Introduction

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Goals of RQL

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Comparison with existing languages

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

SQL

```

RQL may remind of SQL but works at a higher abstraction level (the *CubicWeb*

framework generates SQL from RQL to fetch data from relation databases). RQL is

focused on browsing relations. The user needs only to know about the *CubicWeb*

data model he is querying, but not about the underlying SQL model.

Sparql

``````

The query language most similar to RQL is SPARQL_, defined by the W3C to serve

for the semantic web.

Versa

`````

We should look in more detail, but here are already some ideas for the moment

... Versa_ is the language most similar to what we wanted to do, but the model

handling of the RDF types which does not interest us. On the functionality

level, Versa_ is very comprehensive including through many functions of

or another.  Finally, the syntax is a little esoteric.

The different types of queries

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Search (`Any`)

   Extract entities and attributes of entities.

Insert entities (`INSERT`)

   Insert new entities or relations in the database.

   It can also directly create relationships for the newly created entities.

Update entities, create relations (`SET`)

   Update existing entities in the database,

   or create relations between existing entities.

Delete entities or relationship (`DELETE`)

   Remove entities or relations existing in the database.

.. _Versa: http://uche.ogbuji.net/tech/rdf/versa/

.. _SPARQL: http://www.w3.org/TR/rdf-sparql-query/