RDF Properties in the Framework

Now we will define the properties to be used in the application and which classes that use them.

Warning

Unlike a SQL field definition a property can be used in many rdf:Classes

Steps

  1. Start by adding the basic information about a property you will be using:

    schema:email a rdf:Property;

    rdfs:label “E-mail”; rdfs:comment “Electronic mail sent through a network to an individual” .

  1. Add a rdfs:domain tag for each class that uses the property:

    schema:email rdfs:domain schema:Person,
                         schema:Organization .

Note

The two rdfs:domain statements listed above state that the schema:email property will be used in both the schema:Person and schema:Organization rdf:Classes.

  1. Next specify the rdfs:range for the property. Remember this tells the framework which type of value should be in the object position of a triple:

    schema:email rdfs:range xsd:string .

  2. Now we need to specify more specific rules for the property. If we want to make it a required property for a rdf:Class we can add a kds:requiredByDomain tag.

    schema:email kds:requiredByDomain schema:Person .

Note

Since we only added a kds:requiredByDomain tag for the schema:Person class, the schema:Organization, which also uses the property will not require the property. To make it a required property for the schema:Organization class as well add:

schema:email kds:requiredByDomain schema:Organization.

Warning

If the property was specified as a Primary Key in the rdf:Class definition it is not necessary to make it a required property in the property definition. Primary Keys are required by definition. It will NOT cause a problem if a primary key is also specified as a required property.

  1. Define any security rules for the property:

    schema:email kds:propertySecurity [
            **kds:appliesTo schema:Person**
            acl:agent kdr:Admin-SG;
            acl:mode acl:Read
] ;

Note

The kds:appliesTo tag specifies which rdf:Class to apply the security setting. In this case adding the above means that the schema:email property when used in the schema:Person class can only be seen by the kdr:Admin-SG. However, when it is used in the schema:Organization class no such rules apply.

  1. The next major component is to tell the framework how to validate the property. This way we have consistancy when saving data:

    schema:email **kds:propertyValidation** [
            a kdr:EmailValidator
    ] .

See also

For a full listing of validators see the Validator section

  1. Now state how the application should process the data for the property. There are wide variety of actions that can be performed:

    schema:email kds:propertyProcessing [
  kds:appliesTo schema:Person ;
  a kdr:EmailVerificationProcessor
] .

Note

We are appling an email verification action only to the schema:Person class. If we wanted to apply it to all rdf:Classes that use the property we would leave that line out.

See also

The processor section lists all available processors and their specifications.

  1. Lastly, we can define a default pattern for how the property will appear in forms:

    schema:email kds:formDefault [
            kds:formFieldName "emailaddr";
            kds:formLabelName "Email Address";
            kds:formFieldHelp "Enter a valid email address.";
            kds:fieldType [
                    a       kdr:TextField
            ]
    ] .

Note

These can be overridden in the actual form specification. Defining a default here allows for easy insertion of the property into many forms without having to specify the basics about the field each time.

See also

For a detailed explanation and options see the Forms section

  1. Putting it all together would look like this:

    schema:email a rdf:Property;
        rdfs:domain     schema:Person;
        rdfs:domain schema:Organization;
        rdfs:range      xsd:string;
        rdfs:comment "email address.";
        kds:requiredByDomain schema:Person;
        kds:propertyProcessing [
          kds:appliesTo schema:Person;
                a kdr:EmailVerificationProcessor
        ];
        kds:propertyValidation [
                a kdr:EmailValidator
        ];
        kds:propertySecurity [
          kds:appliesTo schema:Person;
                acl:agent kdr:Self-SG;
                acl:mode acl:Read, acl:Write
        ] ;
        kds:formDefault [
                kds:formFieldName "emailaddr";
                kds:formLabelName "Email Address";
                kds:formFieldHelp "Enter a valid email address.";
                kds:fieldType [
                        a       kdr:TextField
                ]
        ] .

Next define the application settings!