SPARQL Guide for the Visual Basic 6 (VB6) Developer
IntroductionThis is the Visual Basic 6 variation of Kingsley Idehen's SPARQL guides for PHP, Perl, Python, JavaScript developers and my guide forClassic ASP developers. I wanted to share this because quite a number of developers (including me) are still using Visual Basic 6 and It could also be used for Linked Data Application development. Visual Basic is on the top 20 most popular programming languages according to TIOBE Index as at december 2015
What?A simple guide usable by any Visual Basic 6 developer seeking to exploit SPARQL without hassles.
Why?SPARQL is a powerful query language, results serialization format, and an HTTP based data access protocol from the W3C. It provides a mechanism for accessing and integrating data across Deductive Database Systems (colloquially referred to as triple or quad stores in Semantic Web and Linked Data circles) -- database systems (or data spaces) that manage proposition oriented records in 3-tuple (triples) or 4-tuple (quads) form.
How?SPARQL queries are actually HTTP payloads (typically). Thus, using a RESTful client-server interaction pattern, you can dispatch calls to a SPARQL compliant data server and receive a payload for local processing e.g. local object binding re. Visual Basic 6 (vb6).
Steps:- Determine which SPARQL endpoint you want to access e.g. DBpedia or a local Virtuoso instance (typically: http://localhost:8890/sparql).
- If using Virtuoso, and you want to populate its quad store using SPARQL, assign "SPARQL_SPONGE" privileges to user "SPARQL" (this is basic control, more sophisticated WebID based ACLs are available for controlling SPARQL access).
- Make sure MSXML parser is installed on the server or you can download from here.
- Download VB-JSON: A Visual Basic 6 (VB6) JSON Parser Class Library.
- In Visual Basic, create a new Standard EXE project. Create and add a new module, "module1.bas".
- Add a project reference to Microsoft XML version 2.0, Microsoft scripting runtime, Microsoft ActiveX Data Objects library.
- Unzip the VB-JSON file. Extract the following files: "json.bas", "cJSONScript.cls" and "cStringBuilder.cls". Add them to the Visual Basic project
- Paste the following code in "module1.bas" file. See the inline comments for a description of how the code functions.
- Save and run the Visual Basic project.
Private m_SafeChar(0 To 255) As Boolean
Sub main()
Dim buf As New cStringBuilder
Dim p As Object
Dim result As String
Dim url As New cStringBuilder
Dim dsn As String
Dim parameters As String
Dim sparql As New cStringBuilder
On Error Resume Next
' Setting Data Source Name (DSN)
dsn = "http://dbpedia.org/sparql"
' HTTP URL is constructed accordingly with JSON query results format in mind.
parameters = "default-graph-uri=&should-sponge=&format=application%2Fsparql-results%2Bjson&timeout=0&debug=on"
' SPARQL Query
' List all the landlocked countries in Africa
sparql.Append "PREFIX rdfs: "
sparql.Append "PREFIX type:
Output:Retrieved Data Burkina Faso Ethiopia MalawiConclusion:
JSON was chosen over XML (re. output format) since this is about a "no-brainer installation and utilization" guide for a Javascript developer that already knows how to use Javascript for HTTP based data access within HTML. SPARQL just provides an added bonus to URL dexterity (delivered via URI abstraction) with regards to constructing Data Source Names or Addresses.
