The document outlines the setup and configuration of REST services for accessing and editing a semantic graph database. It covers the necessary components, including server configuration, service and resource creation, and methods for handling HTTP requests. It also provides examples for built-in resources and homework tasks to reinforce the learning of REST service implementation.

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i-views University
Part 12: REST Service

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REST-Service
Patrick Closhen
Software Engineer
intelligent views gmbh
Today‘s Speaker

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REST-Service
Agenda
1. Introduction
2. Set-up issues
3. Configuring services
4. Homework

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1. Introduction
• Access and edit the semantic graph database via REST-Services
• Specify what can be seen and how it is displayed and edited via view configurations
• Make use of pre-defined resources
• Compose the back-end part for your own web-frontends

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REST-Service
Architecture
mediator
Web-frontend
http/https
REST-bridges
internal/http

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REST-Service
2. Set-up issues
• REST component: provides needed schema for services and resources
• Needs to be added in the Admin-Tool
• Configuration of front-ends: front-ends need to be connected to the bridges to render the served data
• Additional settings: your semantic graph database must have a user type that provides a password
attribute. This will be set up if you choose a user type within the settings in the knowledge builder, tab
„system“, item „rights“ (needed for authentication)

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Set-up issues
• Configuration of REST-bridges: configuration file bridge.ini is needed to specify which services are
going to be provided by the application
• Define the host [and port] of the server of the semantic graph database
• Define the name of the volume to be accessed
• Define the port over which the services will be available
• Define the services this instance of REST-bridge is going to serve

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3. Configuring services
• The installation of the REST component in the semantic graph database provides schema for service
and resource objects and installs the built-in resources
• Services
• They bundle resources to differentiate between different sets of capabilities as needed
• They need to be identified in the configuration of the bridge(s) to be available
• Resources
• They define what requests are available within the containing service (path) and how they are executed
• They define which HTTP-Method is used
• They declare whether to use authentication or not
• They define the parametrization of the request

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The REST service description
List of REST services
Service details

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Building blocks (REST service)
- Collection of resources
- Start of the URL path
- Services are configured in the
bridge.ini
[Default]
host=localhost
loglevel=10
[KHTTPRestBridge]
volume=Schulungsnetz
port=8815
services=music

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Building blocks (REST resource)
- Remainder of the URL-path
- Multiple Types
- Script resource
- Built-in resource
- Static resource
- Defines a path-pattern
- Parts in {curlyBrackets} are
placeholders for variables

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Building blocks (REST method, script resources only)
HTTP method
- GET, POST, PUT, DELETE…
Input/Output media type
- mime-types of accepted and
produced data
Script
- JavaScript that is executed to
compute the response
Transaction
- Read, Write, Controlled by
script

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Building blocks (REST parameter)
Location (Style)
- Path-variables
- Query-parameters
- HTTP headers
Datatypes coercion
- String, Integer etc.
- Special k:element
Repeating
- ?album=abc&album=cde
Fixed value
- default if parameter is absent
Required
- Error, if parameter is absent

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Building a resource (Add a resource)
The left button always adds a new
configuration object

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Building a script resource (Add a method)
The left button always adds a new
configuration object

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Building a script resource (Select a media type)
The left button always adds a new
configuration object

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REST-Service
Building a script resource (Select a media type)
The left button always adds a new
configuration object

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REST-Service
Building a script resource (Create a new JavaScript)
The left button always adds a new
configuration object

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REST-Service
Building a script resource (Create a new JavaScript)
The left button always adds a new
configuration object

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REST-Service
Building a script resource (Create a new JavaScript)
A stub for the JavaScript is
generated
„parameters“ are the REST
parameters defined in framework

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Building a script resource (Add a parameter)
The left button always adds a new
configuration object

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REST-Service
Building a script resource (Choose a parameter type)
The left button always adds a new
configuration object

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REST-Service
Building a script resource (Compute something)
The left button always adds a new
configuration object

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Building a script resource (Test the script)
The left button always adds a new
configuration object

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Opening the request in the browser
http://localhost:8815/music/album/ID1405_147386337/songs

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Built-in Resources
• Pre-defined resources that are available in the system
• Can be added to services
• Cover often encountered use-cases:
• Accessing and changing blob attributes
• Object lists of objects, including sorting and filtering
• Accessing print templates and rendering with specified objects
• Accessing the configured icons of types
• ViewconfigMapper uses 3 types of built-in resources

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Built-in Resources
Creating a built-in resource:
• Select the service into which the resource is to be embedded
• Click on the „Create new Instances of REST resource“ button
• Choose „Instances of Built-in Resource“
• Choose the desired kind of built-in Resource
• ActionResource
• BlobResource
• EditorConfigResource
• ObjectListPrintTemplateResource
• ObjectListPrintTemplateResourceWithFilename
• ObjectListResource
• TopicIconResource

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Built-in Resources
/blob/{blobLocator}
Allowed methods: GET, POST, PUT
Parameters:
• blobLocator: e.g. id of the blob attribute whose contents are to be retrieved or set
• binaryKey: used in multi-part messages to identify the corresponding part of the data
• overrideContentType: tells the database what content type it really has to expect
• uploadOnly: boolean which controls whether the data will only be sent to the database, result is a
JSON string that allows to refer to the created blob and set it in another REST call
Examples:
GET http://localhost:8815/default/blob/ID43_1234567 fetches a blob from i-views
PUT http://localhost: 8815/default/blob/PP~ID43_1234~ID45_2345 creates a new blob at object with first id of
property type with second id (Possible Property Locator syntax)

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Builtin-in Resources
/topicIcon/{topicID}
Allowed methods: GET
Parameters:
• topicID: (required) id of the object
• size: (optional) desired integer pixel size of the icon, expanded to point
• extensions: (optional) boolean, true allows returning icons of extension objects of the chosen topic
Examples:
GET http://localhost:8815/default/topicIcon/ID43_1234?size=10

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Built-in Resources
/{typeLocator}/objectList
Allowed methods: GET
Parameters:
• typeLocator: (required) id of the type whose objects are to be displayed in table form
• name: (opt.) name of the object list configuration to be used
• application: (opt.) name of the application which determines the view config
• elements: (opt.) comma-separated locators for elements for the table
• elementsPath: (opt.) kpath-expression that will be used to determine start objects
• startTopic: (opt.) id of topic to use as starting point for elementsPath
• sort: (opt.) expression for sorting (multi-sort possible)
• filter: (opt.) expression for filtering steps

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Built-in Resources
Parameters cont.:
• disableInheritance: (opt.) boolean to prevent descending into sub-types
• type: (opt.) string param to choose whether to display objects or sub-types of the given starting type
Remark: Although the parameter „application“ is optional it is essential for accessing the correct object
list view configuration. Therefore always associate the table with the pre-defined application „REST“ and
add the parameter „application=REST“ to the request
Examples:
GET http://localhost:8815/Person/objectList?name=test&application=REST
render all persons using object list config named „test“
GET http://localhost:8815/Person/objectList?sort=-1&filter=1~equals~g*
sort the table in descending order of values in column 1 and filter with „g*“ in the first column

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Built-in Resources
/{conceptLocator}/objectList/printTemplate/{templateLocator}
Allowed methods: GET
Parameters:
• same as objectList before
• templateLocator: (required) id of the print template object to be used to generate the output
Examples:
GET http://localhost:8815/default/Person/objectList/printTemplate/ID_46_3456
render all Person objects using the referenced print template

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Built-in Resources
/{conceptLocator}/objectList/printTemplate/{templateLocator}/{filename}
Same as above, additional parameter „filename“ is not read, serves only to distinguish requests in the
web browser

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Built-in Resources
Configuring the built-in resources:
• Built-in resources encapsulate specific functionality, the only thing left to configure is whether this
instance of resource needs authentication
• Additionally built-in resources offer the capability to define scripts which are executed before and
after the request is computed to allow for changes in advance and to further influence the response
that the request computed
• Preprocessing Script
• Postprocessing Script
• These scripts are created and maintained analogous to the scripts that are embedded into script REST
resources, they only provide different function headers

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Static File Resources
Static content can be referenced from within the REST bridge.
• place content in sub-directories of the installation directory of the REST bridge
• declare the path pattern of the intended resources to map the relevant sub-directories
Example:
• installation directory of the bridge includes directory „icons“ which contains the needed files
• create a static file resource with path pattern „icons“, embed it into the service „test“
• request will look like this:
• GET http://localhost:8815/test/icons/file.png

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Homework
1. Define a script-resource that accepts a string parameter and responds by returning the given string
2. Define a script-resource that allows to edit an attribute of your choice at an object
• Parameters for value an to identify the object that is going to be edited
• Method
• Transaction control!
• Error handling (e.g. in case of attribute value type mismatch)
3. Define a built-in resource that returns an object list of all songs
• Remember to refer the specified object list to the application REST with the relation „apply in“!

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Advanced: REST-Service
Send your questions to:
contact-webinar@i-views.com
Consultation hours: Every Wednesday
Thank you for visiting
i-views University

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Advanced: REST-Service
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