DAS and their list of Global Sequence Identifiers
The Distributed Annotation System (DAS, or BioDAS) defines a communication protocol used to exchange annotations on genomic or protein sequences. It is motivated by the idea that such annotations should not be provided by single centralized databases, but should instead be spread over multiple sites. Data distribution, performed by DAS servers, is separated from visualization, which is done by DAS clients. The advantages of this system are that control over the data is retained by data providers, data is freed from the constraints of specific organisations and the normal issues of release cycles, API updates and data duplication are avoided.
The DAS/2 specification describes how different annotations servers can make annotations on the same genomic sequence. It uses a set of globally defined names to label each segment. A DAS client merges data from two annotation servers if they both use segments having the same global reference name.