[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) an identifier.

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);
or example2.html for a bigger, more realistic illustration (small social network).

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)
 * "compact" (default) use the same box for an entity and its attributes

-----

**TODO** list:

 - functional integrity constraints (CIF)
 - inter-relations constraints (or, and, xor, inclusion)
 - inheritance with the right symbol (triangle)

*Implementation note:* temporary dependency to [underscore](http://underscorejs.org/); used only for its shuffle() method.
Commit	Line	Data
	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
	8	-----
	9
	10	An entity is defined as follow
	11
	12	[Entity]
	13	+attr1 (*)
	14	attr2 (*)
	15
	16	with (\*) = optional SQL indications, and + denoting a (part of) an identifier.
	17
	18	A relationship is defined in this way
	19
	20	{Relation}
	21	Entity C1
	22	Entity2 C2
	23	--
	24	attr1 (*)
	25	attr2 (*)
	26
	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
	31	* \+ = 1..n
	32	* 1 = 1..1
	33	* ? = 0..1
	34
	35	Special cardinalities are also available to indicate relative identification: `?R` and `1R`.
	36
	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
	43	To mark a weak entity, just surround its name by extra-brackets
	44
	45	[[WeakEntity]]
	46
	47	In the same way, a weak relation can be written
	48
	49	{{WeakRelation}}
	50
	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
	54
	55	is_a
	56	Animal Cat Fish
	57	Planet Mars Venus
	58
	59	Finally, blocks must be separated by new lines. For a usage example, see example.html (it should render as seen in example\_\*.svg);
	60	or example2.html for a bigger, more realistic illustration (small social network).
	61
	62	Note that the "drawMcd" method can take a second argument, which indicates the type of graph.
	63	* "bubble" draws the standard graph, as seen [here](https://en.wikipedia.org/wiki/Entity%E2%80%93relationship_model#/media/File:ER_Diagram_MMORPG.png)
	64	* "compact" (default) use the same box for an entity and its attributes
	65
	66	-----
	67
	68	TODO list:
	69
	70	- functional integrity constraints (CIF)
	71	- inter-relations constraints (or, and, xor, inclusion)
	72	- inheritance with the right symbol (triangle)
	73
	74	Implementation note: temporary dependency to [underscore](http://underscorejs.org/); used only for its shuffle() method.