When a subject-matter-expert (SME) describes their data domain they use English language. In response we give them visually beautiful, but often undecipherable, diagrams. Here we propose an alternative: a ‘word-model’ that describes the model in structured English without loss of accuracy or completeness.

Creating an ontological model invariably involves a subject-matter-expert (SME) who has an in-depth knowledge of the domain to be modelled working together with a data modeler or ontologist who will translate the domain into an ontological model.

When a subject-matter-expert (SME) is in discussion with a data modeler, they will be describing their information using English language:

“I have customers who are assigned to regions, and they create orders with a salesperson who prepares the order-details and assigns a shipper that operates in that region”

In response a data modeler will offer the subject-matter-expert (SME) an E-R diagram or an ontology graph!

Figure 1: Geek Model Diagrams

No wonder we are regarded as geeks! Although visually appealing, they are difficult for an untrained user to verify the model that the diagram is describing.

Instead we could document the model in a more easily consumed way with a ‘word-model’. This captures the same details of the model that are present in the various diagrams, but uses structured English and careful formatting as shown below.

aCustomer

  • places anOrder
    • made by anEmployee
      • who reports to anotherEmployee
      • and who operates in aTerritory
    • and contains anOrderDetail
      • refers to aProduct
        • which is supplied by aSupplier
        • and which categorized as aCategory
      • and is shipped by aShipper
      • and is assigned to aRegion
        • which has aTerritory
      • and belongs to aRegion

The basic principle is that we start at any entity, in this case ‘Customer’ and traverse the edges of the graph that describe that entity. At each new node we indent. Each line is a combination of the predicate and range class. No rules regarding order in which we visit the nodes and edges. No rules regarding depth. The only rule should be that, if we want a complete word-model, the description traverses all edges in one direction or the other.

These word-models are useful in the model design phase, as they are easy to document using any editor. Since the word-model is in ‘plain English’, it is easy for a SME to verify the accuracy of the model, and mark up with comments and edits. However word-models are also easy to generate from an RDF/OWL model.

Enhancements to Word-Model

We can refine the contents of the word-model as we develop the model with the SME. We can also enhance the readability by decorating the word-model text with the following fonts:

Word-Model Legend
Italics indicate an instance of a class, a thing
Bold indicates a class
Underline is a predicate or property that relates instances of classes
BoldItalic is used for cardinality expressions

Level 1a: Add the categorization of entities

Rather than using an example of an entity, we can qualify with the class to which the sample entity belongs.

aCustomer, a Customer

  • places anOrder, an Order
    • made by anEmployee, an Employee
      • who reports to anotherEmployee, an Employee
      • and who operates in aTerritory, a Territory
    • and contains anOrderDetail, an OrderDetail
      • and refers to aProduct, a Product
        • which is supplied by aSupplier, a Supplier
        • and which is categorized as aCategory, a Category
      • and is shipped by aShipper, a Shipper
      • and is assigned to aRegion, a Region
        • which has aTerritory, a Territory
      • and belongs to aRegion, a Region

Level 1b: Add cardinality of predicates

We can also add the cardinality as a modifier between the predicate and the entity:

aCustomer

  • who places zero, one or more orders
    • each made by one anEmployee
      • who reports to zero or one anotherEmployee
      • and who operates in one or more aTerritorys
    • and each contains one or more anOrderDetails
      • which refers to one aProduct
        • which is supplied by one aSupplier
        • and which is categorized as one aCategory
      • and is shipped by one aShipper
      • and is assigned to one aRegion
        • which has one or more aTerritorys
      • and belongs to one aRegion

Level 2: Add categorization and cardinality

Of course we can combine these extensions into a single word-modol as shown below.

aCustomer, a Customer

  • who places zero, one or more orders, each an Order
    • each made by one anEmployee, an Employee
      • who reports to zero or one anotherEmployee, an Employee
      • and who operates in one or more aTerritorys, each a Territory
    • and each contains one or more anOrderDetails, each an OrderDetail
      • which refers to one aProduct, a Product
        • which is supplied by one aSupplier, a Supplier
        • and which is categorized as one aCategory, a Category
      • and is shipped by one aShipper, a Shipper
      • and is assigned to one aRegion, a Region
        • which has one or more aTerritorys, each a Territory
      • and belongs to one aRegion, a Region

Despite the completeness of what is being described by this word-model, it is still easy to read by SMEs.

Auto-generation of Word-Model

Once the word-model has been formally documented in RDF/OWL, we can still use a word-model to document the RDF/OWL by auto-generating a word-model from the underlying RDF/OWL ontology as shown below.

Figure 2: Word-Model

This was generated using a SPIN magic-property as follows:

select ?modelDefinition
{
   (model:Customer 4 false) :modelDefinition ?modelDefinition .
}

This auto-generation can go further by including the datatype properties associated with each entity as shown below:

Figure 3: Word-Model including datatype properties

This was generated using a SPIN magic-property as follows:

select ?modelDefinition
{
   (model:Customer 4 true) :modelDefinition ?modelDefinition .
}

Appendix

SPIN Magic Properties:

The following SPIN properties were defined for auto generation of the word-model in HTML format:

classProperties

SELECT ?classProperties
WHERE {
{SELECT  ?arg1   (    IF(?arg2CONCAT("(",?properties,")"),"") as ?classProperties) WHERE
    {
        SELECT ?arg1 ((GROUP_CONCAT(CONCAT("<i>", ?dataPropertyLabel, "</i>"); SEPARATOR=', ')) AS ?properties)
        WHERE {
           # BIND (model:Product AS ?arg1) .
            ?arg1 a ?class .
            FILTER (?class IN (rdfs:Class, owl:Class)) .
            ?arg1 rdfs:label ?classLabel .
            ?dataProperty a owl:DatatypeProperty .
            ?dataProperty rdfs:domain ?arg1 .
            ?dataProperty rdfs:label ?dataPropertyLabel .
        }
        GROUP BY ?arg1
    }
}
}

classDefinition

SELECT ?classDefinition ?priorPath
WHERE {
    {
        SELECT ?arg1 ?arg2  ((GROUP_CONCAT( ?definition; SEPARATOR='<br/>and that ')) AS ?classDefinition)  ((GROUP_CONCAT( ?pastPath; SEPARATOR='\t')) AS ?priorPath)
        WHERE {
           ?arg1 a ?class . FILTER( ?class in (rdfs:Class, owl:Class ))
            ?arg1 rdfs:label ?classLabel .
            ?objectProperty a owl:ObjectProperty .
            {
                        ?objectProperty rdfs:domain ?arg1 .
                        ?objectProperty rdfs:label ?objectPropertyLabel .
                        ?objectProperty rdfs:range ?nextClass .
                        ?nextClass rdfs:label ?nextClassLabel .   BIND(?objectProperty as ?property)
            }UNION{
                        ?objectProperty  owl:inverseOf ?inverseObjectProperty .
                        ?objectProperty rdfs:domain  ?nextClass.
                        ?inverseObjectProperty rdfs:label ?objectPropertyLabel .
                        ?objectProperty rdfs:range ?arg1 .
                        ?nextClass rdfs:label ?nextClassLabel .    BIND(?inverseObjectProperty as ?property)
            }UNION{
                        ?inverseObjectProperty  owl:inverseOf ?objectProperty .
                        ?objectProperty rdfs:domain  ?nextClass.
                        ?inverseObjectProperty rdfs:label ?objectPropertyLabel .
                        ?objectProperty rdfs:range  ?arg1 .
                        ?nextClass rdfs:label ?nextClassLabel .    BIND(?inverseObjectProperty as ?property)
            }
#Stop from going too deep
            BIND(?arg2 -1 as ?span) FILTER(?span>0). 
            ?nextClass a ?nextClassClass. FILTER( ?nextClassClass in (rdfs:Class, owl:Class ))
#,  odata4sparql:Operation))  .
#Do not process an already processed arc (objectProperty)         
            BIND(CONCAT(?arg4,"\t",?objectPropertyLabel) as ?forwardPath) FILTER( !CONTAINS(?arg4, ?objectPropertyLabel ))  
            (?nextClass ?span ?arg3 ?forwardPath ) :classDefinition (?nextClassDefinition  ?nextPath).           
#Do not include if arc (objectProperty) appears already   
            FILTER(  !CONTAINS(?nextPath, ?objectPropertyLabel )) BIND(CONCAT( ?objectPropertyLabel, IF(?nextPath="","",CONCAT("\t",?nextPath))) as ?pastPath)
                                    (?nextClass ?arg3) :classProperties ?nextClassProperties .
            BIND (CONCAT("<u>",?objectPropertyLabel , "</u> <b>", ?nextClassLabel, "</b>",  ?nextClassProperties, IF ((?nextClassDefinition!=""), CONCAT("<br/><blockquote>that ",  ?nextClassDefinition, "</blockquote>"), "")  ) as ?definition)
        }
        GROUP BY ?arg1 ?arg2
    } .
}

modelDefintion

SELECT ?modelDefinition
WHERE {
    {
        SELECT ?arg1 ?arg2 ?arg3 ((CONCAT("<b>", ?classLabel, "</b>", ?nextClassProperties, "<blockquote>that ", ?classDefinition, "</blockquote>")) AS ?modelDefinition)
        WHERE {
           # BIND (model:Order AS ?arg1) .  BIND (4 AS ?arg2) . BIND (false AS ?arg3) .
            ( ?arg1 ?arg2 ?arg3 "") :classDefinition (?classDefinition "") .
            ( ?arg1 ?arg3 ) :classProperties ?nextClassProperties .
            ?arg1 rdfs:label ?classLabel .
        }
    } .
}

Usage

The following will return the HTML description of the model, starting with model:Customer, stopping at a depth of 4 in any direction, and not including the datatypeproperty definition.

select ?modelDefinition
{
   (model:Customer 4 false) :modelDefinition ?modelDefinition .
}

Let’s face it, RDF Graph datastores have not become the go-to database for application development like MySQL, MongoDB, and others have. Why? It is not that they cannot scale to handle the volume and velocity of data, nor the variety of structured and unstructured types.

Perhaps it is the lack of application development frameworks integrated with RDF. After all any application needs to not only store and query the data but provide users with the means to interact with that data, whether it be data entry forms, charts, graphs, visualizations and more.

However application development frameworks target popular back-ends accessible via JDBC and, now we are in the 21century, OData. RDF and SPARQL are not on their radar … that is unless we wrap RDF with OData so that the world of these application development environments is opened up to RDF Graph datastores.

OData2SPARQL provides that Janus-inflexion point, hiding the nuances of the RDF Graph behind an OData service which can then be consumed by powerful development environments such as OpenUI5 and WebIDE.

This article shows how an RDF Graph CRUD application can be rapidly developed, yet without losing the flexibility that HTML5/JavaScript offers, from which it can be concluded that there is no reason preventing the use of RDF Graphs as the backend for production-capable applications.

A video of this demo can be found here: https://youtu.be/QFhcsS8Bx-U

Figure 1: OData2SPARQL: the Janus-Point between RDF data stores and application development

Rapid Application Development Environments

There are a great number of superb application development frameworks that allow one to create cross platform (desktop, web, iOS, and Android), rich (large selection of components such as grids, charts, forms etc) applications. Most of these are based on the MVC or MVVM model both of which require a systematic and complete (CRUD) access to the back-end data via a RESTful API. Now that OData has been adopted by OASIS, the number of companies offering explicit support for OData is increasing, ranging from Microsoft, IBM, and SAP. Similarly there are a number of frameworks, one of which is SAPUI5 which has an open source version OpenUI5.

OpenUI5

OpenUI5 is an open source JavaScript UI library, maintained by SAP and available under the Apache 2.0 license. OpenUI5 lets you build enterprise-ready web applications, responsive to all devices, running on almost any browser of your choice. It’s based on JavaScript, using JQuery as its foundation, and follows web standards. It eases your development with a client-side HTML5 rendering library including a rich set of controls, and supports data binding to different models (JSON, XML and OData).

With its extensive support for OData, combining OpenUI5 with OData2SPARQL releases the potential of RDF Graph datasources for web application development.

Web IDE

SAP Web IDE is a powerful, extensible, web-based integrated development tool that simplifies end-to-end application development. Since it is built around using OData datasources as its provider, then WebIDE can be used as a semantic application IDE when the RDF Graph data is published via OData2SPARQL.

WebIDE runs either as a cloud based service supplied free by SAP, or can be downloaded as an Eclipse ORION application. Since the development is probably against a local OData endpoint, then the latter is more convenient.

RDF Graph application in 5 steps:

  1. Deploy OData2SPARQL endpoint for chosen RDF Graph store

The Odata2SPARQL war is available here, together with instructions for configuring the endpoints: odata2sparql.v2

The endpoint is this example is against an RDF-ized version of the ubiquitous Northwind databases. This RDF graph version can be downloaded here: Northwind

  1. Install WebIDE

Instructions for installing the Web IDE Personal edition can be found here: SAP Web IDE Personal Edition

  1. Add OData service definition

Once installed an OData service definition file (for example NorthwindRDF) can be added to the SAPWebIDE\config_master\service.destinations\destinations folder, as follows

Description=Northwind

Type=HTTP

TrustAll=true

Authentication=NoAuthentication

Name=NorthwindRDF

ProxyType=Internet

URL=http://localhost:8080

WebIDEUsage=odata_gen

WebIDESystem=NorthwindRDF

WebIDEEnabled=true

  1. Create new application from template

An application can be built using a template which is accessed via File/New/Project from Template. In this example the “CRUD Master-Detail Application” was selected.

The template wizard needs a Data Connection: choose Service URL, select the data service (NorthwindRDF) and enter the path of the particular endpoint (/odata2sparql/2.0/NW/).

Figure 2: WEB IDE Data Connection definition

At this stage the template wizard allows you to browse the endpoint’s entityTypes and properties, or classes and properties in RDF graph-speak.

Since the Web IDE and OpenUI5 is truly model driven, the IDE creates a master-detail given the entities that you define in the next screen.

The template wizard will ask you for the ‘object’ entityType which in this example is Category. Additionally you should enter the ‘line item’ but in this case there is only one navigation property (aka objectproperty in RDF graph-speak) which is the products that belong to the category.

Note that this template allows other fields to be defined, so titls and productUnitprice were selected.

Figure 3: WEB IDE Template Customization

  1. Run the application

The application is now complete and can be launched from the IDE. Right-click the application and select Run/Run as/As web application:

Figure 4: Application

Even this templated application is not limited to browsing data: it allows full editing of the categories. Note that even the labels are derived from the OData endpoint, but of course they can be changed by editing the application.

Figure 5: Edit Category

Alternatively a new category can be added:

Figure 6: Create New Category

Next Steps

That’s it: a fully functional RDF Graph web application built without a single line of code being written. However we can chose to use this just as a starting point:

  1. Publish data views, the SPARQL equivalent of a SQL view on the data, to the OData2SPARQL endpoint.
    • These are particularly useful when publishing reports in OpenUI5, Excel PowerQuery, Spotfire, etc.
  2. Modify the model that is published via the OData2SPARQL endpoint
    • The model that is published is extracted from the schema defined in the endpoint configuration. Thus the schema can be changed to suit what one wants in the endpoint metamodel.
  3. Edit the templated application
    • The templated application is just a starting point for adaptation: the code that is created is nothing more than standard HTML5/JavaScript using the OpenUI5 libraries.
  4. Build the application from first-principles
    • A template is not always the best starting point, so an application can always be built from first-principles. However the OpenUI5 libraries make this much easier by, for example, making the complete metamodel of the OData2SPARQL endpoint available within the application simply by defining that endpoint as the datasource.