Scheduled for v1.1
BioSQL v1.1 may have changes that may not be fully backwards compatible, such as new or dropped tables, or changes in the cardinality of relationships. At a minimum it will require language bindings to be extensively tested for compatibility with the changes.
It would be desirable to have a flag to indicate a circular sequence in the BioSequence table.
Surrogate primary keys on all tables
The current BioSQL unique keys enforce constraints upon the data. Most have primary keys in addition but in some tables there is no primary key. Here it is implied that the unique key is the primary key, but using compound keys such as this is not 'tidy' (because some columns in the key may be mutable, whereas normally a primary key is assumed to be immutable by most generic ORMs) and causes problems when attempting to auto-generate code using tools such as Java's recent JPA system.
The proposal is to have a separate surrogate primary key on such tables, just as one would if that table were being referenced elsewhere in the db schema (even though in this case it isn't).
This should fit nicely with general relational db design - unique key (in MySQL, for example) is just a type of constraint over the data, whereas in general primary keys are a method of uniquely identifying an individual row. Primary keys are a subset of unique keys but they should not be used to enforce data business rules.
Synonym is a reserved word in some RDBMSs
The column synonym in table term_synonym is a reserved word in at least Oracle. Rename the column synonym to name, which would also be more consistent with column naming in other tables (as the fact that it is a synonym is already in the table name).
Term_Relationship_Term can be folded into Term_Relationship
The Term_Relationship_Term table links a relationship between two terms to a first-class term that is equivalent to the relationship (reification). As this is a 1-1 relationship, it should be folded into the Term_Relationshop column (as a foreign key).
The Oracle version demonstrates that this can actually be fully mapped back to a Term_Relationship_Term view (for backwards compatibility, for example), using triggers (or RULEs for PostgreSQL) to make it fully writable.
Comment is a reserved word in some RDBMSs
There is a table named 'comment' (for holding comment-type annotation), which is a reserved in some RDBMSs, for example HSQLDB and Oracle.
The proposal is to rename the table to 'anncomment'. For the sake of consistency, this would also mean to rename the primary key of the table to anncomment_id.
BioSQL reference table cannot store more than one db_xref. This causes an inadequacy in parsing Uniprot where references often contain Pubmed id, Medline id and DOI.
References may also have additional attributes (remarks, GeneRIFs, etc), and thus one needs a Reference_Qualifier_Value table to store those. Furthermore, it would be good to be able to store the type of a reference (eg. journal, book, article, conference paper, etc.).
Check constraint on biosequence.alphabet
The Bio* toolkits turn out to use slight variations of the set of valid alphabet names. Consistency could be enforced through a check constraint.
BioPerl uses protein, dna, and rna. Biojava reportedly uses all-uppercase for all three.
Scheduled for v1.0.x
All BioSQL v.1.0.x schemas at a minimum can be expected to work with all language bindings and software that ran with a recent, but pre-release schema (the so-called 'post-Singapore' schema). As such, there will be no changes in tables, table names, column names, or relationship cardinalities. Except if necessitated to fix a serious bug, column type changes will be limited to changing the width (or precision) of columns.
Other allowable changes include additional indexes, or changing the column order in existing compound indexes to increase performance. Unique key changes do not, however, fall into this category, as language bindings may frequently rely on them for uniquely locating records.
Need additional attributes for taxon
The NCBI taxonomy has a isTaxonHidden attribute determining whether a taxon is included in the lineage information given in GenBank entries:
GenBank hidden flag (1 or 0) -- 1 if name is suppressed in GenBank entry lineage
On hand at this point this applies only to the NCBI taxonomy and not to any other, but also the other attributes of the taxon table are pretty specific to the NCBI taxonomy, so we might as well add this one. In addition, one might in fact want to search by it (for instance, for pulling out all ancestors of a given taxon that are visible). (See the respective thread on the BioSQL mailing list for reference.)
Alternatively, we could generalize the taxon model to be as applicable to other taxonomies, and move special attributes to a taxon_qualifier_value table.
Bioentry Date Stamping
Possible table structure:
CREATE TABLE bioentry_history ( bioentry_history_id INT UNSIGNED NOT NULL AUTO_INCREMENT, bioentry_id INT UNSIGNED NOT NULL FOREIGN KEY REFERENCES (bioentry.bioentry.id) startdate DATE NOT NULL DEFAULT CURRENT_DATE, enddate DATE NULL );
Example SQL - give me all the entries from GenBank as they existed on Jan 1, 2002
SELECT bioentry.* FROM bioentry JOIN biodatabase USING (biodatabase_id) JOIN bioentry_history USING (bioentry_id) WHERE biodatabase.name = 'GenBank' AND bioentry_history.startdate <= 2002-01-01 AND (bioentry_history.enddate IS NULL OR bioentry_history.enddate > 2002-01-01)
Alternative, if you want db history info as well:
CREATE TABLE biodatabase_history ( biodatabase_history_id INT UNSIGNED NOT NULL AUTO_INCREMENT, biodatabase_id INT UNSIGNED NOT NULL FOREIGN KEY REFERENCES (biodatabase.biodatabase_id) entrydate DATE NOT NULL DEFAULT CURRENT_DATE -- date db was updated comment TEXT -- optional; maybe you want versioning here, I dunno ); CREATE TABLE bioentry_history ( bioentry_history_id INT UNSIGNED NOT NULL AUTO_INCREMENT, bioentry_id INT UNSIGNED NOT NULL FOREIGN KEY REFERENCES (bioentry.bioentry_id) entered INT UNSIGNED NOT NULL FOREIGN KEY REFERENCES (biodatabase_history.biodatabase_history_id) removed INT UNSIGNED NULL FOREIGN KEY REFERENCES (biodatabase_history.biodatabase_history_id) ); ALTER TABLE bioentry_history ADD CONSTRAINT check_entered_removed ( bioentry_history.removed IS NULL OR bioentry_history.entered <> bioentry_history.removed );
Example SQL - same as before, retrieve all bioentries from GenBank as they were on Jan 1, 2002
SELECT bioentry.* FROM bioentry JOIN biodatabase USING (biodatabase_id) JOIN bioentry_history USING (bioentry_id) LEFT JOIN biodatabase_history AS enter ON (bioentry_history.entered = entered.bioentry_history_id) LEFT JOIN biodatabase_history AS exit ON (bioentry_history.removed = exit.bioentry_history_id) WHERE biodatabase.name = 'GenBank' AND entered.entrydate <= 2002-01-01 AND (exit.entrydate IS NULL OR exit.entrydate > 2002-01-01)
Advantage: you don't need to store N*M rows for every M database updates, only N rows of date ranges (or database version refs).
Disadvantage: all historical bioentries remain in the database, even ones that are no longer "current" - simple SELECTs must specify enddate IS NULL (optionally, a "is_current" flag can be added to bioentry) - again, a bioentry_current VIEW may be the best solution.
There is no utility here for handling biosequence redundancy; i.e. the biosequence table cannot be easily used to generate non-redundant sequence views. An accessory table "biosequence_redundancy" could be used to store redundant pairs (including a self-self pair) for those who need it.
CREATE TABLE biosequence_redundancy ( biosequence_redundancy_id INT UNSIGNED NOT NULL AUTO_INCREMENT, biosequence_a INT UNSIGNED NOT NULL FOREIGN KEY REFERENCES (biosequence.biosequence_id), biosequence_b INT UNSIGNED NOT NULL FOREIGN KEY REFERENCES (biosequence.biosequence_id), UNIQUE(biosequence_a, biosequence_b) );
This redundancy table could be further "typed" by ontology terms. Alternatively, all redundancies could be stored as pairwise seqfeatures.
Example SQL: Give me all nonredundant biosequences from GenPept (i.e. the NCBI "nr" database)
Nasty cross-joining SQL to be delivered ...
Feature set versioning
Could already be accomplished with "dated" source ontology terms, but that seems like a bastardization. Suggestions welcome.
Ability to fully represent contig assembly
The ability to fully represent EMBL format's CO lines in a BioSQL record would be desirable. The CO line is essentially a join of segments of other sequences, like this:
This describes the sequence as being constructed of the first 40 bases of MySeq, followed by bases 5 to 8 of ThisSeq, followed by a gap of unknown length, followed by bases 90-154 of ThatSeq, followed by a gap of length 4000, followed by bases 100-2000 of TheirSeq. All entries in the join statement are immediately adjacent, but owing to the use of gaps of unknown length it is not possible to map components that occur after that gap to a specific location in the assembled contig sequence.
The 'unk100' keyword used to represent the unknown length gap as the keyword specified by the EMBL format docs, but it does not explain why this keyword is used or what it means, or how it affects the overall computation of the sequence length.
This join statement takes the place of any actual sequence data associated with the EMBL entry. The length of the sequence the join represents is computed by an unknown function using the above join statement as input.
The approach to store this in BioSQL would be via features on the contig (a bioentry) which have remote locations.
However, the gaps do not have a remote location, and they do not have a direct location on the contig either (if the first one had a known length, the locations could be inferred). While BioSQL itself does permit location-less features, some of the Bio* toolkits may have difficulty dealing with this. The only way to represent that the first gap feature has unknown length is through its annotation (seqfeature_qualifier_value).
While the second gap has a known length, BioSQL (and, for example, neither BioPerl) can't represent the length of a feature other than by its coordinates (which aren't known in the example above, due to the preceding gap of unknown length). One could work around that by giving the second gap a remote location to a fictitious 'gap' sequence (which would only consist of gap characters, and be virtual).
Should there be a better way of doing this?
Related to CO lines, EMBLs AS lines store assembly path information. In essence, these could be stored as feature pairs, one feature on the source contig (or read, another bioentry), the other feature on the assembled contig (the entry with the AS line), and both linked by seqfeature_relationship. The complicating factor is that the location of the source contig feature may not be known, resulting in a location-less feature. This should be fine from BioSQL's standpoint, but may cause trouble when processed with on of the Bio* toolkits.
Support for chimeric sequences
BioSQL only allows a single taxon link for a species. This creates a difficulty for representing chimeric sequences. See a BioSQL-l thread in March 2008 discussing an example.
It should be noted that currently probably none of the Bio* toolkits supports multiple species for sequences either, so there isn't a need (or possible use) for that capability in BioSQL from that side. There are plans to change this, though.
Abstracts and Full Text on References
As an enhancement for a future version of BioSQL it would be nice to have CLOB rows for abstract and full text (Full text might need to be a BLOB depending on format). Obviously they could both be null.
Another column could indicate the MIME type of the BLOB:
BLOB abstract VARCHAR abstract_mime_type
Then if you stored a PDF in it you could set abstract_mime_type to 'application/x-pdf', or if it was plain text, you could set the abstract_mime_type to 'text/plain'.
See also the respective thread on the BioSQL mailing list.
Normalized bibliographic metadata for References
There should be individual author records instead of a single string, and possibly a full bibliographic record model.
Applied or fixed
Some character column widths are too narrow
Erik Jan reports that some varchar(n) type columns are constrained too narrow to accommodate the latest UniProt database.
Fix: expanded the column width of dbxref.accession and bioentry.accession to 128 in v1.0.1.