Rdf Constants Laravel Package

Getting Started

Minimal Setup

1. Installation:

   composer require zozlak/rdf-constants
   

   Add to composer.json if not using autoloading:

   "autoload": {
       "psr-4": {
           "App\\": "app/",
           "Zozlak\\RdfConstants\\": "vendor/zozlak/rdf-constants/src/"
       }
   }
   

   Run composer dump-autoload.

2. First Use Case: Access constants via the Zozlak\RdfConstants\Rdf facade or class:

   use Zozlak\RdfConstants\Rdf;
   
   // Example: Get a SKOS constant
   $collectionUri = Rdf::SKOS_COLLECTION;
   

3. Key Classes:

   • Rdf (facade) – Primary entry point for all constants.
   • RdfConstants (class) – Direct access to all namespaced constants (e.g., RdfConstants::DC_TITLE).

Implementation Patterns

Common Workflows

1. Semantic Web Integration: Use constants to define RDF/SKOS/DCAT properties in models or API responses:

   $model->properties = [
       Rdf::DC_TITLE => 'My Resource',
       Rdf::SKOS_PREF_LABEL => 'Preferred Label',
   ];
   

2. Dynamic Property Handling: Validate or sanitize RDF properties using constants:

   $allowedProperties = [
       Rdf::DC_TITLE,
       Rdf::DC_DESCRIPTION,
       Rdf::SKOS_NOTE,
   ];
   
   if (!in_array($request->property, $allowedProperties)) {
       abort(400, 'Invalid RDF property');
   }
   

3. SPARQL Query Building: Construct queries with constants for consistency:

   $query = "PREFIX skos: <{$rdf->SKOS_NAMESPACE}> SELECT ?label WHERE { ?resource skos:prefLabel ?label }";
   

4. API Response Normalization: Standardize responses using RDF constants as keys:

   return response()->json([
       'title' => $resource->title,
       'dcterms_title' => Rdf::DC_TITLE, // Metadata for clients
   ]);
   

5. Namespace Resolution: Extract namespaces dynamically for configuration:

   $namespaces = [
       'skos' => Rdf::SKOS_NAMESPACE,
       'dcterms' => Rdf::DC_NAMESPACE,
   ];
   

Integration Tips

• Laravel Eloquent: Use constants in accessors/mutators for RDF-aware models:

  public function getSkosLabelAttribute()
  {
      return $this->attributes[Rdf::SKOS_PREF_LABEL] ?? null;
  }
  

• Form Requests: Validate RDF properties in FormRequest classes:

  public function rules()
  {
      return [
          'property' => 'required|in:'.implode(',', [
              Rdf::DC_TITLE,
              Rdf::SKOS_ALTERNATE,
          ]),
      ];
  }
  

• Service Providers: Bind constants to the container for dependency injection:

  $this->app->bind('rdf.constants', function () {
      return new \Zozlak\RdfConstants\Rdf();
  });
  

Gotchas and Tips

Pitfalls

1. Namespace Conflicts: Avoid collisions with custom constants. Prefix usage:

   // Bad: Assume `DC_TITLE` is unique.
   // Good: Use `Rdf::DC_TITLE` explicitly.
   

2. Deprecated Constants: Check for typos (e.g., SKOS_COLLECTION was fixed in v1.2.1). Verify with:

   dd(get_declared_constants(true)['user']['rdf'] ?? []);
   

3. Namespace URIs: Constants like SKOS_NAMESPACE return full URIs (e.g., http://www.w3.org/2004/02/skos/core#). Trim trailing # if needed:

   $prefix = rtrim(Rdf::SKOS_NAMESPACE, '#');
   

4. Immutable Constants: Constants are static. For dynamic values (e.g., locale-specific labels), extend the class:

   class ExtendedRdf extends \Zozlak\RdfConstants\Rdf {
       public static function SKOS_LABEL($lang = 'en') {
           return "http://www.w3.org/2004/02/skos/core#{$lang}Label";
       }
   }
   

Debugging

• Verify Constants: Dump all available constants to debug:

  dd((new \Zozlak\RdfConstants\Rdf())->getConstants());
  

• SPARQL Validation: Test queries with a tool like W3C SPARQL Validator to ensure constants resolve correctly.

Extension Points

1. Custom Namespaces: Extend the base class to add domain-specific constants:

   class AppRdf extends \Zozlak\RdfConstants\Rdf {
       public const MYAPP_NAMESPACE = 'http://example.com/ns#';
       public const MYAPP_CUSTOM_PROP = self::MYAPP_NAMESPACE . 'customProp';
   }
   

2. Localization: Override label constants for multilingual support:

   class LocalizedRdf extends \Zozlak\RdfConstants\Rdf {
       public const SKOS_PREF_LABEL = 'http://example.com/skos/prefLabel_'.app()->getLocale();
   }
   

3. Configuration: Load constants from a config file for environment-specific overrides:

   // config/rdf.php
   return [
       'namespaces' => [
           'skos' => env('RDF_SKOS_NAMESPACE', Rdf::SKOS_NAMESPACE),
       ],
   ];
   

Performance

• Caching: Cache resolved URIs if used frequently (e.g., in loops):

  $cache = Cache::remember('rdf_constants', 60, function () {
      return (new \Zozlak\RdfConstants\Rdf())->getConstants();
  });