Systems Application Architecture (SAA) was IBM's strategy for enterprise computing in the late 1980s and early 1990s. It was replaced and considerably expanded by IBM's Open Blueprint , an enterprise strategy for network computing. Both of these are structured views of the types of computing services that an enterprise may need, the relationships between these services, and specification of the standards and products that are envisioned as providing these services.
SAA defined three layers of service:
- Common User Access
- Common Programming Interface
- Common Communications Support
By using or creating applications and data that conformed to these three layers (provided by strategic IBM products), an enterprise could be assured of consistency and some amount of program portability among IBM's range of computer systems. As IBM, along with the rest of the computer industry, discovered the value of industry-wide standardization and open computing, the company revised its strategy. Its new strategy, the Open Blueprint, would recognize that customers wanted consistency and portability of programs and data across different manufacturers' systems, not just within IBM's systems. Two other trends not current when SAA was developed have influenced IBM's Open Blueprint: the client/server model of distributing computing and the concept and implementation of object-oriented programming . The Open Blueprint seems well positioned to absorb another new trend: network computing, including use of the Internet.
Since most of IBM's large customers have a large investment in legacy application s and data developed during the era of SAA and prior, IBM's Open Blueprint recognizes the need to support them. Notably, IBM's Systems Network Architecture ( SNA ), the keystone of the SAA Common Communications Support, is retained in the Open Blueprint as an alternative to TCP/IP . Other companies have also made investments in SAA, recognizing that IBM customers' legacy applications will not be going away soon and that in some cases these applications may represent the current best solution. Novell's Netware for SAA is an example of a widely-installed product that retains the SAA identity.