O.R. Oberdorf, J.L. Herrero, M.A. Conroy, J.C. McDowell
SAO
The Data Model for the ASC flight system is presented. The data model provides an abstract description of AXAF datasets. Through the data model API tools and applications will have efficient and transparent access to heterogeneous disk formats. To accomplish this, the data model will use a layered library design. The bottom layer will provide a uniform interface for each kind of disk file that needs to be accessed. This ``kernel'' leyer will contain all of the low level file I/O routines. There will be one kernel per supported physical format. The middle layer will hide the disk file concept and provide access to the logical data objects.Higher layers will put meaning to the objects provided by the middle layer to build more powerful objects, and/or mission specific data constructs.