CEQL is a simplified query language which gives access to all the most frequently-used features of CQP, but in a form that is much more accessible and friendly for beginners. For example, rather than using full regular expressions, simpler wildcard characters are used - such as a single star (*), rather than a dot-star (.*), meaning "any number of anything".
As such it is particularly suited to being implemented in web interfaces. Its most prominent use is in BNCweb, where by default all queries use CEQL rather than CQP syntax. Indeed, much of its design is modelled around the annotation of the BNC (POS tags, simplified POS tags, and lemmata).
In the BNCweb interface and documentation, CEQL is referred to as “Simple Query Syntax” in an effort to reduce acronym prevalence. It's exactly the same thing, though!
A more generalised and configurable version of CEQL is built into CQPweb. In CQPweb, the system administrator decides how the different aspects of the CEQL are linked-in to the underlying CWB corpus attributes.
Some other web interfaces with a CWB backend also allow queries to be expressed in CEQL.
The CEQL parser, which converts CEQL query strings into the corresponding CQP-syntax queries, is not part of the CWB core. Instead, it is part of the main CWB Perl module. Click here to find out how to install this software.
There are a number of different bits of documentation for CEQL. The most comprehensive is the discussion in Chapter 6 (pp. 93-117) of Hoffmann et al. (2008), Corpus Linguistics with BNCweb.
A shorter summary is built in to both BNCweb and CQPweb.
A longer guide for CQPweb system administrators, on how to configure the links between CEQL syntax and the underlying corpus structure, is also built in to CQPweb and available to view in its current version here. Note this file is somewhat out of date, though!
On a more technical level: when you have installed the CWB Perl module, the command
perldoc CWB::CEQL will open a manual page for
the CEQL parser. Or you can look at the code itself, from whence the Perldoc contents derive.
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