SBASE is a collection of protein domain sequences collected from the literature, from protein sequence databases and from genomic databases. The protein domains are defined by their sequence boundaries given by the publishing authors or in one of the primary sequence databases (Swiss-Prot, PIR, TREMBL etc.). Domain groups are included if they have well defined sequence boundaries, and if they can be distinguished from other sequences using a similarity search technique.

The SBASE database uses a set theoretical approach for representing similarities, which in practical terms is extremely simple. Sequences are considered similar if they are members of a similarity group in which all or most sequences are similar to each other and less similar to other members of the database. Sequences that have an above threshold BLAST similarity score to at least one member of the group is called the neighbourhood of the group.

SBASE contains the domain sequences as well as various statistical parameters of the domain groups. In terms of pattern recognition, this approach is similar to the memory-based computing paradigm. Since the neighbourhoods of the domain groups are represented as a network of their similarities, it can also be called a similarity network based approach.

SBASE is developped by ICGEB in Trieste, Italy.