1.4 The Great Debate 7 4. 5. 6. 7. DMS-1100 from Univac DBMS32 from DEC (Digital Equipment Corporation) IMAGE/3000 from Hewlett-Packard (a port of TOTAL from the mainframes to HP3000 computers) IMS from IBM. This hierarchic DBMS is still a dominate database product that uses a tree data model. It may well have as much or more data in its files than SQL. I have given it Chapter 15 by itself. 1.3 Modeling a Graph in a Program Long before there was SQL, programmers represented graphs in the pro- gramming language that they had. People used pointer chains in assembly language or system development languages such as `C' to build very direct representations of graphs. However, the later, higher level languages, such as Pascal, LISP and PL/I, did not expose the hardware to the programmer , like the system development languages. Pointers in these languages were