The ALSE IP provides an efficient way to interconnect an Altera FPGA with a Xilinx/AMD FPGA. Complete interoperability with the Xilinx IP is guaranteed.
It can also be used to interconnect two Altera FPGAs together, in replacement of other proprietary or complex High-Speed Serial protocols (like Serial Lite IV or PCIExpress).
Another use case would be an Altera High-End or mid-range FPGA to low cost or very low power FPGA from another vendor.