The Application Interface Specification (AIS) is a collection of open specifications that define the application programming interfaces (APIs) for high-availability application computer software.
High-availability clusters (also known as HA clusters or fail-over clusters) are groups of computers that support server applications that can be reliably utilized with a minimum amount of down-time.
Middleware in the context of distributed applications is software that provides services beyond those provided by the operating system to enable the various components of a distributed system to communicate and manage data.
The Service Availability Forum (SAF or SA Forum) is a consortium that develops, publishes, educates on and promotes open specifications for carrier-grade and mission-critical systems.
Veritas Cluster Server (rebranded as Veritas Infoscale Availabilty and also known as VCS and also sold bundled in the SFHA product) is a high-availability cluster software for Unix, Linux and Microsoft Windows computer systems, created by Veritas Technologies.