doc/book/en/C040-rql.en.txt
author Sandrine Ribeau <sandrine.ribeau@logilab.fr>
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.. -*- coding: utf-8 -*-
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.. _RQL:
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======================================
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RQL language (Relation Query Language)
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======================================
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Introduction
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============
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Goals RQL
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---------
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The goal is to have a language emphasizing the way of browsing
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relations. As such, attributes will be regarded as cases of
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special relations (in terms of implementation, the user
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language not to see virtually no difference between an attribute and a
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relation).
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RQL is inspired by SQL but is the highest level. A knowledge of the 
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`CubicWeb` schema defining the application is necessary.
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Comparison with existing languages
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----------------------------------
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SQL
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```
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RQL builds on the features of SQL but is at a higher level
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(the current implementation of RQL generates SQL). For that it is limited
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to the way of browsing relations and introduces variables. 
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The user does not need to know the model underlying SQL, but the `CubicWeb` 
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scheam defining the application.
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Versa
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`````
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Should I look in more detail, but here is already some ideas for
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the moment ... Versa_ is the language most similar to what we wanted
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to do, but the model underlying data being RDF, there is some
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number of things such as namespaces or handling of the RDF types which 
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does not interest us. On the functionality level, Versa_ is very comprehensive
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including through many functions of conversion and basic types manipulation,
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which may need to be guided at one time or another. 
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Finally, the syntax is a little esoteric.
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Sparql
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``````
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The query language most similar to RQL is SPARQL_, defined by the W3C to serve
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for the semantic web. 
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The different types of queries
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------------------------------
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Search (`Any`)
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   This type of query can extract entities and attributes of entities.
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Inserting entities (`INSERT`)
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   This type of query is used to insert new entities in the database. It
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   will also create direct relationships entities newly created.
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Update entities, relations creation (`SET`)
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   This type of query updates existing entities in the database,
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   or create relations between existing entities.
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Deletion of entities or relationship (`DELETE`)
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   This type of query allows for the removal of entities and relations existing
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   in the database.
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Search Query
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------------
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   [ `DISTINCT`] <entity type> V1 (V2) \ *
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   [ `GROUPBY` V1 (V2) \*] [ `ORDERBY` <orderterms>]
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   [ `WHERE` <restriction>]
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   [ `LIMIT` <value>] [ `OFFSET` <value>]
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:entity type:
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   Type of selected variables.
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   The special type `Any` is equivalent to not specify a type.
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:restriction:
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   list of relations to go through whic follow the pattern
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     `V1 relation V2 | <static value>`
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:orderterms:
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   Definition of the selection order: variable or column number followed by
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   sorting method ( `ASC`, `DESC`), ASC is the default.
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:note for grouped queries:
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   For grouped queries (e.g., a clause `GROUPBY`), all
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   selected variables must be aggregated or grouped.
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- *Search for the object of identifier 53*
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   ::
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        Any WHERE X
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        X eid 53
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- *Search material such as comics, owned by syt and available*
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   ::
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        WHERE X Document
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        X occurence_of F, F class C, C name 'Comics'
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        X owned_by U, U login 'syt'
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        X available true
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- *Looking for people working for eurocopter interested in training*
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   ::
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        Person P WHERE
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        P work_for P, S name 'Eurocopter'
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        P interested_by T, T name 'training'
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- *Search note less than 10 days old written by jphc or ocy*
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   ::
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        Note N WHERE
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        N written_on D, D day> (today -10),
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        N written_by P, P name 'jphc' or P name 'ocy'
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- *Looking for people interested in training or living in Paris*
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   ::
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        Person P WHERE
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        (P interested_by T, T name 'training') or
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        (P city 'Paris')
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- *The name and surname of all people*
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   ::
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        Any N, P WHERE
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        X is Person, X name N, X first_name P
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209
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   Note that the selection of several entities generally force
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   the use of "Any" because the type specification applies otherwise
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   to all the selected variables. We could write here
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   ::
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        String N, P WHERE
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        X is Person, X name N, X first_name P
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209
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Insertion query
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---------------
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    `INSERT` <entity type> V1 (, <entity type> V2) \ * `:` <assignments>
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    [ `WHERE` <restriction>]
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: assignments:
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   list of relations to assign in the form `V1 relationship V2 | <static value>`
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The restriction can define variables used in assignments.
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Caution, if a restriction is specified, the insertion is done for 
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*each line results returned by the restriction*.
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- *Insert a new person named 'foo'*
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   ::
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        INSERT Person X: X name 'widget'
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- *Insert a new person named 'foo', another called 'nice' and a 'friend' relation
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  between them*
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  ::
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        INSERT Person X, Person Y: X name 'foo', Y name 'nice', X friend Y
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- *Insert a new person named 'foo' and a 'friend' relation with an existing 
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  person called 'nice'*
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  ::
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        INSERT Person X: X name 'foo', X friend  Y WHERE name 'nice'
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209
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Update and relation creation queries
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------------------------------------
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    `SET` <assignements>
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    [ `WHERE` <restriction>]
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Caution, if a restriction is specified, the update is done *for
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each line results returned by the restriction*.
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- *Renaming of the person named 'foo' to 'bar' with the first name changed*
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  ::
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        SET X name 'bar', X first_name 'original' where X is Person X name 'foo'
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- *Insert a relation of type 'know' between objects linked by 
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  the relation of type 'friend'*
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  ::
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        SET X know Y  WHERE X friend Y
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209
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Deletion query
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--------------
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    `DELETE` (<entity type> V) | (V1 relation v2 ),...
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    [ `WHERE` <restriction>]
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Caution, if a restriction is specified, the deletion is made *for
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each line results returned by the restriction*.
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209
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- *Deletion of the person named 'foo'*
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  ::
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        DELETE Person X WHERE X name 'foo'
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- *Removal of all relations of type 'friend' from the person named 'foo'*
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  ::
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        DELETE X friend Y WHERE X is Person, X name 'foo'
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93
9c919a47e140 [doc] total file reorganisation - phase 1 complete
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parents:
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209
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Language definition
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===================
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Reserved keywords
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-----------------
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The keywords are not case sensitive.
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::
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     DISTINCT, INSERT, SET, DELETE,
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     WHERE, AND, OR, NOT
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     IN, LIKE,
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     TRUE, FALSE, NULL, TODAY, NOW
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     GROUPBY, ORDERBY, ASC, DESC
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Variables and Typing
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--------------------
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With RQL, we do not distinguish between entities and attributes. The
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value of an attribute is considered an entity of a particular type (see
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below), linked to one (real) entity by a relation called the name of
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the attribute.
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Entities and values to browse and/or select are represented in
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the query by *variables* that must be written in capital letters.
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There is a special type **Any**, referring to a non specific type.
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We can restrict the possible types for a variable using the
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special relation **is**.
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The possible type(s) for each variable is derived from the schema
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according to the constraints expressed above and thanks to the relations between
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each variable.
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Built-in types
209
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``````````````
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The base types supported are string (between double or single quotes),
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integers or floats (the separator is the'.'), dates and
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boolean. We expect to receive a schema in which types String,
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Int, Float, Date and Boolean are defined.
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* `String` (literal: between double or single quotes).
209
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* `Int`, `Float` (separator being'.').
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* `Date`, `Datetime`, `Time` (literal: string YYYY/MM/DD [hh:mm] or keywords
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   `TODAY` and `NOW`).
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* `Boolean` (keywords `TRUE` and `FALSE`).
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* `Keyword` NULL.
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Operators
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---------
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Logical Operators
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```````````````````
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::
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209
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     AND, OR, ','
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',' is equivalent to 'AND' but with the smallest among the priority
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of logical operators (see :ref:`PriorityOperators`).
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Mathematical Operators
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``````````````````````
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::
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209
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     +, -, *, /
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Comparison operators
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````````````````````
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::
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     =, <, <=, >=, > = ~, IN, LIKE
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209
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* The operator `=` is the default operator.
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209
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* The operator `LIKE` equivalent to `~=` can be used with the
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  special character `%` in a string to indicate that the chain 
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  must start or finish by a prefix/suffix:
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  ::
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209
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     Any X WHERE X name =~ 'Th%'
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     Any X WHERE X name LIKE '%lt'
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209
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* The operator `IN` provides a list of possible values:
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  ::
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    Any X WHERE X name IN ( 'chauvat', 'fayolle', 'di mascio', 'thenault')
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XXX nico: A trick <> 'bar' would not it be more convenient than NOT A
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trick 'bar'?
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.. _PriorityOperators:
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Operators priority
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``````````````````
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1. '*', '/'
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2. '+', '-'
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209
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3. 'and'
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4. 'or'
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5. ','
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209
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Advanced Features
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-----------------
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Functions aggregates
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````````````````````
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::
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     COUNT, MIN, MAX, AVG, SUM
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Functions on string
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```````````````````
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::
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209
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     UPPER, LOWER
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Optional relations
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``````````````````
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* They allow you to select entities related or not to another.
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* You must use the `?` behind the variable to specify that the relation
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  toward it is optional:
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   - Anomalies of a project attached or not to a version ::
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       Any X, V WHERE X concerns P, P eid 42, X corrected_in V?
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   - All cards and the project they document if necessary ::
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       Any C, P WHERE C is Card, P? documented_by C
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BNF grammar
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-----------
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The terminal elements are in capital letters, non-terminal in lowercase.
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The value of the terminal elements (between quotes) is a Python regular
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expression.
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::
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     statement:: = (select | delete | insert | update) ';'
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     # select specific rules
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     select      ::= 'DISTINCT'? E_TYPE selected_terms restriction? group? sort?
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     selected_terms ::= expression ( ',' expression)*
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     group       ::= 'GROUPBY' VARIABLE ( ',' VARIABLE)*
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     sort        ::= 'ORDERBY' sort_term ( ',' sort_term)*
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     sort_term   ::=  VARIABLE sort_method =?
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     sort_method ::= 'ASC' | 'DESC'
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     # delete specific rules
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     delete ::= 'DELETE' (variables_declaration | relations_declaration) restriction?
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     # insert specific rules
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     insert ::= 'INSERT' variables_declaration ( ':' relations_declaration)? restriction?
93
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209
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     # update specific rules
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     update ::= 'SET' relations_declaration restriction
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parents: 127
diff changeset
   394
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   395
     # common rules
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   396
     variables_declaration ::= E_TYPE VARIABLE (',' E_TYPE VARIABLE)*
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   397
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   398
     relations_declaration ::= simple_relation (',' simple_relation)*
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   399
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   400
     simple_relation ::= VARIABLE R_TYPE expression
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   401
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   402
     restriction ::= 'WHERE' relations
115
4b66ad23fbd1 [doc] merge old lax book with the rest
Nicolas Chauvat <nicolas.chauvat@logilab.fr>
parents: 113
diff changeset
   403
209
38a9c240ac64 [doc] Now uses specs from rql/doc
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parents: 127
diff changeset
   404
     relations   ::= relation (LOGIC_OP relation)*
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   405
                   | '(' relations')'
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   406
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   407
     relation    ::= 'NOT'? VARIABLE R_TYPE COMP_OP? expression
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   408
                   | 'NOT'? R_TYPE VARIABLE 'IN' '(' expression (',' expression)* ')'
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   409
                   
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   410
     expression  ::= var_or_func_or_const (MATH_OP var_or_func_or_const) *
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   411
                   | '(' expression ')'
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   412
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   413
     var_or_func_or_const ::= VARIABLE | function | constant
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   414
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   415
     function    ::= FUNCTION '(' expression ( ',' expression) * ')'
38a9c240ac64 [doc] Now uses specs from rql/doc
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parents: 127
diff changeset
   416
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   417
     constant    ::= KEYWORD | STRING | FLOAT | INT
115
4b66ad23fbd1 [doc] merge old lax book with the rest
Nicolas Chauvat <nicolas.chauvat@logilab.fr>
parents: 113
diff changeset
   418
209
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   419
     # tokens
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   420
     LOGIC_OP ::= ',' | 'GOLD' | 'AND'
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   421
     MATH_OP  ::= '+' | '-' | '/' | '*'
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   422
     COMP_OP  ::= '>' | '>=' | '=' | '<=' | '<' | '~=' | 'LIKE'
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   423
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   424
     FUNCTION ::= 'MIN' | 'MAX' | 'SUM' | 'AVG' | 'COUNT' | 'upper' | 'LOWER'
115
4b66ad23fbd1 [doc] merge old lax book with the rest
Nicolas Chauvat <nicolas.chauvat@logilab.fr>
parents: 113
diff changeset
   425
209
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   426
     VARIABLE ::= '[A-Z][A-Z0-9]*'
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   427
     E_TYPE   ::= '[A-Z]\w*'
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   428
     R_TYPE   ::= '[a-z_]+'
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   429
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   430
     KEYWORD  ::= 'TRUE' | 'FALSE' | 'NULL' | 'TODAY' | 'NOW'
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   431
     STRING   ::= "'([^'\]|\\.)*'" |'"([^\"]|\\.)*\"'
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   432
     FLOAT    ::= '\d+\.\d*'
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   433
     INT      ::= '\d+'
115
4b66ad23fbd1 [doc] merge old lax book with the rest
Nicolas Chauvat <nicolas.chauvat@logilab.fr>
parents: 113
diff changeset
   434
209
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   435
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   436
Remarks
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   437
-------
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   438
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   439
Sorting and groups
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   440
``````````````````
115
4b66ad23fbd1 [doc] merge old lax book with the rest
Nicolas Chauvat <nicolas.chauvat@logilab.fr>
parents: 113
diff changeset
   441
209
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   442
- For grouped queries (e.g. with a GROUPBY clause), all
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   443
  selected variables should be grouped.
115
4b66ad23fbd1 [doc] merge old lax book with the rest
Nicolas Chauvat <nicolas.chauvat@logilab.fr>
parents: 113
diff changeset
   444
209
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   445
- To group and/or sort by attributes, we can do: "X,L user U, U
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   446
  login L GROUPBY L, X ORDERBY L"
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   447
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   448
- If the sorting method (SORT_METHOD) is not specified, then the sorting is
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   449
  ascendant.
115
4b66ad23fbd1 [doc] merge old lax book with the rest
Nicolas Chauvat <nicolas.chauvat@logilab.fr>
parents: 113
diff changeset
   450
4b66ad23fbd1 [doc] merge old lax book with the rest
Nicolas Chauvat <nicolas.chauvat@logilab.fr>
parents: 113
diff changeset
   451
Negation
209
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   452
````````
115
4b66ad23fbd1 [doc] merge old lax book with the rest
Nicolas Chauvat <nicolas.chauvat@logilab.fr>
parents: 113
diff changeset
   453
209
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   454
* A query such as `Document X WHERE NOT X owned_by U` means "the
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   455
  documents have no relation `owned_by`".
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   456
* But the query `Document X WHERE NOT X owned_by U, U login "syt"`
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   457
  means "the documents have no relation `owned_by` with the user
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   458
  syt". They may have a relation "owned_by" with another user.
115
4b66ad23fbd1 [doc] merge old lax book with the rest
Nicolas Chauvat <nicolas.chauvat@logilab.fr>
parents: 113
diff changeset
   459
4b66ad23fbd1 [doc] merge old lax book with the rest
Nicolas Chauvat <nicolas.chauvat@logilab.fr>
parents: 113
diff changeset
   460
Identity
209
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   461
````````
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   462
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   463
You can use the special relation `identity` in a query to 
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   464
add an identity constraint between two variables. This is equivalent
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   465
to ``is`` in python::
115
4b66ad23fbd1 [doc] merge old lax book with the rest
Nicolas Chauvat <nicolas.chauvat@logilab.fr>
parents: 113
diff changeset
   466
209
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   467
   Any A WHERE A comments B, A identity B
115
4b66ad23fbd1 [doc] merge old lax book with the rest
Nicolas Chauvat <nicolas.chauvat@logilab.fr>
parents: 113
diff changeset
   468
209
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   469
return all objects that comment themselves. The relation
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   470
`identity` is especially useful when defining the rules for securities
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   471
with `RQLExpressions`.
115
4b66ad23fbd1 [doc] merge old lax book with the rest
Nicolas Chauvat <nicolas.chauvat@logilab.fr>
parents: 113
diff changeset
   472
209
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   473
Implementation
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   474
==============
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   475
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   476
Internal representation (syntactic tree)
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   477
----------------------------------------
115
4b66ad23fbd1 [doc] merge old lax book with the rest
Nicolas Chauvat <nicolas.chauvat@logilab.fr>
parents: 113
diff changeset
   478
209
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   479
The tree research does not contain the selected variables 
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   480
(e.g. there is only what follows "WHERE").
115
4b66ad23fbd1 [doc] merge old lax book with the rest
Nicolas Chauvat <nicolas.chauvat@logilab.fr>
parents: 113
diff changeset
   481
209
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   482
The insertion tree does not contain the variables inserted or relations
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   483
defined on these variables (e.g. there is only what follows "WHERE").
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   484
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   485
The removal tree does not contain the deleted variables and relations
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   486
(e.g. there is only what follows the "WHERE").
115
4b66ad23fbd1 [doc] merge old lax book with the rest
Nicolas Chauvat <nicolas.chauvat@logilab.fr>
parents: 113
diff changeset
   487
209
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   488
The update tree does not contain the variables and relations updated
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   489
(e.g. there is only what follows the "WHERE").
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   490
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   491
::
93
9c919a47e140 [doc] total file reorganisation - phase 1 complete
Nicolas Chauvat <nicolas.chauvat@logilab.fr>
parents:
diff changeset
   492
209
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   493
     Select         ((Relationship | And | Gold)?, Group?, Sort?)
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   494
     Insert         (Relations | And | Gold)?
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   495
     Delete         (Relationship | And | Gold)?
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   496
     Update         (Relations | And | Gold)?
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   497
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   498
     And            ((Relationship | And | Gold), (Relationship | And | Gold))
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   499
     Or             ((Relationship | And | Gold), (Relationship | And | Gold))
115
4b66ad23fbd1 [doc] merge old lax book with the rest
Nicolas Chauvat <nicolas.chauvat@logilab.fr>
parents: 113
diff changeset
   500
209
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   501
     Relationship   ((VariableRef, Comparison))
115
4b66ad23fbd1 [doc] merge old lax book with the rest
Nicolas Chauvat <nicolas.chauvat@logilab.fr>
parents: 113
diff changeset
   502
209
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   503
     Comparison     ((Function | MathExpression | Keyword | Constant | VariableRef) +)
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   504
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   505
     Function       (())
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   506
     MathExpression ((MathExpression | Keyword | Constant | VariableRef), (MathExpression | Keyword | Constant | VariableRef))
115
4b66ad23fbd1 [doc] merge old lax book with the rest
Nicolas Chauvat <nicolas.chauvat@logilab.fr>
parents: 113
diff changeset
   507
209
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   508
     Group          (VariableRef +)
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   509
     Sort           (SortTerm +)
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   510
     SortTerm       (VariableRef +)
115
4b66ad23fbd1 [doc] merge old lax book with the rest
Nicolas Chauvat <nicolas.chauvat@logilab.fr>
parents: 113
diff changeset
   511
209
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   512
     VariableRef    ()
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   513
     Variable       ()
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   514
     Keyword        ()
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   515
     Constant       ()
115
4b66ad23fbd1 [doc] merge old lax book with the rest
Nicolas Chauvat <nicolas.chauvat@logilab.fr>
parents: 113
diff changeset
   516
4b66ad23fbd1 [doc] merge old lax book with the rest
Nicolas Chauvat <nicolas.chauvat@logilab.fr>
parents: 113
diff changeset
   517
209
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   518
Remarks
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   519
-------
115
4b66ad23fbd1 [doc] merge old lax book with the rest
Nicolas Chauvat <nicolas.chauvat@logilab.fr>
parents: 113
diff changeset
   520
209
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
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diff changeset
   521
- The current implementation does not support linking two relations of type
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   522
  'is' with a OR. I do not think that the negation is  supported on this type 
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   523
  of relation (XXX FIXME to be confirmed).
115
4b66ad23fbd1 [doc] merge old lax book with the rest
Nicolas Chauvat <nicolas.chauvat@logilab.fr>
parents: 113
diff changeset
   524
209
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   525
- Relations defining the variables must be left to those using them. 
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   526
  For example::
115
4b66ad23fbd1 [doc] merge old lax book with the rest
Nicolas Chauvat <nicolas.chauvat@logilab.fr>
parents: 113
diff changeset
   527
209
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   528
     Point P where P abs X, P ord Y, P value X+Y
115
4b66ad23fbd1 [doc] merge old lax book with the rest
Nicolas Chauvat <nicolas.chauvat@logilab.fr>
parents: 113
diff changeset
   529
209
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   530
   is valid, but::
115
4b66ad23fbd1 [doc] merge old lax book with the rest
Nicolas Chauvat <nicolas.chauvat@logilab.fr>
parents: 113
diff changeset
   531
209
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   532
     Point P where P abs X, P value X+Y, P ord Y
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   533
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   534
   is not.
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   535
115
4b66ad23fbd1 [doc] merge old lax book with the rest
Nicolas Chauvat <nicolas.chauvat@logilab.fr>
parents: 113
diff changeset
   536
4b66ad23fbd1 [doc] merge old lax book with the rest
Nicolas Chauvat <nicolas.chauvat@logilab.fr>
parents: 113
diff changeset
   537
209
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   538
Conclusion
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   539
==========
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   540
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   541
Limitations
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   542
-----------
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   543
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   544
It lacks at the moment:
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   545
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   546
- COALESCE
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   547
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   548
- restrictions on groups (HAVING)
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   549
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   550
and certainly other things ...
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   551
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   552
A disadvantage is that to use this language we must know the
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   553
format used (with real relation names and entities, not those viewing
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   554
in the user interface). On the other hand, we can not really bypass
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   555
that, and it is the job of a user interface to hide the RQL.
115
4b66ad23fbd1 [doc] merge old lax book with the rest
Nicolas Chauvat <nicolas.chauvat@logilab.fr>
parents: 113
diff changeset
   556
4b66ad23fbd1 [doc] merge old lax book with the rest
Nicolas Chauvat <nicolas.chauvat@logilab.fr>
parents: 113
diff changeset
   557
209
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   558
Topics
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   559
------
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   560
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   561
It would be convenient to express the schema matching
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   562
relations (non-recursive rules)::
115
4b66ad23fbd1 [doc] merge old lax book with the rest
Nicolas Chauvat <nicolas.chauvat@logilab.fr>
parents: 113
diff changeset
   563
209
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   564
     Document class Type <-> Document occurence_of Fiche class Type
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   565
     Sheet class Type    <-> Form collection Collection class Type
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   566
    
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   567
Therefore 1. becomes::
115
4b66ad23fbd1 [doc] merge old lax book with the rest
Nicolas Chauvat <nicolas.chauvat@logilab.fr>
parents: 113
diff changeset
   568
209
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   569
     Document X where
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   570
     X class C, C name 'Cartoon'
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   571
     X owned_by U, U login 'syt'
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   572
     X available true
115
4b66ad23fbd1 [doc] merge old lax book with the rest
Nicolas Chauvat <nicolas.chauvat@logilab.fr>
parents: 113
diff changeset
   573
209
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   574
I'm not sure that we should handle this at RQL level ...
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   575
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   576
There should also be a special relation 'anonymous'.
115
4b66ad23fbd1 [doc] merge old lax book with the rest
Nicolas Chauvat <nicolas.chauvat@logilab.fr>
parents: 113
diff changeset
   577
4b66ad23fbd1 [doc] merge old lax book with the rest
Nicolas Chauvat <nicolas.chauvat@logilab.fr>
parents: 113
diff changeset
   578
209
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   579
274
893353d66f86 [doc] fix rql intro
Nicolas Chauvat <nicolas.chauvat@logilab.fr>
parents: 255
diff changeset
   580
.. _Versa: http://uche.ogbuji.net/tech/rdf/versa/
893353d66f86 [doc] fix rql intro
Nicolas Chauvat <nicolas.chauvat@logilab.fr>
parents: 255
diff changeset
   581
.. _SPARQL: http://www.w3.org/TR/rdf-sparql-query/
209
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   582
38a9c240ac64 [doc] Now uses specs from rql/doc
Sandrine Ribeau <sandrine.ribeau@logilab.fr>
parents: 127
diff changeset
   583
274
893353d66f86 [doc] fix rql intro
Nicolas Chauvat <nicolas.chauvat@logilab.fr>
parents: 255
diff changeset
   584
[FIXME] see also RQL documentation in source rql/doc.