Learning SPARQL

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SPARQL Playground

Other platforms will have different arrangements. You'll need to download the ARC2 library; this downloads as a zip file, so you will need to unzip this and put the arc2-master folder in the same folder as the script. So the script folder will have the php file s and the arc2-master folder which in turn contain the support files and folders. You can simply copy and paste the code from the examples below.

Depending on the OS you are using, you may need to modify the permissions of the file in order to get it to run. Assuming all is well the results from the program will be presented in the browser window.

Querying and Updating with SPARQL 1.1

I'm going to illustrate this using a simple example. I built a small taxonomy project called Health, Exercise and Nutrition. The project has three concept schemes, covering the main topics of Health, Exercise and Food, but for this example, only the Nutrition concept scheme has been built out.

See the screenshot below, in which this concept scheme is selected. The top concepts are visible in the main panel pale blue background. The triplestore is the basis of all RDF applications, as the name implies each row contains a triple i. I found it easier to think in terms of resource, property name and property value. The resource and property names must be provided in the from of URIs unique resource identifiers the property value can be a URI or some normally typed entity such as a string or an integer.

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The triples describe a network of nodes the resource and property values with property names being the links between them, with this infrastructure any network can be described by a set of triples. Notice that the variable? This is a Basic Graph Pattern with three triple patterns. Now the size of the results has shrunk dramatically from the previous queries!

In fact, by asking for the additional information we are putting an implicit restriction on the query.


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  • Querying and Updating with SPARQL 1.1!

Cities that only have? But what if we want all cities to appear, regardless if they have a metro population? Either a triple exists or it does not. NULL values in relational databases are just a manifestation of the tabular logical data model; there needed to be some way to represent an empty cell. Basic graph pattern matching shown above enables you to select for data.

Learn SPARQL

You want data returned in a certain order, and usually only want to see a few results at a time. Together they enable you to pull down query results a page at a time. The results are returned in the order of their total populations so big cities like Houston would be the first results. The results are returned in the order of their total populations so big cities would be the top results.

With graph patterns and filters, SPARQL becomes a very powerful language for selecting only data that matches very specific criteria. The following filters are allowed:.

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Query 8 : This query is the same as query 7, but brings back the human readable name of each city with the results. This is a common occurrence in RDF. Unlike SQL, it is very easy to assign multiple values to a resource for a specific property. In this case, there is an rdfs:label for multiple languages in the dataset.


  1. SPARQL Tutorial?
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  3. Data Topics.
  4. Learning SPARQL, 2nd Edition by Bob DuCharme!
  5. The lang operator extracts the language tag of the value that is bound to? The langmatches operator matches the first language tag with the second language range.

    Conclusion

    Query 10 : This query shows how to use regular expression filters. The str operator extracts the string of the value that is bound to?

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