Web Services Description in RDF

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 great interoperability in for 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 result should be similar (WSDL combined with policy is the same as policy combined with WSDL, right?), 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 about 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 assigned to the single service.

The main objective of this specification is to present a standard RDF vocabulary equivalent to WSDL 2, so that all 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 specification is split into five main parts — three sections and two appendices:

• Section 2 describes the ontology for representing WSDL information,
• Section 3 details the differences in modeling between the component model of WSDL and the ontology presented in this document,
• Section 4 presents various uses for the RDF representation of WSDL,
• 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 WSDL2 Core. 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; 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 rationalization of these differences see section 3.

The ontological equivalents for the core WSDL components defined in WSDL2 Core are described in section 2.1. All these components are extensible, so section 2.2 describes how features, properties and extensions are mapped to RDF. The following sections, from 2.3 to 2.7, describe the ontological equivalents for the various adjuncts specified in WSDL2 Adjuncts.

2.1 Core WSDL Components

All the main components of WSDL are represented as classes in the WSDL ontology: 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. There is no class for the top-level Description component, as it serves only as the mandatory XML root element for documents containing WSDL descriptions.

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.

2.1.1 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. Interface fault references, on the other hand, refer to their interface faults directly using the property interfaceFault.

2.1.2 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 WSDL2 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.

2.1.3 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 unknown required extensions must be mapped to RDF according to the rules of the extension, not according to the rules specified in this document. 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 their 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/2005/08/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 URIs 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

todo

2.7 HTTP Binding

todo

3. Differences from the WSDL Component Model

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 langauges 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, albeit unknown.

RDF, RDFS, or OWL documents using the ontology presented in this document may describe component models which are incomplete, or illegal, or contain extentions (new components, etc.). They may contain multiple unrelated Descriptions, that is, they may be aggregations of many unrelated WSDL documents. In general, Semantic Web based descriptions of Web services using the WSDL conceptual framework tend to be looser than what the WSDL spec prescribes.

Apart from this difference stemming from the fundamental intentional differences between strict specification (supporting validation) and Semantic Web modeling (supporting inference), there are a number of other differences between the ontological model presented in this document and the component model of WSDL. These differences are detailed in the following subsections.

3.1 Component naming

In the RD representation, all WSDL components are identified with their respective component designators (see todo ref), which are URIs generally constructed from the namespace and name 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 [todo ref webarch], 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. Such applications, though, must be aware that in the RDF representation 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).

3.2 Documents, imports and includes

The RDF representation of WSDL does not have the notion of a top-level Description component containing a logical group of WSDL components. Instead, when represented in RDF, components can be viewed as free-floating pieces of description, which should be easily combinable with other information about related resources. Strictly speaking, just like interfaces don't need to belong to any Description, interface operations don't actually need to belong to any interface in the RDF representation.

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. In RDF, data can generally be split into any number of pieces, which can be put together by the application as appropriate. If a piece of WSDL description uses an unknown component (an interface described in one document may extend other interface, not described in this document), the application may, if necessary, attempt to locate the description of the unknown component using its identifier IRI.

The same reasoning applies to the schema documents included and imported in WSDL. All references to element declarations and type definitions are done by QName in the RDF representation 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.

3.3 Component references

In the XML representation of WSDL, components are refered 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 todo ref) and all references point directly there. The one notable exception are references to type definitions and element declarations (usually from XML Schema) which 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 WSDL2, 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.

3.4 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.

appendix A: the owl ontology source

<?xml version="1.0"?>
<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/@@@@/wsdl#"
         xmlns:xml="http://www.w3.org/XML/1998/namespace"
         xml:base="http://www.w3.org/@@@@/wsdl">

<!-- todo modularize into many more namespaces -->

<!-- todo add all easily modelable constraints (or remove them altogether)
BJP: We coudl have two documents...one pure RDFS with just the subclass and
subproperty trees adn then an owl document with the remaining axioms that
imports the first document
JK: good idea, can be postponed for a moment but I like it
-->

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

<!-- BJP: It would be better to have an xml:base. I converted allthe identifiers to the equivalent relative uris.

BTW. The new pretty printer in swoop does a much better job. I'll add the standard entities tomorrow...I'm beat right now :) -->

<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="#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 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">
      <owl:Thing rdf:about="#AnyContent"/>
      <owl:Thing rdf:about="#NoContent"/>
      <owl:Thing rdf:about="#ElementContent"/>
      <owl:Thing 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>

<!-- todo - the naming of this and preceding may be confusing -->
<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:DatatypeProperty>

<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/2005/08/wsdl/in-only">
  <wsdl:definesMessageLabel>
    <wsdl:MessageLabel rdf:about="http://www.w3.org/2005/08/wsdl/in-only#In"/>
  </wsdl:definesMessageLabel>
</wsdl:NoFaults>

<wsdl:NoFaults rdf:about="http://www.w3.org/2005/08/wsdl/out-only">
  <wsdl:definesMessageLabel>
    <wsdl:MessageLabel rdf:about="http://www.w3.org/2005/08/wsdl/out-only#Out"/>
  </wsdl:definesMessageLabel>
</wsdl:NoFaults>

<wsdl:MessageTriggersFault rdf:about="http://www.w3.org/2005/08/wsdl/robust-in-only">
  <wsdl:definesMessageLabel>
    <wsdl:MessageLabel rdf:about="http://www.w3.org/2005/08/wsdl/robust-in-only#In"/>
  </wsdl:definesMessageLabel>
</wsdl:MessageTriggersFault>

<wsdl:MessageTriggersFault rdf:about="http://www.w3.org/2005/08/wsdl/in-opt-out">
  <wsdl:definesMessageLabel>
    <wsdl:MessageLabel rdf:about="http://www.w3.org/2005/08/wsdl/in-opt-out#In"/>
  </wsdl:definesMessageLabel>
  <wsdl:definesMessageLabel>
    <wsdl:MessageLabel rdf:about="http://www.w3.org/2005/08/wsdl/in-opt-out#Out"/>
  </wsdl:definesMessageLabel>
</wsdl:MessageTriggersFault>

<wsdl:MessageTriggersFault rdf:about="http://www.w3.org/2005/08/wsdl/robust-out-only">
  <wsdl:definesMessageLabel>
    <wsdl:MessageLabel rdf:about="http://www.w3.org/2005/08/wsdl/robust-out-only#Out"/>
  </wsdl:definesMessageLabel>
</wsdl:MessageTriggersFault>

<wsdl:MessageTriggersFault rdf:about="http://www.w3.org/2005/08/wsdl/out-opt-in">
  <wsdl:definesMessageLabel>
    <wsdl:MessageLabel rdf:about="http://www.w3.org/2005/08/wsdl/out-opt-in#Out"/>
  </wsdl:definesMessageLabel>
  <wsdl:definesMessageLabel>
    <wsdl:MessageLabel rdf:about="http://www.w3.org/2005/08/wsdl/out-opt-in#In"/>
  </wsdl:definesMessageLabel>
</wsdl:MessageTriggersFault>

<wsdl:FaultReplacesMessage rdf:about="http://www.w3.org/2005/08/wsdl/in-out">
  <wsdl:definesMessageLabel>
    <wsdl:MessageLabel rdf:about="http://www.w3.org/2005/08/wsdl/in-out#In"/>
  </wsdl:definesMessageLabel>
  <wsdl:definesMessageLabel>
    <wsdl:MessageLabel rdf:about="http://www.w3.org/2005/08/wsdl/in-out#Out"/>
  </wsdl:definesMessageLabel>
</wsdl:FaultReplacesMessage>

<wsdl:FaultReplacesMessage rdf:about="http://www.w3.org/2005/08/wsdl/out-in">
  <wsdl:definesMessageLabel>
    <wsdl:MessageLabel rdf:about="http://www.w3.org/2005/08/wsdl/out-in#Out"/>
  </wsdl:definesMessageLabel>
  <wsdl:definesMessageLabel>
    <wsdl:MessageLabel rdf:about="http://www.w3.org/2005/08/wsdl/out-in#In"/>
  </wsdl:definesMessageLabel>
</wsdl:FaultReplacesMessage>

<!-- part 2: safety -->

<owl:Class rdf:about="http://www.w3.org/2005/08/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/2005/08/wsdl/style/rpc">
  <rdfs:comment>RPC operation style</rdfs:comment>
</wsdl:OperationStyle>

<owl:DatatypeProperty rdf:about="http://www.w3.org/2005/08/wsdl/rpc#signature">
  <rdfs:domain rdf:resource="#InterfaceOperation"/>
  <rdfs:range  rdf:resource="http://www.w3.org/2005/08/wsdl/rpc#signatureType"/>
  <rdfs:comment>todo - can I use the above URI for the datatype of this property?</rdfs:comment>
</owl:DatatypeProperty>

<wsdl:OperationStyle rdf:about="http://www.w3.org/2005/08/wsdl/style/iri">
  <rdfs:comment>IRI operation style</rdfs:comment>
</wsdl:OperationStyle>

<wsdl:OperationStyle rdf:about="http://www.w3.org/2005/08/wsdl/style/multipart">
  <rdfs:comment>multipart operation style</rdfs:comment>
</wsdl:OperationStyle>



<!-- part 2: bindings - todo split out -->

<!-- SOAP binding -->

<owl:Class rdf:about="http://www.w3.org/2005/08/wsdl/soap">
  <rdfs:comment>WSDL 2 SOAP binding</rdfs:comment>
  <rdfs:subClassOf>
    <owl:Restriction>
      <owl:onProperty rdf:resource="http://www.w3.org/2005/08/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/2005/08/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/2005/08/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/2005/08/wsdl/soap#protocol">
  <rdfs:comment>
    indicates the underlying protocol used by a binding
  </rdfs:comment>
</owl:ObjectProperty>

<owl:ObjectProperty rdf:about="http://www.w3.org/2005/08/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/2005/08/wsdl/soap#faultSubcode">
  <rdfs:comment>
    indicates a fault subcode of a binding fault; there can be multiple subcodes
  </rdfs:comment>
  <rdfs:range  rdf:resource="#QName"/>
</owl:ObjectProperty>

<owl:ObjectProperty rdf:about="http://www.w3.org/2005/08/wsdl/soap#soapMEP">
  <rdfs:comment>
    indicates the SOAP MEP this binding operation uses
  </rdfs:comment>
  <rdfs:range  rdf:resource="#SOAPMessageExchangePattern"/>
</owl:ObjectProperty>

<owl:ObjectProperty rdf:about="http://www.w3.org/2005/08/wsdl/soap#defaultSoapMEP">
  <rdfs:comment>
    indicates the default SOAP MEP this binding's operations use
  </rdfs:comment>
  <rdfs:range  rdf:resource="#SOAPMessageExchangePattern"/>
</owl:ObjectProperty>

<owl:Class rdf:about="#SOAPMessageExchangePattern">
  <rdfs:comment>
    todo - the URI of this class could be SOAP-1.2-specific, not WSDL2-specific
  </rdfs:comment>
</owl:Class>

<wsdl:SOAPMessageExchangePattern 
    rdf:about="http://www.w3.org/2003/05/soap/mep/request-response/"/>

<wsdl:SOAPMessageExchangePattern 
    rdf:about="http://www.w3.org/2003/05/soap/mep/soap-response/"/>

<owl:ObjectProperty rdf:about="http://www.w3.org/2005/08/wsdl/soap#action">
  <rdfs:comment>
    indicates the SOAP action this binding operation uses
    todo - change "operation" to "message reference" when that change happens to the spec
  </rdfs:comment>
</owl:ObjectProperty>

<owl:ObjectProperty rdf:about="http://www.w3.org/2005/08/wsdl/soap#offersSOAPModule">
  <rdfs:range  rdf:resource="http://www.w3.org/2005/08/wsdl/soap#SOAPModule"/>
</owl:ObjectProperty>

<owl:ObjectProperty rdf:about="http://www.w3.org/2005/08/wsdl/soap#requiresSOAPModule">
  <rdfs:range  rdf:resource="http://www.w3.org/2005/08/wsdl/soap#SOAPModule"/>
</owl:ObjectProperty>

<owl:Class rdf:about="http://www.w3.org/2005/08/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/2005/08/wsdl/soap#header">
  <rdfs:range  rdf:resource="http://www.w3.org/2005/08/wsdl/soap#SOAPHeader"/>
</owl:ObjectProperty>

<owl:Class rdf:about="http://www.w3.org/2005/08/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/2005/08/wsdl/soap#MustUnderstandSOAPHeader">
  <rdfs:subClassOf rdf:resource="http://www.w3.org/2005/08/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/2005/08/wsdl/http">
  <rdfs:comment>WSDL 2 HTTP binding</rdfs:comment>
  <rdfs:subClassOf>
    <owl:Restriction>
      <owl:onProperty rdf:resource="http://www.w3.org/2005/08/wsdl/http#version"/>
      <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/2005/08/wsdl/http#version">
  <rdfs:comment>
    indicates what version of SOAP is used by the binding, usually "1.1"
    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:DatatypeProperty rdf:about="http://www.w3.org/2005/08/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/2005/08/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/2005/08/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/2005/08/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/2005/08/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/2005/08/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/2005/08/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/2005/08/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/2005/08/wsdl/http#header">
  <rdfs:range  rdf:resource="#QName"/>
</owl:ObjectProperty>

<owl:DatatypeProperty rdf:about="http://www.w3.org/2005/08/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/2005/08/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/2005/08/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/2005/08/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/2005/08/wsdl/http#WithCookies">
  <rdfs:comment>WSDL 2 HTTP binding with cookies</rdfs:comment>
  <rdfs:subClassOf rdf:resource="http://www.w3.org/2005/08/wsdl/http"/>
</owl:Class>

<owl:DatatypeProperty rdf:about="http://www.w3.org/2005/08/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/2005/08/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

todo: mapping there, not really back, certainly not roundtrip

todo