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 -----
   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) a key.
  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
  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
  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.