removing default mapping sections (#133)

spec/docs/overview.md

@@ -85,9 +85,6 @@ as defined throughout this specification.
 A resource SHOULD NOT be typed as an RML class
 if it does not meet the definition of that class.
 
-The [default mapping]() SHOULD be such that
-its output is the [Direct Graph]() [[DM]()] corresponding to the [input data source]().
-
 
 ## RDF-based Turtle Syntax; Media Type
 

spec/docs/tooling.md

@@ -50,15 +50,6 @@ that are raised in the process of generating the output dataset.
 An [RML processor]() MAY include an [RML data validator](), but this is not required.
 
 
-### Generators
-
-An [RML processor]() MAY include an **_RML default mapping generator_**.
-This is a facility that introspects the schema of the [input data source]()
-and generates an [=RML mapping=], 
-possibly in the form of an [RML mapping document](),
-intended for further customization by a mapping author.
-Such a mapping is known as a <dfn>default mapping</dfn>.
-
 ## Data Errors
 
 A <dfn>data error</dfn> is a condition of the data in the [input data]()