legend_classes.uml

@startuml

!include default_style.iuml

title UML Class diagram and object diagram explained

'-----------------------------------------------------------------------
' Display configuration

' hide members
hide methods

'-----------------------------------------------------------------------
' Classes
package "Conceptual data model (class diagram)" {

class Users {
  id : string
  username: string
  ...
}

note top of Users #orange
- **Attributes** can be described
  **in your preferred type language**
  (eg. SQL, PHP, Java, C++, etc.).
  Just copy and paste your defined
  types from your **source code**
  (a bit **informal but very useful**)
end note

abstract class Contents
note top of Contents #orange
- Any instance of an abstract class
  **is an instance of one of its**
  **subclasses**
end note

class JobOffers {
  id : string
  ...
}

class Posts {
  id : string
  ...
}

class Publications {
  id : string
  ...
}

'-----------------------------------------------------------------------
' Associations

Contents <|-- JobOffers
Contents <|-- Posts

Users "1" *- "authorOf\r*" Contents: createdBy <
note top on link #orange
- The **association name** can
  always be used **as a role** in
  involved classes
- The meaning of decorating an
  association with a **triangle** is
  to use its **name as a role** in
  the indicated **orientation** (eg.
  p2.publisher, post2.createdBy...)
end note

Contents "1" -- "publishedIn\l0..1" Publications : content <
note right on link #orange
- An extra role has been included to
  illustrate the use of roles
  (eg. publishedIn)
- **Roles used to indicate** the name of
  the **artifacts in concrete**
  **implementations** (tables relational
  model; sets, hashes, indices in NoSQL
  models, etc.)
end note

Users "1" *-- "publications\l*" Publications : publisher <
note right on link #orange
- The meaning of **composition**
  (represented with a **filled diamond**)
  is that any instance must be a
  **component of only one owner**
  (even under multiple classes of
  potential owners).
- Aliases for multiplicities:
  **1 = 1..1**, *** = 0..***
- In this diagrams **aggregation**
  (**unfilled diamond**) is not used
  since it has no formal semantics
  ("Think of it as a modeling placebo"
  [Rumbaugh, UML Reference]).
end note

note as publisher_implementation
Example indicating implementations:
- Publication:publisher implemented as
  a property in a hash in Redis
- Users:publications implemented as
  a set in Redis
- Publication:publisher implemented as
  not null column in table *publications*
- Users:publications implemented as
  a SQL view inspecting table
  *publications*
end note

Users .. publisher_implementation
publisher_implementation . Publications

}


'-----------------------------------------------------------------------
legend right

- Aggregation (represented with a blank diamond) is not used since
  it is **strictly meaningless** (as Martin Fowler says in UML
  Distilled).
' - The meaning of composition (represented with a filled diamond) is that
'   any instance must be a component of only one owner (even under multiple
'   classes of potential owners).
' - Aliases for multiplicities: 1 = 1..1, * = 0..*
' - Expressions {...} represents (mathematical) sets (no arrays, no
'   tuples, no hashes, no artifacts in any physical or logical model)
' - The name of the association can always be used as a role
'   in classes involved in the association
' - The meaning of decorating an association with a triangle is to use its
'   name as a role in the indicated orientation  (eg. p2.publisher,
'   post2.createdBy...)
' - An extra role has been included to illustrate the use of roles
' - Roles used to indicates the name of the artifacts in concrete
'   implementations (tables relational model, sets or hashed in NoSQL
'   models, etc.)
' - Roles and attributes follow the same syntax
' - Attributes can be described in your preferred type language (eg. SQL,
'   PHP, Java, C++, etc.). Just copy and paste your defined types from
'   your source code (a bit informal but very useful)
' - When relevant, you can add attribute values in class instances

end legend

@enduml