[erdiag.git] / README.md

# erdiag: Entity-Relationship Diagrams Generator

Inspired by [this repository](https://code.google.com/archive/p/merisier/).

This parser reads ER diagrams definition files, and produces two types of diagrams + SQL code.
[Graphviz](https://www.graphviz.org/) is used on server side to translate parsed graph descriptions into SVG objects.

-----

An entity is defined as follow

	[Entity]
	#attr1 (*)
	attr2 (*)

with (\*) = optional SQL indications, and # denoting a (part of) a key.

A relationship is defined in this way

	{Relation}
	Entity C1
	Entity2 C2
	--
	attr1 (*)
	attr2 (*)

where attributes are optional, and C1 (resp. C2) = cardinality for entity 1 (resp. 2).
Defining relationships with more than two attributes is easy: just add entities.
Cardinality dictionary:
 * \* = 0..n
 * \+ = 1..n
 * 1 = 1..1
 * ? = 0..1

Special cardinalities are also available to indicate relative identification: `?R` and `1R`.

And, in case of a self-relationship, symbols '>' and '<' can indicate the sense, as in

	{manage}
	Users *>
	Users 1<

To mark a weak entity, just surround its name by extra-brackets

	[[WeakEntity]]

In the same way, a weak relation can be written

	{{WeakRelation}}

The syntax for these two last is then the same as in the non-weak versions.

To indicate an inheritance relation, proceed as follow

	is_a
	Animal Cat Fish
	Planet Mars Venus

Finally, blocks must be separated by new lines. For a usage example, see example.html (it should render as seen in example\_\*.svg)

Note that the "drawMcd" method can take a second argument, which indicates the type of graph.
 * "bubble" draws the standard graph, as seen [here](https://en.wikipedia.org/wiki/Entity%E2%80%93relationship_model#/media/File:ER_Diagram_MMORPG.png) for example
 * "compact" (default) use the same box for an entity and its attributes

-----

**TODO** list:

 - functional integrity constraints (CIF)
 - inter-relations constraints (or, and, xor...)
 - inheritance with the right symbol (triangle)
 - put online somewhere (user enter graph description and get SVG + SQL)

*Implementation note:* temporary dependency to [underscore](http://underscorejs.org/); good library but used so far only for its shuffle() method.
Commit	Line	Data
525c4d2a BA	1	# erdiag: Entity-Relationship Diagrams Generator
	2
	3	Inspired by [this repository](https://code.google.com/archive/p/merisier/).
	4
	5	This parser reads ER diagrams definition files, and produces two types of diagrams + SQL code.
	6	[Graphviz](https://www.graphviz.org/) is used on server side to translate parsed graph descriptions into SVG objects.
	7
525c4d2a BA	8	-----
	9
	10	An entity is defined as follow
fe021b27	11
bf4fc3ed BA	12	[Entity]
	13	#attr1 (*)
	14	attr2 (*)
fe021b27	15
525c4d2a BA	16	with (\*) = optional SQL indications, and # denoting a (part of) a key.
	17
	18	A relationship is defined in this way
fe021b27	19
bf4fc3ed BA	20	{Relation}
	21	Entity C1
	22	Entity2 C2
	23	--
	24	attr1 (*)
	25	attr2 (*)
fe021b27	26
525c4d2a BA	27	where attributes are optional, and C1 (resp. C2) = cardinality for entity 1 (resp. 2).
	28	Defining relationships with more than two attributes is easy: just add entities.
	29	Cardinality dictionary:
	30	* \* = 0..n
fe021b27	31	* \+ = 1..n
525c4d2a BA	32	* 1 = 1..1
	33	* ? = 0..1
	34
19addd10 BA	35	Special cardinalities are also available to indicate relative identification: `?R` and `1R`.
19addd10 BA	36
7a80e6db BA	37	And, in case of a self-relationship, symbols '>' and '<' can indicate the sense, as in
	38
	39	{manage}
	40	Users *>
	41	Users 1<
	42
525c4d2a	43	To mark a weak entity, just surround its name by extra-brackets
fe021b27	44
525c4d2a	45	[[WeakEntity]]
fe021b27	46
525c4d2a	47	In the same way, a weak relation can be written
fe021b27	48
525c4d2a	49	{{WeakRelation}}
fe021b27	50
525c4d2a BA	51	The syntax for these two last is then the same as in the non-weak versions.
	52
	53	To indicate an inheritance relation, proceed as follow
fe021b27	54
bf4fc3ed BA	55	is_a
	56	Animal Cat Fish
	57	Planet Mars Venus
525c4d2a	58
3ca1e50c	59	Finally, blocks must be separated by new lines. For a usage example, see example.html (it should render as seen in example\_\*.svg)
525c4d2a BA	60
	61	Note that the "drawMcd" method can take a second argument, which indicates the type of graph.
	62	* "bubble" draws the standard graph, as seen [here](https://en.wikipedia.org/wiki/Entity%E2%80%93relationship_model#/media/File:ER_Diagram_MMORPG.png) for example
	63	* "compact" (default) use the same box for an entity and its attributes
5fe4fa10 BA	64
	65	-----
	66
	67	TODO list:
	68
	69	- functional integrity constraints (CIF)
	70	- inter-relations constraints (or, and, xor...)
	71	- inheritance with the right symbol (triangle)
	72	- put online somewhere (user enter graph description and get SVG + SQL)
	73
	74	Implementation note: temporary dependency to [underscore](http://underscorejs.org/); good library but used so far only for its shuffle() method.