1 

     2 Introduction

     3 ------------

     4 

     5 Goals of RQL

     6 ~~~~~~~~~~~~

     7 

     8 The goal is to have a language emphasizing the way of browsing

     9 relations. As such, attributes will be regarded as cases of

    10 special relations (in terms of implementation, the language

    11 user should see virtually no difference between an attribute and a

    12 relation).

    13 

    14 RQL is inspired by SQL but is the highest level. A knowledge of the 

    15 `CubicWeb` schema defining the application is necessary.

    16 

    17 Comparison with existing languages

    18 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

    19 

    20 SQL

    21 ```

    22 RQL builds on the features of SQL but is at a higher level

    23 (the current implementation of RQL generates SQL). For that it is limited

    24 to the way of browsing relations and introduces variables. 

    25 The user does not need to know the model underlying SQL, but the `CubicWeb` 

    26 schema defining the application.

    27 

    28 Versa

    29 `````

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

    31 the moment ... Versa_ is the language most similar to what we wanted

    32 to do, but the model underlying data being RDF, there is some

    33 number of things such as namespaces or handling of the RDF types which 

    34 does not interest us. On the functionality level, Versa_ is very comprehensive

    35 including through many functions of conversion and basic types manipulation,

    36 which may need to be guided at one time or another. 

    37 Finally, the syntax is a little esoteric.

    38 

    39 Sparql

    40 ``````

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

    42 for the semantic web. 

    43 

    44 

    45 The different types of queries

    46 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

    47 

    48 Search (`Any`)

    49    Extract entities and attributes of entities.

    50 

    51 Insert entities (`INSERT`)

    52    Insert new entities or relations in the database.

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

    54 

    55 Update entities, create relations (`SET`)

    56    Update existing entities in the database,

    57    or create relations between existing entities.

    58 

    59 Delete entities or relationship (`DELETE`)

    60    Remove entities or relations existing in the database.

    61 

    62    

    63 

    64 

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

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