Ensembl makes use of the DAS in two ways:
The Distributed Annotation System (DAS) is a client-server system that has been initially designed for the exchange of biological annotation information based on a standard protocol. DAS provides thus a standardised method to serve custom annotation information and to integrate data sets for display in other resources. Ensembl allows attachment and configuration of external DAS sources to several Ensembl genome browser displays:
Several DAS resources provided by the European Bioinformatics Institute and the Wellcome Trust Sanger Institute are already available and pre-configured by default. To turn these on and off:
Further annotation information resources can be integrated into Ensembl by attaching a valid data source provided by a DAS annotation server. To attach a DAS source:
Whilst DAS was originally designed to exchange annotations of reference sequences in chromosome or clone coordinate systems, GeneDAS and ProteinDAS are extensions to the DAS protocol used to exchange gene and protein annotations independent of genomic location information. Currently, Ensembl supports annotations based on several different coordinate systems. Some coordinate systems allow annotations which are positional in nature (i.e. refer to a location within a sequence), whereas others are concerned with text-based non-positional annotations.
The views that a particular DAS source may be displayed on depends on the data being served and the coordinate system of its annotations:
Ensembl supports DAS on the following sections of the website:
The extended DAS specification supported by Ensembl is described in Jenkinson AM et al., BMC Bioinformatics, 2008;9(Suppl 8):S3.
Ensembl provides a DAS reference server which gives access to genomic sequences, the latest Ensembl gene predictions, and for some species, karyotypes and ditags. A list of the sources currently served from the Ensembl DAS reference server may be found as XML documents at:
DAS request URLs have a specific format:
protocol://site-prefix/das/data-source/command?arguments
For example:
For more information on the DAS protocol, see our main DAS documentation.