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In order to interpret an XML response from a REST web service, Blueriq needs to import an XSD. In contrast to SOAP, there may not be an explicit contract available for REST. You can use the API of the REST service to get XSD files.

Close your project and go to File → Import → Import XSD and provide the location of the XSD file. If you have multiple files (for example: your XSD is importing/including an XSD schema), provide a ZIP file with all needed files. This is essentially the same as importing a WSDL (4. Calling a SOAP service). Select the project for the import and you can choose whether to create a new module, or overwrite an existing one.

The option 'Generate Domain' will automatically generate a domain model for you, based on the XSD schema. When this button is checked, entities, attributes and relations are created based on the type definitions in the XSD. When using an existing module, there may already be a domain model present, that uses identical names as in the XSD. When overwriting, conflicting elements are not created. Obviously, these problems do not occur if you use a new module.

When 'Generate Domain' is unchecked, no domain model is generated for you. In that case, you can later map the elements from the XSD to your own domain (explained later). In general, it is advised to use a separate module in order not to mix the domain model for the web service with the domain of your business.

You should get the message that the import was successful.

Open your project and go the module which contains the web service. The module now has a Schema Set. This item can be found in the bar on the left side of the screen, as can be seen below.

The Schema Set defines which entities, attributes and relations are used by the web service (they map the XSD to the domain model). This works exactly the same for REST and SOAP, and the description can be found here: 4. Calling a SOAP service.

Using a domain schema

The domain schema lets you define a representation of the elements in the application, and that is used for the communication with a web service. The purpose of this representation is to define what items are needed to accurately describe an element (for example the representation of person is his first name, followed by his second name.). You can see the domain schema as a sort of contract of the communication. You start with an entity that represents the begin and the end of the message. For every attribute/relation you can select a name, what datatype it is, if it is required within the message and if it is multivalued. This contract should be set up to reflect the message that is sent, but it can be different to the internal Blueriq domain. For instance, your contract uses a multivalued attribute. Your application always has one value for this attribute however, so it is not multivalued. When sending a message, it is no problem to insert a single-valued attribute in a multivalued entry in the domain schema. It will just be sent as a list with only one entry. You have to be careful if it is the other way around, storing a list with possibly more values on a single valued attribute will not work.

An important point to note is that the domain schema is independent of the language that is used for the communication, and projects can add implementations of any representation not covered out-of-the-box (out of the box we offer JSON and XML). Blueriq uses the domain schema that you define in Studio as basis to create a message to a web service or to read a message from a web service. Using the domain schema Blueriq generates a JSON or XML message in a straightforward way during runtime. To inspect the translation to JSON or XML, click the preview button in Studio. 

In the example below, the status of an airport is represented by a certain set of attributes, starting with the delay.

In contrast to importing a WSDL, no service definition is automatically generated. You have to manually define how the REST service is called. This section explains how you can configure a REST service object in Studio that uses either an XSD or domain schema.

Create a new REST service in Studio (the lowest button on the left sidebar, see the screenshot above) and give it a name. Next, you need to specify the location of the REST service. This is a URL. You can already specify fragments and arguments here, but then you cannot change them later. For example, check http://services.faa.gov/airport/status/IAD?format=xml. In this case, airport, status and IAD are dynamic fragments and can change, depending on input by the user. You would only use http://services.faa.gov/ as location in this case.

Now you specify how the communication is specified. This can either be a Domain schema, or an XSD schema set. You have to choose one XSD schema set here that has to include everything for the entire web service. In contrast, by choosing a domain schema, you will later choose what domain schema to use for every separate method.

You can specify as many operations as you need, by pressing on the plus icon. Give every operation a unique name.

Request

1. If you want to dynamically change the address or send custom headers or body in your message, you need to specify a singleton entity from where the information is gathered.
2. Here the URL is shown that will be called. Items within {} are dynamic and determined at runtime.
3. You can add static fragments which are always the same.
4. You can also add dynamic fragments which are filled by attributes of the request entity.
5. You can specify arguments of your request the same way.
6. There are 4 different HTTP methods: GET, POST, PUT and DELETE. Most likely, the web service works with the GET method. This method does not alter the state of the web service and just asks for information. 

Response

Now you can specify the format of the response message. If you need to set headers, then you can do so at (1) in the same way you set arguments or fragments for the request. For example, you can store the status header in the profile, so that you can show a different message to the end user depending on the status code (e.g., 'Try again later' when the web service had a time-out). How this could look like in studio is shown in the screenshot below. If you need to send information in the body of the message, for example with a POST message, then you can specify this now. This screen looks different depending on whether you send information using an XSD schema set or a domain schema.

We explain the XSD schema set first. If you have a SimpleType in the schema, then you fill in an attribute at (4). If it is a complexType, then first choose which entity will be sent at (2) and then your attribute field (4) will switch to a relation field. Fill in the name of the relation between your singleton response entity and your data entity. Custom Schema Elements (3) are ways to fill in your schema in a different way other than with data from your profile. It is not needed at the moment (An example is a justification tree)

When using a domain schema, you now simply select the domain schema that you want to use to send information (2). Furthermore, you have to select a body relation (3). This is a relation between the singleton response entity of your message and the entity that is chosen as the root entity in your domain schema.

This is similar to SOAP (4. Calling a SOAP service).

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