The SI2 program includes four classes of awards:
Scientific Software Elements (SSE): SSE awards are Software Elements. They target small groups that will create and deploy robust software elements for which there is a demonstrated need that will advance one or more significant areas of science and engineering.
Scientific Software Integration (SSI): SSI awards are Software Frameworks. They target larger, interdisciplinary teams organized around the development and application of common software infrastructure aimed at solving common research problems. SSI awards will result in sustainable community software frameworks serving a diverse community.
Scientific Software Innovation Institutes (S2I2): S2I2 awards are Software Institutes. They focus on the establishment of long-term hubs of excellence in software infrastructure and technologies that will serve a research community of substantial size and disciplinary breadth.
Reuse: In addition, SI2 provides support through a variety of mechanisms (including co-funding and supplements) to proposals from other programs that include, as an explicit outcome, reuse of software. Proposals that integrate with previously developed software, either by reference or inclusion, are encouraged. Proposals developing new software with an explicitly open design for reuse may also be considered. The purpose of the Reuse class is to stimulate connections within the broader software ecosystem. The class of reuse awards is currently being developed.
Multidisciplinary projects at the SSE, SSI, and S2I2 levels should be submitted to the appropriate SI2 solicitation.