====== Concepts and Relations ======
Let's start with a simple sentence:
  Fred's car is red.

Our goal is to produce this annotation:
{{:projects:content-annotation:tutorial:ex1.png|Fred's car is red.}}

We can see three nodes in this graph. They are identified by their IDs: ''C1'', ''C2'', and ''C4''.
Every node represents a concept. ''C1'' represents the person called //Fred//. ''C2'' represents his
car, and ''C4'' represents the notion of being red.

=== Concepts ===

Every concept has a bunch of attributes:
{{:projects:content-annotation:tutorial:concept1.png|the Fred's car}}

These attributes are described in [[projects:content-annotation:layer-attributes]] section.

But not every node has every attribute. It depends on the [[projects:content-annotation:layer-attributes:sort:hierarchy-of-sorts|sort]] of the concept. For instance, the property ''red'' has no other attribute than the sort.

=== Relations ===

The concepts in the example are connected by **edges**. These edges represent **relations**, e.g. Fred is connected with his car by a [[projects:content-annotation:relations:POSS]] relation. By definition, the edge goes from the owner to the owned object. If we created an edge with reverse direction, it would mean that the car possesses Fred.

=== Functions ===

Beside of Concepts and Relations, the last part of MultiNet lies in Functions as in this example:
   Fred goes by his car, or by train.

{{:projects:content-annotation:tutorial:ex2.png|Fred goes by his car, or by train.}}

The function [[projects:content-annotation:functions:VEL2]] generates a concept representing disjunction of its arguments. Here concept ''F8'' is either ''C2'' (car), or ''C9'' (train). None of ''C2'' and ''C9'' is an appropriate candidate to connect to ''go'' with the [[projects:content-annotation:relations:INSTR]] relation. We need a function to create this content representation.