Bio::DB::EUtilities::Cookie - simple object to hold NCBI cookie information and descriptions
Some EUtilities (epost,
esearch,
or elink) are able to retain information on the NCBI server under certain settings.
This information can be retrieved by using a cookie.
Here,
the idea of the 'cookie' is similar to the 'cookie' set on a user's computer when browsing the Web.
XML data returned by these EUtilities,
when applicable,
is parsed for the cookie information (the 'WebEnv' and 'query_key' tags to be specific) The information along with other identifying data,
such as the calling eutility,
description of query,
etc.) is stored as a Bio::DB::EUtilities::Cookie object in an internal queue.
These can be retrieved one at a time by using the next_cookie method or all at once in an array using get_all_cookies.
Each cookie can then be 'fed',
one at a time,
to another EUtility object,
thus enabling chained queries as demonstrated in the synopsis.
By default, a EUtilities object will retrieve records using a cookie if the cookie parameter is set. Also, the object will use the database parameter stored in the Bio::DB::EUtilities::Cookie object when the parameter isn't set upon instantiation:
my $efetch = Bio::DB::EUtilities->new(-cookie => $elink->next_cookie,
-rettype => 'fasta');
ELink, in particular, is capable of returning multiple cookies based on the setting for the database; if db is set to 'all', you will retrieve a cookie for each database with related records.
