Designers still have the option of three-tier or n-tier application designs; but, they now have the two-tier option again. The sim- plicity of two-tier client/server is attractive, but security issues (databases have huge attack surfaces) may cause many designers to want three-tier server architectures with the web server in the demilitarized zone (DMZ). It is likely that web services will be the way we federate heteroge- neous database systems. .