for example; an endpoint is always in a service and interface operations are always in interfaces. The ontology does not enforce these restrictions so an arbitrary RDF file that is consistent with the ontology may describe a broken hierarchy of components.

5. References

[OWL]

OWL Web Ontology Language Reference, Mike Dean,Guus Schreiber, Editors. W3C Recommendation 10 February 2004 . Available at http://www.w3.org/TR/owl-ref/

[RDF]

Resource Description Framework (RDF): Concepts and Abstract Syntax, Graham Klyne, Jeremy J. Carroll, Editors. W3C Recommendation, 10 February 2004. Available at http://www.w3.org/TR/rdf-concepts/

[Web Architecture]

Architecture of the World Wide Web, Volume One, Ian Jacobs, Norman Walsh, Editors. W3C Recommendation, 15 December, 2004. Available at http://www.w3.org/TR/2004/REC-webarch-20041215/ .

[WSDL 2.0 Core Language]

Web Services Description Language (WSDL) Version 2.0 Part 1: Core Language, R. Chinnici, M. Gudgin, J-J. Moreau, S. Weerawarana, Editors. World Wide Web Consortium, 27 March 2006. This version of the "Web Services Description Language (WSDL) Version 2.0 Part 1: Core Language" Specification is available is available at http://www.w3.org/TR/2006/CR-wsdl20-20060327. The latest version of "Web Services Description Language (WSDL) Version 2.0 Part 1: Core Language" is available at http://www.w3.org/TR/wsdl20.

[WSDL 2.0 Adjuncts]

Web Services Description Language (WSDL) Version 2.0 Part 2: Adjuncts , R. Chinnici, H. Haas, A. Lewis, J-J. Moreau, D. Orchard, S. Weerawarana, Editors. World Wide Web Consortium, 27 March 2006. This version of the "Web Services Description Language (WSDL) Version 2.0 Part 2: Adjuncts" Specification is available at http://www.w3.org/TR/2006/CR-wsdl20-adjuncts-20060327. The latest version of "Web Services Description Language (WSDL) Version 2.0 Part 2: Adjuncts" is available at http://www.w3.org/TR/wsdl20-adjuncts.

Appendix A: The OWL Ontology Source

Note that the ontology is also available in a separate RDF file.

<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
         xmlns:owl="http://www.w3.org/2002/07/owl#"
         xmlns:rdfs="http://www.w3.org/2000/01/rdf-schema#"
         xmlns:wsdl="http://www.w3.org/2005/10/wsdl-rdf#"
         xmlns:xml="http://www.w3.org/XML/1998/namespace"
         xml:base="http://www.w3.org/2005/10/wsdl-rdf">

<!-- the following are notes on the deviations this model has from the WSDL2
component model:

direction - msg ref or fault ref instance of inputmessage or outputmessage

feature is a direct reference, property is indirect

binding types as classes (or subclasses of binding)

for us, MEPs are one individual of MessageExchangePattern and a number of
individuals of MessageLabel

fault propagation rules in MEPs are modeled as subclasses of MEP

message labels are qualified with mep name and so are different for each MEP

maybe we could model safety as general-purpose class of things safe, now it's
a class of safe operations

documentation, extensions not handled on HTTP header - maybe a
mapping using blank node and rdf:value? headers also don't use the component
designators as they go directly to the qname
-->

<!-- todo maybe rename properties to verbs and adjectives? -->

<owl:Ontology rdf:about="">
</owl:Ontology>

<owl:Class rdf:about="#Binding">
</owl:Class>

<owl:Class rdf:about="#BindingFault">
</owl:Class>

<owl:Class rdf:about="#BindingFaultReference">
</owl:Class>

<owl:Class rdf:about="#BindingMessageReference">
</owl:Class>

<owl:Class rdf:about="#BindingOperation">
  <rdfs:comment>The type of a binding is indicated with rdf:type</rdfs:comment>
</owl:Class>

<owl:Class rdf:about="#Description">
</owl:Class>

<owl:Class rdf:about="#Endpoint">
  <rdfs:subClassOf>
    <owl:Restriction>
      <owl:onProperty rdf:resource="#address"/>
      <owl:maxCardinality rdf:datatype="http://www.w3.org/2001/XMLSchema#nonNegativeInteger">1</owl:maxCardinality>
    </owl:Restriction>
  </rdfs:subClassOf>
</owl:Class>

<owl:Class rdf:about="#Feature">
</owl:Class>

<owl:Class rdf:about="#Interface">
  <rdfs:label>WDSL Interface</rdfs:label>
</owl:Class>

<owl:Class rdf:about="#InterfaceFault">
</owl:Class>

<owl:Class rdf:about="#InterfaceFaultReference">
</owl:Class>

<owl:Class rdf:about="#InterfaceMessageReference">
  <rdfs:subClassOf>
    <owl:Restriction>
      <owl:onProperty rdf:resource="#messageContentModel"/>
      <owl:cardinality rdf:datatype="http://www.w3.org/2001/XMLSchema#nonNegativeInteger">1</owl:cardinality>
    </owl:Restriction>
  </rdfs:subClassOf>
</owl:Class>

<owl:Class rdf:about="#InputMessage">
  <rdfs:comment>To be used by message references and fault references instead of direction property</rdfs:comment>
  <owl:disjointWith rdf:resource="#OutputMessage"/>
</owl:Class>

<owl:Class rdf:about="#OutputMessage">
  <rdfs:comment>To be used by message references and fault references instead of direction property</rdfs:comment>
</owl:Class>

<owl:Class rdf:about="#InterfaceOperation">
  <rdfs:subClassOf>
    <owl:Restriction>
      <owl:onProperty rdf:resource="#messageExchangePattern"/>
      <owl:cardinality rdf:datatype="http://www.w3.org/2001/XMLSchema#nonNegativeInteger">1</owl:cardinality>
    </owl:Restriction>
  </rdfs:subClassOf>
</owl:Class>

<owl:Class rdf:about="#PropertyValue">
  <rdfs:subClassOf>
    <owl:Restriction>
      <owl:onProperty rdf:resource="#propertyValue"/>
      <owl:cardinality rdf:datatype="http://www.w3.org/2001/XMLSchema#nonNegativeInteger">1</owl:cardinality>
    </owl:Restriction>
  </rdfs:subClassOf>
</owl:Class>

<owl:Class rdf:about="#Property">
</owl:Class>

<owl:Class rdf:about="#Service">
</owl:Class>

<owl:Class rdf:about="#MessageExchangePattern">
</owl:Class>

<owl:Class rdf:about="#MessageLabel">
</owl:Class>

<owl:ObjectProperty rdf:about="#definesMessageLabel">
  <rdfs:domain rdf:resource="#MessageExchangePattern"/>
  <rdfs:range  rdf:resource="#MessageLabel"/>
</owl:ObjectProperty>

<owl:ObjectProperty rdf:about="#address">
  <rdfs:domain rdf:resource="#Endpoint"/>
</owl:ObjectProperty>

<owl:ObjectProperty rdf:about="#binding">
  <rdfs:range  rdf:resource="#Binding"/>
  <rdfs:comment>To be used for pointing to a Binding, for example from Description or Endpoint</rdfs:comment>
</owl:ObjectProperty>

<owl:ObjectProperty rdf:about="#bindingFault">
  <rdfs:range  rdf:resource="#BindingFault"/>
</owl:ObjectProperty>

<owl:ObjectProperty rdf:about="#bindingOperation">
  <rdfs:range  rdf:resource="#BindingOperation"/>
</owl:ObjectProperty>

<owl:ObjectProperty rdf:about="#bindingMessageReference">
  <rdfs:range  rdf:resource="#BindingMessageReference"/>
</owl:ObjectProperty>

<owl:ObjectProperty rdf:about="#bindingFaultReference">
  <rdfs:range  rdf:resource="#BindingFaultReference"/>
</owl:ObjectProperty>

<owl:ObjectProperty rdf:about="#typeDefinition">
  <rdfs:range  rdf:resource="#QName"/>
</owl:ObjectProperty>

<owl:ObjectProperty rdf:about="#elementDeclaration">
  <rdfs:range  rdf:resource="#QName"/>
</owl:ObjectProperty>

<owl:ObjectProperty rdf:about="#endpoint">
  <rdfs:range  rdf:resource="#Endpoint"/>
</owl:ObjectProperty>

<owl:ObjectProperty rdf:about="#extensionOf">
  <rdfs:range  rdf:resource="#Interface"/>
  <rdfs:domain rdf:resource="#Interface"/>
</owl:ObjectProperty>

<owl:Class rdf:about="#QName">
  <rdfs:subClassOf>
    <owl:Restriction>
      <owl:onProperty rdf:resource="#localName"/>
      <owl:cardinality rdf:datatype="http://www.w3.org/2001/XMLSchema#nonNegativeInteger">1</owl:cardinality>
    </owl:Restriction>
  </rdfs:subClassOf>
  <rdfs:subClassOf>
    <owl:Restriction>
      <owl:onProperty rdf:resource="#namespace"/>
      <owl:cardinality rdf:datatype="http://www.w3.org/2001/XMLSchema#nonNegativeInteger">1</owl:cardinality>
    </owl:Restriction>
  </rdfs:subClassOf>
</owl:Class>

<owl:DatatypeProperty rdf:about="#localName">
  <rdfs:range  rdf:resource="http://www.w3.org/2001/XMLSchema#NCName"/>
</owl:DatatypeProperty>

<owl:DatatypeProperty rdf:about="#namespace">
  <rdfs:range  rdf:resource="http://www.w3.org/2001/XMLSchema#anyURI"/>
</owl:DatatypeProperty>

<owl:ObjectProperty rdf:about="#offersFeature">
  <rdfs:range  rdf:resource="#Feature"/>
</owl:ObjectProperty>

<owl:ObjectProperty rdf:about="#requiresFeature">
  <rdfs:range  rdf:resource="#Feature"/>
</owl:ObjectProperty>

<owl:ObjectProperty rdf:about="#interface">
  <rdfs:range  rdf:resource="#Interface"/>
</owl:ObjectProperty>

<owl:ObjectProperty rdf:about="#interfaceFault">
  <rdfs:range  rdf:resource="#InterfaceFault"/>
</owl:ObjectProperty>

<owl:ObjectProperty rdf:about="#interfaceFaultReference">
  <rdfs:range  rdf:resource="#InterfaceFaultReference"/>
</owl:ObjectProperty>

<owl:ObjectProperty rdf:about="#interfaceMessageReference">
  <rdfs:range  rdf:resource="#InterfaceMessageReference"/>
</owl:ObjectProperty>

<owl:ObjectProperty rdf:about="#operationStyle">
  <rdfs:domain rdf:resource="#InterfaceOperation"/>
  <rdfs:range  rdf:resource="#OperationStyle"/>
  <rdfs:comment>
    points to one style this operation conforms to (can be used multiple times
    to point to multiple styles)
  </rdfs:comment>
</owl:ObjectProperty>

<owl:ObjectProperty rdf:about="#interfaceOperation">
  <rdfs:range  rdf:resource="#InterfaceOperation"/>
  <rdfs:comment>
    can be used on interface to link to an operation and on a binding
    operation to link to the interface operation that is being bound
  </rdfs:comment>
</owl:ObjectProperty>

<owl:ObjectProperty rdf:about="#messageContentModel">
  <rdfs:range  rdf:resource="#MessageContentModel"/>
</owl:ObjectProperty>

<owl:Class rdf:about="#MessageContentModel">
  <owl:oneOf rdf:parseType="Collection">
      <wsdl:MessageContentModel rdf:about="#AnyContent"/>
      <wsdl:MessageContentModel rdf:about="#NoContent"/>
      <wsdl:MessageContentModel rdf:about="#ElementContent"/>
      <wsdl:MessageContentModel rdf:about="#OtherContent"/>
  </owl:oneOf>
</owl:Class>

<owl:ObjectProperty rdf:about="#messageExchangePattern">
  <rdfs:range  rdf:resource="#MessageExchangePattern"/>
</owl:ObjectProperty>

<owl:ObjectProperty rdf:about="#messageLabel">
  <rdfs:range  rdf:resource="#MessageLabel"/>
</owl:ObjectProperty>

<owl:ObjectProperty rdf:about="#propertyValue">
  <rdfs:range  rdf:resource="#PropertyValue"/>
</owl:ObjectProperty>

<owl:ObjectProperty rdf:about="#property">
  <rdfs:range  rdf:resource="#Property"/>
</owl:ObjectProperty>

<owl:DatatypeProperty rdf:about="#propertyActualValue">
  <rdfs:domain rdf:resource="#PropertyValue"/>
  <rdfs:range  rdf:resource="http://www.w3.org/1999/02/22-rdf-syntax-ns#XMLLiteral"/>
</owl:DatatypeProperty>

<owl:ObjectProperty rdf:about="#propertyValueType">
  <rdfs:domain rdf:resource="#PropertyValue"/>
  <rdfs:range  rdf:resource="#QName"/>
</owl:ObjectProperty>

<owl:ObjectProperty rdf:about="#service">
  <rdfs:range  rdf:resource="#Service"/>
</owl:ObjectProperty>

<owl:DatatypeProperty rdf:about="#documentation">
  <rdfs:range  rdf:resource="http://www.w3.org/1999/02/22-rdf-syntax-ns#XMLLiteral"/>
</owl:DatatypeProperty>

<!-- todo - can we combine extensionElement property with extensionAttribute
into an "extension" property? Problem is the first is datatype and the second
is object property - is that a real problem? -->

<owl:DatatypeProperty rdf:about="#extensionElement">
  <rdfs:range  rdf:resource="http://www.w3.org/1999/02/22-rdf-syntax-ns#XMLLiteral"/>
</owl:DatatypeProperty>

<owl:ObjectProperty rdf:about="#extensionAttribute">
  <rdfs:range  rdf:resource="#ExtensionAttribute"/>
</owl:ObjectProperty>

<owl:Class rdf:about="#ExtensionAttribute">
  <rdfs:subClassOf>
    <owl:Restriction>
      <owl:onProperty rdf:resource="#attributeName"/>
      <owl:cardinality rdf:datatype="http://www.w3.org/2001/XMLSchema#nonNegativeInteger">1</owl:cardinality>
    </owl:Restriction>
  </rdfs:subClassOf>
  <rdfs:subClassOf>
    <owl:Restriction>
      <owl:onProperty rdf:resource="http://www.w3.org/1999/02/22-rdf-syntax-ns#value"/>
      <owl:cardinality rdf:datatype="http://www.w3.org/2001/XMLSchema#nonNegativeInteger">1</owl:cardinality>
    </owl:Restriction>
  </rdfs:subClassOf>
  <rdfs:comment>
    Represents an extension attribute with a name and a value. The value
    should be a literal. This should only be used for extension attributes
    that aren't understood by the generator of the RDF model, otherwise the
    extension should define how the attribute shows in the RDF model.
  </rdfs:comment>
</owl:Class>

<owl:ObjectProperty rdf:about="#attributeName">
  <rdfs:range  rdf:resource="#QName"/>
</owl:ObjectProperty>


<!-- part 2: message exchange patterns -->

<owl:Class rdf:about="#NoFaults">
  <rdfs:subClassOf rdf:resource="#MessageExchangePattern" />
  <owl:disjointWith rdf:resource="#FaultReplacesMessage"/>
  <owl:disjointWith rdf:resource="#MessageTriggersFault"/>
</owl:Class>

<owl:Class rdf:about="#FaultReplacesMessage">
  <rdfs:subClassOf rdf:resource="#MessageExchangePattern" />
  <owl:disjointWith rdf:resource="#MessageTriggersFault"/>
</owl:Class>

<owl:Class rdf:about="#MessageTriggersFault">
  <rdfs:subClassOf rdf:resource="#MessageExchangePattern" />
</owl:Class>

<wsdl:NoFaults rdf:about="http://www.w3.org/2006/01/wsdl/in-only">
  <wsdl:definesMessageLabel>
    <wsdl:MessageLabel rdf:about="http://www.w3.org/2006/01/wsdl/in-only#In"/>
  </wsdl:definesMessageLabel>
</wsdl:NoFaults>

<wsdl:NoFaults rdf:about="http://www.w3.org/2006/01/wsdl/out-only">
  <wsdl:definesMessageLabel>
    <wsdl:MessageLabel rdf:about="http://www.w3.org/2006/01/wsdl/out-only#Out"/>
  </wsdl:definesMessageLabel>
</wsdl:NoFaults>

<wsdl:MessageTriggersFault rdf:about="http://www.w3.org/2006/01/wsdl/robust-in-only">
  <wsdl:definesMessageLabel>
    <wsdl:MessageLabel rdf:about="http://www.w3.org/2006/01/wsdl/robust-in-only#In"/>
  </wsdl:definesMessageLabel>
</wsdl:MessageTriggersFault>

<wsdl:MessageTriggersFault rdf:about="http://www.w3.org/2006/01/wsdl/in-opt-out">
  <wsdl:definesMessageLabel>
    <wsdl:MessageLabel rdf:about="http://www.w3.org/2006/01/wsdl/in-opt-out#In"/>
  </wsdl:definesMessageLabel>
  <wsdl:definesMessageLabel>
    <wsdl:MessageLabel rdf:about="http://www.w3.org/2006/01/wsdl/in-opt-out#Out"/>
  </wsdl:definesMessageLabel>
</wsdl:MessageTriggersFault>

<wsdl:MessageTriggersFault rdf:about="http://www.w3.org/2006/01/wsdl/robust-out-only">
  <wsdl:definesMessageLabel>
    <wsdl:MessageLabel rdf:about="http://www.w3.org/2006/01/wsdl/robust-out-only#Out"/>
  </wsdl:definesMessageLabel>
</wsdl:MessageTriggersFault>

<wsdl:MessageTriggersFault rdf:about="http://www.w3.org/2006/01/wsdl/out-opt-in">
  <wsdl:definesMessageLabel>
    <wsdl:MessageLabel rdf:about="http://www.w3.org/2006/01/wsdl/out-opt-in#Out"/>
  </wsdl:definesMessageLabel>
  <wsdl:definesMessageLabel>
    <wsdl:MessageLabel rdf:about="http://www.w3.org/2006/01/wsdl/out-opt-in#In"/>
  </wsdl:definesMessageLabel>
</wsdl:MessageTriggersFault>

<wsdl:FaultReplacesMessage rdf:about="http://www.w3.org/2006/01/wsdl/in-out">
  <wsdl:definesMessageLabel>
    <wsdl:MessageLabel rdf:about="http://www.w3.org/2006/01/wsdl/in-out#In"/>
  </wsdl:definesMessageLabel>
  <wsdl:definesMessageLabel>
    <wsdl:MessageLabel rdf:about="http://www.w3.org/2006/01/wsdl/in-out#Out"/>
  </wsdl:definesMessageLabel>
</wsdl:FaultReplacesMessage>

<wsdl:FaultReplacesMessage rdf:about="http://www.w3.org/2006/01/wsdl/out-in">
  <wsdl:definesMessageLabel>
    <wsdl:MessageLabel rdf:about="http://www.w3.org/2006/01/wsdl/out-in#Out"/>
  </wsdl:definesMessageLabel>
  <wsdl:definesMessageLabel>
    <wsdl:MessageLabel rdf:about="http://www.w3.org/2006/01/wsdl/out-in#In"/>
  </wsdl:definesMessageLabel>
</wsdl:FaultReplacesMessage>

<!-- part 2: safety -->

<owl:Class rdf:about="http://www.w3.org/2006/01/wsdl-extensions#SafeInteraction">
  <rdfs:subClassOf rdf:resource="#InterfaceOperation" />
  <rdfs:comment>
    Class of all operations that are asserted to be safe interactions as defined in
    Web Architecture at W3C.
  </rdfs:comment>
</owl:Class>

<!-- part 2: operation styles -->

<wsdl:OperationStyle rdf:about="http://www.w3.org/2006/01/wsdl/style/rpc">
  <rdfs:comment>RPC operation style</rdfs:comment>
</wsdl:OperationStyle>

<owl:DatatypeProperty rdf:about="http://www.w3.org/2006/01/wsdl/rpc#signature">
  <rdfs:domain rdf:resource="#InterfaceOperation"/>
  <rdfs:range  rdf:resource="http://www.w3.org/2006/01/wsdl/rpc#signatureType"/>
  <rdfs:comment>todo - can we use the above URI for the datatype of this property?</rdfs:comment>
</owl:DatatypeProperty>

<wsdl:OperationStyle rdf:about="http://www.w3.org/2006/01/wsdl/style/iri">
  <rdfs:comment>IRI operation style</rdfs:comment>
</wsdl:OperationStyle>

<wsdl:OperationStyle rdf:about="http://www.w3.org/2006/01/wsdl/style/multipart">
  <rdfs:comment>multipart operation style</rdfs:comment>
</wsdl:OperationStyle>



<!-- part 2: bindings -->

<!-- SOAP binding -->

<owl:Class rdf:about="http://www.w3.org/2006/01/wsdl/soap">
  <rdfs:comment>WSDL 2 SOAP binding</rdfs:comment>
  <rdfs:subClassOf>
    <owl:Restriction>
      <owl:onProperty rdf:resource="http://www.w3.org/2006/01/wsdl/soap#version"/>
      <owl:cardinality rdf:datatype="http://www.w3.org/2001/XMLSchema#nonNegativeInteger">1</owl:cardinality>
    </owl:Restriction>
  </rdfs:subClassOf>
  <rdfs:subClassOf>
    <owl:Restriction>
      <owl:onProperty rdf:resource="http://www.w3.org/2006/01/wsdl/soap#protocol"/>
      <owl:cardinality rdf:datatype="http://www.w3.org/2001/XMLSchema#nonNegativeInteger">1</owl:cardinality>
    </owl:Restriction>
  </rdfs:subClassOf>
</owl:Class>

<owl:DatatypeProperty rdf:about="http://www.w3.org/2006/01/wsdl/soap#version">
  <rdfs:comment>
    indicates what version of SOAP is used by the binding, usually "1.2"
    todo - using string is fairly ugly, but can we invent URIs?
  </rdfs:comment>
  <rdfs:range  rdf:resource="http://www.w3.org/2001/XMLSchema#string"/>
</owl:DatatypeProperty>

<owl:ObjectProperty rdf:about="http://www.w3.org/2006/01/wsdl/soap#protocol">
  <rdfs:comment>
    indicates the underlying protocol used by a binding
    todo - protocol class and the known instances?
  </rdfs:comment>
</owl:ObjectProperty>

<owl:ObjectProperty rdf:about="http://www.w3.org/2006/01/wsdl/soap#faultCode">
  <rdfs:comment>
    indicates the fault code of a binding fault
  </rdfs:comment>
  <rdfs:range  rdf:resource="#QName"/>
</owl:ObjectProperty>

<owl:ObjectProperty rdf:about="http://www.w3.org/2006/01/wsdl/soap#faultSubcode">
  <rdfs:comment>
    indicates a fault subcode of a binding fault; there can be multiple subcodes
    todo - the list of subcodes is ordered in SOAP 1.2
  </rdfs:comment>
  <rdfs:range  rdf:resource="#QName"/>
</owl:ObjectProperty>

<owl:ObjectProperty rdf:about="http://www.w3.org/2006/01/wsdl/soap#soapMEP">
  <rdfs:comment>
    indicates the SOAP MEP this binding operation uses
  </rdfs:comment>
  <rdfs:range rdf:resource="http://www.w3.org/2006/02/soap12/abstractions#classOfMEPs"/>
</owl:ObjectProperty>

<owl:ObjectProperty rdf:about="http://www.w3.org/2006/01/wsdl/soap#defaultSoapMEP">
  <rdfs:comment>
    indicates the default SOAP MEP this binding's operations use
  </rdfs:comment>
  <rdfs:range rdf:resource="http://www.w3.org/2006/02/soap12/abstractions#classOfMEPs"/>
</owl:ObjectProperty>

<owl:Class rdf:about="http://www.w3.org/2006/02/soap12/abstractions#classOfMEPs">
  <rdfs:comment>
    todo - the URI of this class could be SOAP-1.2-specific, not WSDL2-specific
  </rdfs:comment>
</owl:Class>

<rdf:Description rdf:about="http://www.w3.org/2003/05/soap/mep/request-response/">
  <rdf:type rdf:resource="http://www.w3.org/2006/02/soap12/abstractions#classOfMEPs"/>
</rdf:Description>

<rdf:Description rdf:about="http://www.w3.org/2003/05/soap/mep/soap-response/">
  <rdf:type rdf:resource="http://www.w3.org/2006/02/soap12/abstractions#classOfMEPs"/>
</rdf:Description>

<owl:ObjectProperty rdf:about="http://www.w3.org/2006/01/wsdl/soap#action">
  <rdfs:comment>
    indicates the SOAP action this binding operation uses
  </rdfs:comment>
</owl:ObjectProperty>

<owl:ObjectProperty rdf:about="http://www.w3.org/2006/01/wsdl/soap#offersSOAPModule">
  <rdfs:range  rdf:resource="http://www.w3.org/2006/01/wsdl/soap#SOAPModule"/>
</owl:ObjectProperty>

<owl:ObjectProperty rdf:about="http://www.w3.org/2006/01/wsdl/soap#requiresSOAPModule">
  <rdfs:range  rdf:resource="http://www.w3.org/2006/01/wsdl/soap#SOAPModule"/>
</owl:ObjectProperty>

<owl:Class rdf:about="http://www.w3.org/2006/01/wsdl/soap#SOAPModule">
  <rdfs:comment>
    a SOAP module; a WSDL 2 SOAP binding (and subcomponents) may use or
    require any number of modules
  </rdfs:comment>
</owl:Class>

<owl:ObjectProperty rdf:about="http://www.w3.org/2006/01/wsdl/soap#header">
  <rdfs:range  rdf:resource="http://www.w3.org/2006/01/wsdl/soap#SOAPHeader"/>
</owl:ObjectProperty>

<owl:Class rdf:about="http://www.w3.org/2006/01/wsdl/soap#SOAPHeader">
  <rdfs:comment>
    a SOAP header
  </rdfs:comment>
  <rdfs:subClassOf>
    <owl:Restriction>
      <owl:onProperty rdf:resource="#elementDeclaration"/>
      <owl:cardinality rdf:datatype="http://www.w3.org/2001/XMLSchema#nonNegativeInteger">1</owl:cardinality>
    </owl:Restriction>
  </rdfs:subClassOf>
</owl:Class>

<owl:Class rdf:about="http://www.w3.org/2006/01/wsdl/soap#MustUnderstandSOAPHeader">
  <rdfs:subClassOf rdf:resource="http://www.w3.org/2006/01/wsdl/soap#SOAPHeader" />
  <rdfs:comment>
    a SOAP header that must be marked as mustUnderstand by the sender
  </rdfs:comment>
</owl:Class>

<!-- HTTP binding -->

<owl:Class rdf:about="http://www.w3.org/2006/01/wsdl/http">
  <rdfs:comment>WSDL 2 HTTP binding</rdfs:comment>
</owl:Class>

<owl:DatatypeProperty rdf:about="http://www.w3.org/2006/01/wsdl/http#location">
  <rdfs:comment>
    defines the location for an operation, relative to the address of the
    service; this is the only URI-valued property modeled as datatype
    property because the URI is not meant as pointer to a resource
  </rdfs:comment>
  <rdfs:range  rdf:resource="http://www.w3.org/2001/XMLSchema#anyURI"/>
</owl:DatatypeProperty>

<owl:DatatypeProperty rdf:about="http://www.w3.org/2006/01/wsdl/http#defaultMethod">
  <rdfs:comment>
    declares the default HTTP method used by this binding's operations
  </rdfs:comment>
  <rdfs:range  rdf:resource="http://www.w3.org/2001/XMLSchema#string"/>
</owl:DatatypeProperty>

<owl:DatatypeProperty rdf:about="http://www.w3.org/2006/01/wsdl/http#method">
  <rdfs:comment>
    declares the HTTP method used by this operation
  </rdfs:comment>
  <rdfs:range  rdf:resource="http://www.w3.org/2001/XMLSchema#string"/>
</owl:DatatypeProperty>

<owl:DatatypeProperty rdf:about="http://www.w3.org/2006/01/wsdl/http#inputSerialization">
  <rdfs:comment>
    declares the media type of the input message of an operation
  </rdfs:comment>
  <rdfs:range  rdf:resource="http://www.w3.org/2001/XMLSchema#string"/>
</owl:DatatypeProperty>

<owl:DatatypeProperty rdf:about="http://www.w3.org/2006/01/wsdl/http#outputSerialization">
  <rdfs:comment>
    declares the media type of the output message of an operation
  </rdfs:comment>
  <rdfs:range  rdf:resource="http://www.w3.org/2001/XMLSchema#string"/>
</owl:DatatypeProperty>

<owl:DatatypeProperty rdf:about="http://www.w3.org/2006/01/wsdl/http#faultSerialization">
  <rdfs:comment>
    declares the media type of the fault messages of an operation
  </rdfs:comment>
  <rdfs:range  rdf:resource="http://www.w3.org/2001/XMLSchema#string"/>
</owl:DatatypeProperty>

<owl:DatatypeProperty rdf:about="http://www.w3.org/2006/01/wsdl/http#defaultQueryParameterSeparator">
  <rdfs:comment>
    declares the default character to be used as query parameter separator by this binding's operations
  </rdfs:comment>
  <rdfs:range  rdf:resource="http://www.w3.org/2001/XMLSchema#string"/>
</owl:DatatypeProperty>

<owl:DatatypeProperty rdf:about="http://www.w3.org/2006/01/wsdl/http#queryParameterSeparator">
  <rdfs:comment>
    declares the character to be used as query parameter separator by an operation
  </rdfs:comment>
  <rdfs:range  rdf:resource="http://www.w3.org/2001/XMLSchema#string"/>
</owl:DatatypeProperty>

<owl:ObjectProperty rdf:about="http://www.w3.org/2006/01/wsdl/http#header">
  <rdfs:range  rdf:resource="#QName"/>
</owl:ObjectProperty>

<owl:DatatypeProperty rdf:about="http://www.w3.org/2006/01/wsdl/http#errorCode">
  <rdfs:comment>
    declares the error status code that a fault will return
  </rdfs:comment>
  <rdfs:range  rdf:resource="http://www.w3.org/2001/XMLSchema#int"/>
</owl:DatatypeProperty>

<owl:DatatypeProperty rdf:about="http://www.w3.org/2006/01/wsdl/http#errorReason">
  <rdfs:comment>
    declares the error reason phrase that a fault will return
  </rdfs:comment>
  <rdfs:range  rdf:resource="http://www.w3.org/2001/XMLSchema#string"/>
</owl:DatatypeProperty>

<owl:DatatypeProperty rdf:about="http://www.w3.org/2006/01/wsdl/http#defaultTransferCoding">
  <rdfs:comment>
    declares the default transfer coding to be used by this binding's operation messages
  </rdfs:comment>
  <rdfs:range  rdf:resource="http://www.w3.org/2001/XMLSchema#string"/>
</owl:DatatypeProperty>

<owl:DatatypeProperty rdf:about="http://www.w3.org/2006/01/wsdl/http#transferCoding">
  <rdfs:comment>
    declares the transfer coding to be used by operation messages
  </rdfs:comment>
  <rdfs:range  rdf:resource="http://www.w3.org/2001/XMLSchema#string"/>
</owl:DatatypeProperty>

<owl:Class rdf:about="http://www.w3.org/2006/01/wsdl/http#HTTPBindingWithCookies">
  <rdfs:comment>WSDL 2 HTTP binding with cookies</rdfs:comment>
  <rdfs:subClassOf rdf:resource="http://www.w3.org/2006/01/wsdl/http"/>
</owl:Class>

<owl:DatatypeProperty rdf:about="http://www.w3.org/2006/01/wsdl/http#authenticationType">
  <rdfs:comment>
    declares the authentication type used by an endpoint, by default "none"
  </rdfs:comment>
  <rdfs:range  rdf:resource="http://www.w3.org/2001/XMLSchema#string"/>
</owl:DatatypeProperty>

<owl:DatatypeProperty rdf:about="http://www.w3.org/2006/01/wsdl/http#authenticationRealm">
  <rdfs:comment>
    declares the authentication realm used by an endpoint
  </rdfs:comment>
  <rdfs:range  rdf:resource="http://www.w3.org/2001/XMLSchema#string"/>
</owl:DatatypeProperty>





<!-- todo binding defaults are necessary for interfaceless bindings, but they
aren't currently in the component model - they are modeled here tho, in
anticipation that my LC comment gets accepted -->

</rdf:RDF>

Appendix B: mapping wsdl files to rdf

Ednote: The following tables are a preliminary version of the envisioned final mapping, which will include a proper description of what the tables mean and how they are to be interpreted.

Conventions: currentInterface corresponds to the interface being defined, while interfaces related to its via one of the XML children are denoted by one or two-letter abbreviations (e.g. io for interface operation, if for interface fault)

Table 2-1. Mapping from Description Component Properties to RDF Triples

WSDL Component	RDF Triples
description aDescription	descriptionId rdf:type wsdlont:Description
interface anInterface (for rest of interface properties see Table 2-2)	descriptionId interface interfaceId
binding aBinding (for rest of binding properties see Table 2-3)	descriptionId binding bindingId
service aService (for rest of service properties see Table 2-4)	descriptionId service serviceId

Table 2-2. Mapping from Interface Component Properties to RDF Triples

WSDL Component	RDF Triples
interface anInterface	interfaceId rdf:type wsdlont:Interface
extensionOf anotherInterface	interfaceId extensionOf anotherInterfaceId anotherInterfaceId rdf:type wsdlont:Interface
interfaceOperation io (for rest of interface operation properties see Table 2-6)	interfaceId interfaceOperation ioId
interfaceFault if	interfaceId interfaceFault ifId ifId rdf:type wsdlont:InterfaceFault

Table 2-3. Mapping from Binding Component Properties to RDF Triples

WSDL Component	RDF Triples
binding aBinding	bindingId rdf:type wsdlont:Binding
interface anInterface	bindingId interface interfaceId interfaceId rdf:type wsdlont:Interface
bindingOperation bo (for rest of binding operation properties see Table 2-10)	bindingId bindingOperation boId
bindingFault bf (for rest of binding fault properties see Table 2-9)	bindingId bindingFault bfId

Table 2-4. Mapping from Service Component Properties to RDF Triples

WSDL Component	RDF Triples
service aService	serviceId rdf:type wsdlont:Service
interface anInterface	serviceId interface interfaceId
endpoint anEndpoint (for rest of endpoint properties see Table 2-11)	serviceId endpoint endpointId

Table 2-6. Mapping from InterfaceOperation Component Properties to RDF Triples

WSDL Component	RDF Triples
interfaceOperation io	ioId rdf:type wsdlont:InterfaceOperation
interfaceMessageReference imf (for rest of interface message reference properties see Table 2-7)	ioId interfaceMessageReference imrId
interfaceFaultReference ifr (for rest of interface fault reference properties see Table 2-8)	ioId interfaceFaultReference ifrId
operationStyle os	ioId operationStyle osId osId rdf:type wsdlont:OperationStyle
messageExchangePattern mep	ioId messageExchangePattern mepId mepId rdf:type wsdlont:MessageExchangePattern

Table 2-7. Mapping from Component Properties to RDF Triples

WSDL Component	RDF Triples
interfaceMessageReference imr	imrId rdf:type wsdlont:InterfaceMessageReference
messageContentModel mcm	imrId messageContentModel mcmId mcmId rdf:type wsdlont:MessageContentModel

Table 2-8. Mapping from Component Properties to RDF Triples

WSDL Component	RDF Triples
interfaceFaultReference ifr	ifrId rdf:type wsdlont:InterfaceFaultReference
interfaceFault if	ifr interfaceFault ifId ifId rdf:type wsdlont:InterfaceFault

Table 2-9. Mapping from BindingFault Component Properties to RDF Triples

WSDL Component	RDF Triples
bindingFault bf	bfId rdf:type wsdlont:BindingFault

Table 2-10. Mapping from BindingOperation Component Properties to RDF Triples

WSDL Component	RDF Triples
bindingOperation bo	boId rdf:type wsdlont:BindingOperation
bindingMessageReference bmr	boId bindingMessageReference bmrId bmrId rdf:type wsdlont:BindingMessageReference
bindingFaultReference bfr	boId bindingFaultReference bfrId bfrId rdf:type wsdlont:BindingFaultReference

Table 2-11. Mapping from Component Properties to RDF Triples

WSDL Component	RDF Triples
endpoint anEndpoint	endpointId rdf:type wsdlont:Endpoint
binding aBinding	endpointId binding bindingId
address anAddress	endpointId address aURI