rdf

One of the useful tool for visualization of RDF data is WebVOWL - http://visualdataweb.de/webvowl/. It supports RDF data in XML as well as in Turtle (TTL) formats and allows complex visualization of data.

Technology:

Apparently sparql doesn't allow non aggregate variables in the select clause unless they are also in the group by, which affects the query's meaning. So I came up with another solution which includes an intersection(join):

select ?country ?area ?lake
where {
?lake rdfs:label ?label .
?lake rdf:type dbo:Lake .
?lake dbo:areaTotal ?area .
?lake dbo:country ?country .
?country rdf:type dbo:Country .
FILTER (lang(?label) = 'en') .
FILTER(?maxarea = ?area)
{
select ?country (MAX(?area) AS ?maxarea)
where {
?lake rdfs:label ?label .
?lake rdf:type dbo:Lake .
?lake dbo:areaTotal ?area .
?lake dbo:country ?country .
?country rdf:type dbo:Country .
FILTER (lang(?label) = 'en') .
}
group by ?country
}
}

Technology:

Work with RDF - Solution Redland

The “Redland RDF Libraries” provide support for the Resource Description Framework (RDF). It provides basic functions as well as several bindings to different programming languages (for example: perl, python…). There are also packages for various Linux distributions and other operation systems available that make an installation quite easy (if all necessary additional libraries are already installed). However the Redland libraries provide the possibility to use BerkeleyDB or MYSQL as database storage as well as store the files temporary in the memory. These functions allow you to easily store, access, read or update your data via SPARQL (query language for RDF, similar to SQL) contained in the RDF files.

Taggings:

rdf resource declaration-solution

It is possible to define resource in one place and add properities in another like this:

<rdf:Description rdf:about="http://www.example.sk/Maria_Juana">
<rdf:type rdf:resource="http://xmlns.com/foaf/0.1/Person"/>
</rdf:Description>

<rdf:Description rdf:about="http://www.example.sk/Maria_Juana">
<rdf:name>Maria Juana</rdf:name>
</rdf:Description>

Taggings:

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