Web InterFace Language

Object Classes

The WIFL object classes may have associations with other object classes and attributes whose types are attribute classes. The object classes and their associations and attributes are shown in the UML class diagrams below.

Object Classes
Class	Summary
Example	An example of an HTTP message exchange.
ExampleHeader	An example HTTP header.
ExampleRequest	An example HTTP request.
ExampleResponse	An example HTTP response.
Parameter	A request or response parameter.
Parameterized	The abstract base class of all classes that may have parameters.
Representation	A resource's representation.
Request	A request to a resource.
Resource	A collection of a resource's sub-resources, requests and their common parameters.
Response	A response to a request.

Example

An example of an HTTP message exchange.

Associations
Name	Class	Multiplicity	Description
exampleRequest	ExampleRequest	*	An example request.
exampleResponse	ExampleResponse	*	An example response.
seeAlso	Thing	*	The URI of a related resource.

ExampleHeader

An example HTTP header.

Attributes
Name	Class	Arity	Description
name	fieldName	1	The header's name.
value	fieldValue	1	The header's value.

ExampleRequest

An example HTTP request.

Associations
Name	Class	Multiplicity	Description
exampleHeader	ExampleHeader	*	An example header.

Attributes
Name	Class	Arity	Description
body	string	1	The request's content, if any.
method	verb	1	The request's HTTP verb (e.g. GET, POST, PUT, DELETE).
uri	anyURI	1	The request's URI.

ExampleResponse

An example HTTP response.

Associations
Name	Class	Multiplicity	Description
exampleHeader	ExampleHeader	*	An example header.

Attributes
Name	Class	Arity	Description
body	string	1	The response's content, if any. If the response's Content-Length is missing, the body is "" (the empty string).
status	statusCode	1	The HTTP status code.

Parameter

A request or response parameter.

Associations
Name	Class	Multiplicity	Description
dataType	DataType	0..1	The parameters datatype. Default: xsd:string.

Attributes
Name	Class	Arity	Description
defaultValue	string	1	The parameter's default value, if any.
fixed	boolean	1	Whether the parameter's value is constant. If true, the defaultValue must contain the value. Default: false.
name	paramName	1	The parameter's name.
required	boolean	1	Whether the parameter is required. Default: false.

Parameterized

The abstract base class of all classes that may have parameters. A parameterized object contributes its associated parameters to an HTTP request. The association's name indicates where the parameter appears in the request.

Subclass: Request
Subclass: Resource

Associations
Name	Class	Multiplicity	Description
headerParam	Parameter	*	A parameter that appears in a request header.
pathParam	Parameter	*	A parameter that appears in the path of request's URI.
queryParam	Parameter	*	A parameter that appears in a request's query string.

Representation

A resource's representation. The representation is carried in the body of an HTTP request or response. The following representation instances are pre-defined:

wifl:Empty: The empty representation contains the empty string "".
wifl:JSON: The JSON representation contains a schema-less JSON string. The contentType is application/json.
wifl:XML: The XML representation contains a schema-less XML document. The contentType is application/xml.

Associations
Name	Class	Multiplicity	Description
representationType	RepresentationType	0..1	The type of the representation. Default: rdfs:Resource.

Attributes
Name	Class	Arity	Description
contentType	mediaType	1	The representation's media type. The value appears in the Content-Type header of an HTTP request or response.

Request

A request to a resource.

A request has exactly one HTTP method.

A request can support zero or more alternative representations in its body. All of a request's representations are logically equivalent. A GET request typically has an empty body, and would not have any representation associations, while a POST request would have a representation association for each supported content type. A request has a response association for each possible response.

A request's complete set of pathParams is that of its resource. A request's complete set of queryParams includes those it specifies directly and that of its resource. A request's complete set of headerParams includes those it specifies directly and that of its resource. If a request and its resource have different parameters with the same name, the request's parameter is used.

Given a Request object, generate an HTTP request by following these steps:

Set the HTTP method to the value of the Request's method attribute.
Generate the URL.
1. Create the Request's URI template by
  1. Creating an RFC 6570 URI template expression whose operator is ? and whose variable-list has a varspec for each member of the Request's complete set of queryParams. The varspec is a varname whose value is that of the queryParam's name attribute.
  2. Appending the URI template expression to the Request's Resource's complete URI path template.
2. Create a binding for each name of the Request's complete set of pathParams and fixed or non-default queryParams from the Request's complete set of queryParams to the corresponding value in the run-time environment.
3. Expand the Request's URI template according to RFC 6570 using the binding created in the previous step.
Add the request headers.
1. Create a binding for each name of the non-default headerParams from the Request's complete set of headerParams to the corresponding value in the run-time environment.
2. For each member of the binding, add an HTTP header where the header name is the variable's name and the header value is the variable's value.

If a Representation is to be submitted in the HTTP request, include the following steps:

Set the HTTP request's Content-Type header to the value of the selected Representation's contentType attribute value.
Add the entity body to the HTTP request.

Superclass: Parameterized

Associations
Name	Class	Multiplicity	Description
representation	Representation	*	A representation that may be carried by this request.
response	Response	*	A response that may be returned.

Attributes
Name	Class	Arity	Description
method	verb	1	The request's HTTP verb (e.g. GET, POST, PUT, DELETE).

Resource

A collection of a resource's sub-resources, requests and their common parameters.

A resource may support a number of different requests. A resource may specify parameters that are common to its requests.

A resource may declare itself to be a sub-resource of another resource by using the parent association. A resource may declare its type to be that of another resource with the super association.

A resource's complete URI path template is computed by appending its path value to the complete URI path template of its parent resource.

A resource's complete sets of pathParams, queryParams, and headerParams include those it specifies directly and those it inherits. A resource inherits pathParams from its parent resource, if any. A resource inherits queryParams and headerParams from its super resources, if any. If a resource specifies a parameter with the same name as one it inherits, the resource's parameter is used.

A resource's complete set of requests and responses includes those it specifies directly and the complete sets of its super resources.

Superclass: Parameterized

Associations
Name	Class	Multiplicity	Description
parent	Resource	0..1	A parent that provides a base URI path template and path parameters.
request	Request	*	A request supported by the resource.
response	Response	*	A response that may be returned for one or more requests.
super	Resource	*	Super-resources that provide requests, responses, queryParams, and headerParams.

Attributes
Name	Class	Arity	Description
path	uriTemplate	0..1	A URI template for the resource's path. The path is specified by a URI template, which conforms to RFC 6570, excluding Path-style Parameter Expansion, Form-style Parameter Expansion, and Form-style Query Continuation. The path is ignored, and may be omitted, when the resource acts as a type for other resources.

Response

A response to a request. A response has a list of possible HTTP status codes. A response can support zero or more alternative representations in its body. All of a response's representations are logically equivalent.

Associations
Name	Class	Multiplicity	Description
headerParam	Parameter	*	A parameter returned in the response header.
representation	Representation	*	A representation carried by the response.

Attributes
Name	Class	Arity	Description
status	statusCode	1..*	A list of the response's possible HTTP status codes.

Datatype Classes

Attribute classes do not have associations or attributes. Many are defined by reference to an IETF RFC or a W3C Recommendation.

Datatype Classes
Class	Summary
anyURI	A Uniform Resource Identifier.
DataType	A reference to a data type.
fieldName	An HTTP header field name.
fieldValue	An HTTP header field value.
mediaType	A media content type.
paramName	An XML name token.
RepresentationType	A URI that refers to a type in a schema.
statusCode	An HTTP status code.
string	A character string.
Thing	An rdfs:Resource.
uriTemplate	A URI template.
verb	An HTTP method name.

anyURI

A Uniform Resource Identifier. The URI conforms to XML Schema Part 2: Datatypes (anyURI)

DataType

A reference to a data type. The reference must be resolvable to a URI that identifies the data type specification, given in XML Schema.

fieldName

An HTTP header field name. The name matches the field-name production of RFC 2616 Section 4.2.

fieldValue

An HTTP header field value. The value matches the field-value production of RFC 2616 Section 4.2.

mediaType

A media content type. A media type conforming to RFC 2616 Section 3.7.

paramName

An XML name token. The token conforms to XML Schema Part 2: Datatypes (NMTOKEN)

RepresentationType

A URI that refers to a type in a schema. The type definition within the schema specifies the syntax for the representation.

statusCode

An HTTP status code. A numeric HTTP status code as defined in RFC 2616 Section 6.1.1.

string

A character string. The character string conforms to XML Schema Part 2: Datatypes (string)

Thing

An rdfs:Resource.

uriTemplate

A URI template. The template conforms to RFC 6570

verb

An HTTP method name. Method names are found in RFC 2616 Section 5.1.1 (e.g. GET, POST, PUT, DELETE).