Better graph rendering by randomizing appearances and links left/right in dot string
[erdiag.git] / README.md
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 *Note:* at the moment only the conceptual graph is implemented, and no comments are allowed in textual descriptions.
9 At least the former is planned, and also probably a way to indicate relative identifiers, and maybe links between relationships.
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11 *Note bis:* temporary dependency to [underscore](http://underscorejs.org/); good library but used so far only for its shuffle() method.
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13 -----
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15 An entity is defined as follow
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17 [Entity]
18 #attr1 (*)
19 attr2 (*)
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21 with (\*) = optional SQL indications, and # denoting a (part of) a key.
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23 A relationship is defined in this way
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25 {Relation}
26 Entity C1
27 Entity2 C2
28 --
29 attr1 (*)
30 attr2 (*)
31
32 where attributes are optional, and C1 (resp. C2) = cardinality for entity 1 (resp. 2).
33 Defining relationships with more than two attributes is easy: just add entities.
34 Cardinality dictionary:
35 * \* = 0..n
36 * \+ = 1..n
37 * 1 = 1..1
38 * ? = 0..1
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40 To mark a weak entity, just surround its name by extra-brackets
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42 [[WeakEntity]]
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44 In the same way, a weak relation can be written
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46 {{WeakRelation}}
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48 The syntax for these two last is then the same as in the non-weak versions.
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50 To indicate an inheritance relation, proceed as follow
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52 is_a
53 Animal Cat Fish
54 Planet Mars Venus
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56 Finally, blocks must be separated by new lines. For a usage example, see example.html (it should render as seen in example.svg)
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58 Note that the "drawMcd" method can take a second argument, which indicates the type of graph.
59 * "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
60 * "compact" (default) use the same box for an entity and its attributes