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SPARQL interfaces

Thanks for the link, Juan.
Just curious, even if I know SPARQL, how do I (as a new user) know which properties and types there are in the data? And what URIs to use for what?"
(David asks!)

Check also the following mail thread. User-friendly visual SPARQL implementations follow.

1. OpenLink Ajax Toolkit

GPL

OAT (OpenLink AJAX Toolkit) is a JavaScript-based toolkit for browser-independent Rich Internet Application development. It includes a rich collection of UI Widgets/Controls, Event Management System, and a truly platform independent Data Access Layer called AJAX Database Connectivity.

OAT works in Gecko browsers (Firefox, Mozilla/SeaMonkey), IE6/7, Opera and Apple WebKit.

Note the OpenLink offers Virtuoso.

Provides an SVG-based RDF graph visualizer. An example of a standalone application that implements SPARQL QBE (i(nteractive)SPARQL) is offered (see next).

2. iSPARQL

GPL

The OAT interactive SPARQL Query Builder is a SVG-based visual SPARQL query generator and results browser. It is also used in dbpedia. When working with the iSPARQL Query Builder, your entire interaction is centered around:
  1. Adding Nodes to the canvas.
  2. Connecting Nodes with Links.
  3. Typing the Nodes and the Links based on Concepts (Nodes) and Properties (Attributes and Relationships) exposed in the Schemas palette.
  4. Using connectors with broken lines to indicate Optional Links.
  5. Using the lasso effect to perform group selection for drag and drop on the query canvas, e.g., for the depiction of UNION queries.

OAT works in Gecko browsers (Firefox, Mozilla/SeaMonkey), IE6/7, Opera and Apple WebKit. (does it??)

Download iSPARQL here. (not sure though if this is the right version, not able to see "official download version). It seems that it is in OAT package.

I was not able to run an example following the the instructions here. But I managed to run queries here.

3. Freebase

CC

General info

Freebase is a large collaborative knowledge base consisting of metadata composed mainly by its community members. It is an online collection of structured data harvested from many sources, including individual 'wiki' contributions.[2] Freebase aims to create a global resource which allows people (and machines) to access common information more effectively. It was developed by the American software company Metaweb and has been running publicly since March 2007. Metaweb was acquired by Google in a private sale announced July 16, 2010.

Freebase is an open, Creative Commons licensed repository of structured data of almost 20 million entities.
An entity is a single person, place, or thing. Freebase connects entities together as a graph.
Ways to use Freebase:
  1. Use Freebase's Ids to uniquely identify entities anywhere on the web
  2. Query Freebase's data using MQL
  3. Build applications using our API or Acre, our hosted development platform.

Freebase has information about approximately 20 million Topics or Entities at the time of writing. Each one has a unique Id, which can help distinguish multiple entities which have similar names, such as Henry Ford the industrialist vs Henry Ford the footballer.

Most of our topics are associated with one or more types (such as people, places, books, films, etc) and may have additional properties like "date of birth" for a person or latitude and longitude for a location. These types and properties and related concepts are called Schema.

Anyone can contribute data to Freebase, and you can also build your own schema in a Base if Freebase does not yet have schema for a subject you're interested in.

List of datasources form which Freebase gets data.

All of Freebase's data (all entities and relationships in the graph (including full history), as well as blob data such as descriptions and images) are fully accessible through a REST API. API allows you to perform searches and queries against Freebase's data, or to write data to Freebase.

Freebase vs Linked Data: Freebase data are also available as RDF triples! See here and here.

Query editor

Freebase can be queried using MQL (Metaweb Query Language), which is a JSON-syntax query language. Not exactly SPARQL. The query editor can help you find topics, properties, and types wherever you need them inside your query.

4. Knoodl

Free but code is not availabe.

General info

Knoodl is a tool for creating, managing, and analyzing RDF/OWL descriptions. Its many features support collaboration in all stages of these activities. Knoodl is hosted in the Amazon EC2 cloud and can be used for free. Knoodl's key component is a semantic software architecture that supports Emergent Analytics. It is actually a semantic wiki.

Semantic technology offers a new paradigm for managing enterprise information assets. A semantic architecture creates a graph if all information. The graph represents entities and relationships between entities (facts). It can be distributed or centrally located. A graph-based approach frees data from being locked into a rigid schema. Everything exists as a URI (a node in a graph) with properties attached that define what the thing is. Any person or application anywhere can make an assertion about something simply by referencing its URI.
Different parts of the enterprise can create their own descriptions of information resources and other artifacts regarding their domain and as long as they use RDF and OWL to create the descriptions, their graph will naturally federate with the RDF descriptions created by other parts of the enterprise or with business partners.

Knoodl.com, is used to collaboratively construct, manage, and employ ontologies along with other information assets like relational databases or spreadsheets in a secure, scalable environment. Collaboration is important when developing ontologies because it enables organizations to reach a consensus on the meaning of things. A large enterprise or web-based community can take advantage of the network effect in building and evolving an ontology the same way that Wikipedia does. Individual people and applications may each add only a small number of assertions, but when these actions are performed on a large scale, as in an enterprise, new information begins to emerge. This is Emergent Analytics.

Query editor

See an overview.

Queries are saved as pages within a wiki or vocabulary, and can be referenced by wiki links just as any other wiki or vocabulary page. The initial view of a query contains wiki text and a parameter entry and submission form. Custom results formats can be designed with the view designer, and those views can be embedded within any wiki or vocabulary page. A query can be created either by creating and editing a query page, or by using the design manager. The query editor provides a visual workbench for query design and development.