ER Markup Language And Compiler

###Author: Ganesh Prasad Sahoo

6th Semester B.Tech

Computer Science and Engineering

National Institute of Technology, Rourkela

Background

ER Markup language is a textual framework to represent Entities and Relationships. This project started as a weekend project to avoid MS Visio for drawing ER Diagrams. I had very low diskspace and no wish to switch from Linux to Windows again just for a piece software that would enable me to to do one thing in particular - "Drawing ER Diagrams", that too for a class assignment. So I decided on designing and developing something lighter and more productive for this specific task and started writing Grammar Productions for the same. After about one and half days of work, I was sitting on some 500 lines of code which compiled my ER Diagram Descriptions written in the ER Markup Language to Graphviz dot language.

GRAMMAR SPECIFICATIONS

PROGRAM -> DIAGRAM name; BEGIN (ENTITY+RELATION)+ END

ENTITY -> ENT name [WEAK] ;
			| ENT name [WEAK] { ATTRIBUTE* } 
			
ATTRIBUTE -> ATTR name (TAG)* ;
			| ATTR name COMPOSITE { ATTRIBUTE* }
			
RELATION -> RELN name [WEAK] FROM { EDGE+ } TO { EDGE+ } ;

EDGE -> CONNECT name EDGETYPE* ;

TAG -> WEAK | MULTI | KEY | DERIVED 

EDGETYPE -> PARTIAL | TOTAL | ONE | MANY 

comments start with #

USAGE

Build the executable 'erdcc' with make.

Then run 'erdcc < source file in ER Markup > < Outputfile >'

This will give you a Dot file describing nodes and edges of the ER Diagram. For best results, render this Dot file with Graphviz fdp engine.

EXAMPLE

# Test code in ER Markup Language
DIAGRAM test;
BEGIN
ENT I{
	ATTR Consciousness;
	ATTR "Knowledge" DERIVED;
	ATTR self KEY;
}

ENT God{
	ATTR "Everything" KEY COMPOSITE{
		ATTR Universe;
		ATTR I KEY;
	}
	ATTR Reality;
}

RELN Conceived 	FROM{ CONNECT I MANY; }	TO { CONNECT God ONE; };
RELN Created FROM{ CONNECT God ONE; } TO { CONNECT I MANY; };

ENT Book{
	ATTR Name;
	ATTR ISBN KEY;
	ATTR Price;
	ATTR Author MULTI;
}

RELN Write FROM { CONNECT I MANY; } TO { CONNECT Book MANY; };
RELN Read FROM { CONNECT I MANY; } TO { CONNECT Book MANY; };

ENT Software{
	ATTR Name;
	ATTR "Written in (Language)" MULTI;
	ATTR "Interface CLI/TUI/GUI" MULTI;
	ATTR Bugs MULTI;
	ATTR Programmer MULTI;
}

RELN Write FROM { CONNECT I ONE; } TO { CONNECT Software MANY; };

END