Virtuoso provides services that render Entity Descriptions using HTML descriptions. These descriptions provide human-readable representations of RDF-based Entity Relationships stored in a Virtuoso-managed Knowledge Graph.
Each of these services is packaged in a Virtuoso Application Distribution (VAD) package and deployed via an endpoint, following VAD installation.
/about— endpoint for the Entity Description Service packaged with the Sponger Middleware Module as part of thecartridges_dav.vadpackage/describe— endpoint for the Entity Description Service packaged with the Faceted Browser Module as part of thefct_dav.vadpackage
/about Service
The /about/ endpoint is mapped to a /rdf/desc/description.vsp (Virtuoso’s equivalent of a PHP or ASP page) which provides an Entity Description using a variety of negotiable document types. For instance, if a URL contains the pattern /about/html, it presents an Entity Relationship Description using an HTML document that associates a single Entity with all of its Properties.
Features include —
- Entity Description Presentation
- Linked Data Principles applied to data imported from external sources (i.e., sponging for progressive Knowledge Graph updates)
- Entity Descriptions using a variety of negotiable document types (e.g., HTML, HTML+ Various Structured Data Islands, RDF-Turtle, JSON-LD, JSON, CSV, etc.)
This service is a preconfigured mapping of a URL to a VSP that’s installed as part of the Sponger Package (cartridges_dav.vad). It is also similar to the DBpedia skin, but with the addition of “on the fly” dereferencing of URIs when associated with external data sources.
Example
- Musicbrainz Example using URIBurner — a live Virtuoso Instance
/describe Service
The /describe/ endpoint is mapped to a /fct/rdfdesc/description.vsp Virtuoso Server Page (Virtuoso’s equivalent of ASP) which provides an Entity Description using a variety of negotiable document types. For instance, if a URL contains the pattern /describe={Entity-URI}, it presents an Entity Relationship Description using an HTML document that associates a single Entity with all of its Properties.
Features include —
- Entity Description Presentation
- Faceted Browsing, i.e., data exploration informed by Entity Relationship Type Semantics, e.g., clicking on
rdf:typeproperty values resolve to all instances of an associated class; likewise, clicking on a property reveals its accepted domains and ranges, which also provide exploration pathways using the follow-your-nose pattern - Sponging is included as an option for progressive Knowledge Graph updates
- Entity Descriptions using a variety of negotiable document types (e.g., HTML, HTML+ Various Structured Data Islands, RDF-Turtle, JSON-LD, JSON, CSV, etc.)
Example
Note
The description.vsp pages mapped from /about/ and /describe/ are fundamentally different in the following ways:
- External Data Imports (a/k/a “Sponging”) occur each time you click on a link when using
/about/, but not when using/describe/, which includes a “sponger” or “import” link for explicit imports - Clicking on an
rdf:typeproperty resolves all instances of the value of said property when using/describe/, but not when using/about/
Linked Data Deployment
You can easily deploy Linked Data using Virtuoso by creating re-write rules that map HTTP requests to either the /about/ or /describe/ endpoints. This provides a very simple option for Linked Data Deployment when using any Virtuoso instance to which the relevant VAD packages have been installed.