Introduction

This tutorial shows how you can build a Knowledge Graph based on input data from hierarchical sources like a JavaScript Object Notation file (.json) or an Extensible Markup Language file (.xml).

The complete tutorial is available as a project file (XML) and a project file (JSON). You can import these projects

  • by using the web interface (Create → Project → Import project file) or
  • by using the command line interface

    cmemc -c my-cmem project import tutorial-xml.project.zip xml-transformation
    BASH
    cmemc -c my-cmem project import tutorial-json.project.zip json-transformation
    BASH

The documentation  consists of the following steps, which are described in detail below:

The following material is used in this tutorial:

  • Sample vocabulary which describes the data in the JSON and XML files: products_vocabulary.nt

  • Sample JSON file: services.json

    [
        {
            "Price": "748,40 EUR",
            "ProductManager": "Lambert.Faust@company.org",
            "Products": "O491-3823912, I965-1821441, Z655-3173353, ...",
            "ServiceID": "Y704-9764759",
            "ServiceName": "Product Analysis"
        },
        {
            "Price": "1082,00 EUR",
            "ProductManager": "Corinna.Ludwig@company.org",
            "Products": "Z249-1364492, L557-1467804, C721-7900144, ...",
            "ServiceID": "I241-8776317",
            "ServiceName": "Component Confabulation"
        },
        ...
    ]
    JS
  • Sample XML file: orgmap.xml

    Preview of the XML sample
    <orgmap>
        <dept id="73191" name="Engineering">
            <manager>
                <email>Thomas.Mueller@company.org</email>
                <name>Thomas Mueller</name>
                <address>Karl-Liebknecht-Straße 885, 82003 Tettnang</address>
                <phone>+49-8200-38218301</phone>
            </manager>
            <employees>
                <employee>
                    <email>Corinna.Ludwig@company.org</email>
                    <name>Corinna Ludwig</name>
                    <address>Ringstraße 276</address>
                    <phone>+49-1743-24836762</phone>
                    <productExpert>Memristor, Gauge, Encoder</productExpert>
                </employee>
                <employee>
                    <email>Karen.Brant@company.org</email>
                    <name>Karen Brant</name>
                    <address>Friedrichstraße 664, 30805 Willich</address>
                    <phone>(00530) 5040048</phone>
                    <productExpert>Inductor</productExpert>
                </employee>
    			...
            </employees>
            <products>
                <product id="Z249-1364492" />
                <product id="O184-6903943" />
                <product id="V404-9975399" />
                <product id="F344-7012314" />
                <product id="N463-8050264" />
                <product id="M605-5951566" />
                <product id="N733-1946687" />
            </products>
            <services>
                <service id="I241-8776317" />
                <service id="D215-3449390" />
            </services>
        </dept>
        <dept id="22183" name="Product Management">         
    		...
    	</dept>
    	...
    </orgmap>
    XML

Register the vocabulary

The vocabulary contains the classes and properties needed to map the source data into entities in the Knowledge Graph.

  1. In Corporate Memory, click Vocabularies in the under EXPLORE in the navigation on the left side of the page.

  2. Click Register new vocabulary on the top right of the Vocabulary catalog page in Corporate Memory.
  3. Define a Name, a Graph URI and a Description of the vocabulary.
    In this example we will use:
    • Name: Product Vocabulary
    • Graph URI: http://ld.company.org/prod-vocab/
    • Description: Example vocabulary modeled to describe relations between products and services.
  4. Click REGISTER.

Upload the data file

To add the data files, click Projects under BUILD in the navigation on the left side of the page. Follow the steps below for adding JSON and XML datasets.

  1. Click Create at the top of the page.  
  2. In Create new item window, select JSON and click Add. 

  3. Define a Label for the dataset and upload the services.json file. You can leave all the other fields at default values. 

  4. Click Create
  1. Press the Create button and select XML

  2. Define a Label for the dataset and upload the orgmap.xml example file. You can leave all the other fields at default values. 

  3. Click Create.

Create a Knowledge Graph

  1. Click Create at the top of the page.  
  2. In Create new item window, select Knowledge Graph and click Add. The Create new item of type Knowledge Graph window appears.  
  3. Fill in the required details such as Label and Description.  


Define a Label for the Knowlege Graph and provide Graph uri. You can leave all the other fields at default values. 

In this example we use:

  • Name: Service Knowledge Graph

  • Graph: http://ld.company.org/prod-instances/

Define a Label for the Knowledge Graph and provide Graph uri. You can leave all the other fields at default values. 

In this example we will use:

  • Name: Organization Knowledge Graph

  • Graph: http://ld.company.org/organization-data/

Create a Transformation

The transformation defines how an input dataset (e.g.: JSON or XML) will be transformed into an output dataset (e.g.: Knowledge Graph).

  1. Click Create in your project.  
  2. On the Create New Item window, select Transform and click Add to create a new transformation.

  3. In the Create new item of type Transform window, enter the required fields. 


For this example, enter the following:

  • Name: Create Service Triples

  • (optional) Description: Lifts the Service file into the Knowledge Graph
  • Select the Source Dataset: Services JSON
  • Select the Output Dataset: Service_Knowledge_Graph

Click Create.

For this example, enter the following:

  • Name: Create Organization Triples
  • (optional) Description: Lifts the Orgmap XML file into the Knowledge GraphOrgmap XML
  • Select the Source Dataset: Orgmap XML
  • Type: dept (define the Source Type, which defines the XML element that should be iterated when creating resources)
  • Select the Output Dataset: Organization_Knowledge_Graph

Click Create.

4.  Expand the menu by clicking the arrow on the right side of the page to expand the menu.

5.  Click Edit to create a base mapping.
     
6. Define the Target entity type from the vocabulary, the URI pattern and a Label for the mapping.


Target Entity Type defines the class that will be instantiated when the mapping rule is applied.

The URI pattern that defines the URI that shall be generated for each individual

  •  http://ld.company.org/prod-inst/ is a common prefix for the instances in this use case,
  • service-instances/ complements the instances prefix by adding a common prefix for all service instances
  • and finally {ServiceID} is a placeholder that will resolve to the json-key ServiceID (e.g. "ServiceID": "Y704-9764759")

In this example we will use:

  • Target Entity Type: Service

  • URI Pattern: http://ld.company.org/prod-inst/service-instances/{ServiceID}
  • An optional Label: Service

Click SAVE.

Example RDF triple in our Knowledge Graph based on the mapping definition:

<http://ld.company.org/services-instances/Y704-9764759> <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://ld.company.org/prod-vocab/Service> 
TEXT

Target Entity Type defines the class that will be instantiated when the mapping rule is applied: Department

The URI pattern that defines the URI that shall be generated for each individual: http://ld.company.org/department/{@id}

  • http://ld.company.org/department/ is a common prefix for the department instances in this use case,
  • and finally {@id} is a placeholder that will resolve the XML attribute of the XML tag dept, which was configured as the Source Type of this transformation (see previous steps)

In this example we will use:

  • Target Entity Type: Department
  • URI Pattern: http://ld.company.org/department/{@id}
  • An optional Label: Department

Click Save.

Example RDF triple in our Knowledge Graph based on the mapping definition:

<http://ld.company.org/department/73191 <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://ld.company.org/prod-vocab/Department> 
TEXT

      7. Evaluate your mapping by pressing on the button in the Examples of target data property to see at most three generated base URIs.
           
We have now created the Service entities in the Knowledge Graph. Next we will now add the name of our entity.

     8. Click the circular blue + icon on the lower right and select Add value mapping.
         

Define the Target property, the Data type, the Value path (column name) and a Label for your value mapping.

In this example, enter the following:

  • Target Property: has product manager

  • Data type: StringValueType
  • Value path: ProductManager/name
    • which corresponds to the following element in the json-file: [ {"ProductManager": {  "name": "Corinna Ludwig"} ... } ...]
  • An optional Label: has Product Manager

Click Save.

Define the Target property, the Data type, the Value path (column name) and a Label for your value mapping.

In this example we will use:

  • Target Property: name

  • Data type: StringValueType
  • Value path: dept/@name
    • which corresponds to the department name attribute in the XML file
  • An optional Label: department name

Click Save

By clicking on the button in the Examples of target data property, you can get a preview for 3x value mapping to be created.

Evaluate a Transformation

Click Transform evaluation to evaluate the transformed entities. 

Execute a Transformation to build a Knowledge Graph

  1. Click Transform execution
  2. Press the button and validate the results. In this example, 9x Service entities were created in our Knowledge Graph based on the mapping.
  3. You can click Knowledge Graphs under EXPLORE to (re-)view of the created Knowledge Graphs
  4. Enter the following URIs in the Enter search term for JSON and XML respectively. 
    • JSON / Service: http://ld.company.org/prod-instances/
    • XML / Department: http://ld.company.org/organization-data/