anchor.diff:    "Returns SNPs located in that interval."
     (let (query "select seq_region_id, seq_region_start, seq_region_end, seq_region_strand, variation_id, variation_name, consequence_type from variation_feature join homo_sapiens_core_47_36i.seq_region using (seq_region_id) where ....)
       ))
  +||#
  
positive.code: | validation_status | set('cluster','freq','submitter','doublehit','hapmap','failed') | YES  |     | NULL    |                |
  | ancestral_allele  | text                                                            | YES  |     | NULL    |                |
  +-------------------+-----------------------------------------------------------------+------+-----+---------+----------------+
  5 rows in set (0.04 sec)
  
  mysql> desc allele;
  +--------------+------------------+------+-----+---------+----------------+
  | Field        | Type             | Null | Key | Default | Extra          |
  +--------------+------------------+------+-----+---------+----------------+
  | allele_id    | int(10) unsigned |      | PRI | NULL    | auto_increment |
  | variation_id | int(10) unsigned |      | MUL | 0       |                |
  | allele       | varchar(255)     | YES  |     | NULL    |                |
  | frequency    | float            | YES  |     | NULL    |                |
  | sample_id    | int(10) unsigned | YES  |     | NULL    |                |
  +--------------+------------------+------+-----+---------+----------------+
  5 rows in set (0.04 sec)
  
  mysql> select * from variation limit 10;
  +--------------+-----------+------+------------------------+------------------+
  | variation_id | source_id | name | validation_status      | ancestral_allele |
  +--------------+-----------+------+------------------------+------------------+
  
negative.code: ;; This packages aims at characterising the link from genes to SNPs
  
  (in-package :clcb-ensembl)
  
  #||
   
  select * from source limit 10;
  +-----------+----------------------------------+---------+
  | source_id | name                             | version |
  +-----------+----------------------------------+---------+
  |         1 | dbSNP                            |     127 |
  |         3 | HGVbase                          |      15 |
  |         5 | TSC                              |       1 |
  |        11 | ENSEMBL:Watson                   |    NULL |
  |        10 | ENSEMBL:Venter                   |    NULL |
  |         9 | Affy GenomeWideSNP_6.0           |    NULL |
  |         8 | ENSEMBL:celera                   |    NULL |
  |         7 | Affy GeneChip 100K Mapping Array |    NULL |
  |         6 | Affy GeneChip 500K Mapping Array |    NULL |
  +-----------+----------------------------------+---------+
  
  ||#
  
  (def-view-class source ()
    ((source-id :db-type :key :type integer)
     (name :db-type base :type (string 255))
     (version :db-type base :type integer))
    (:base-table "source")
    (:documentation "This class answers how a particular variation was defined. A link from here to the variations with that same source ID is not feasible without extra constraints on the variations because of the large number that will be assigned to a single source."))
  
  #|| 				variation
  +-------------------+-----------------------------------------------------------------+------+-----+---------+----------------+
  | variation_id      | int(10) unsigned                                                |      | PRI | NULL    | auto_increment |
  | source_id         | int(10) unsigned                                                |      |     | 0       |                |
  