/**

* Provides abstract classes for modeling functions that execute and escape SQL query strings.

* To extend this QL library, create a QL class extending `SqlExecutionFunction` or `SqlEscapeFunction`

* with a characteristic predicate that selects the function or set of functions you are modeling.

* Within that class, override the predicates provided by the class to match the way a

* parameter flows into the function and, in the case of `SqlEscapeFunction`, out of the function.

*/

private import cpp

/**

* An abstract class that represents a function that executes an SQL query.

*/

abstract class SqlExecutionFunction extends Function {

/**

* Holds if `input` to this function represents SQL code to be executed.

*/

abstract predicate hasSqlArgument(FunctionInput input);

}

/**

* An abstract class that represents a function that is a barrier to an SQL query string.

*/

abstract class SqlBarrierFunction extends Function {

/**

* Holds if the `output` is a barrier to the SQL input `input` such that is it safe to pass to

* an `SqlExecutionFunction`.

*/

abstract predicate barrierSqlArgument(FunctionInput input, FunctionOutput output);

}