Index consideration for date effective tables

it is a best practice to add ValidTo to the ValidTimeStateKey index
and on the Properties tab (of the ValidTo field in the index) to
select Yes from the Included Column.

[see: http://dev.goshoom.net/en/2012/04/included-columns-in-ax2012]

but if it is a clustered index see this:

Performance considerations when designing valid time state tables
To help improve performance of valid time state tables, you should index them correctly.
Valid time state tables are modeled with an alternate key that includes the ValidFrom column.
In some models, the ValidTo column may have also be included in the alternate key,
but this is not necessary for uniqueness, and it should be removed from the alternate key constraint.
If the ValidFrom column is a key column of the clustered index,
the ValidTo column should not also be a key column of the clustered index.
If the ValidFrom column is a key column of a non-clustered index,
the ValidTo column should be made an included column in the non-clustered index,
which provides coverage for range queries that involve both ValidTo and ValidFrom columns.

for examples see where the index is a clustered index see:
\Data Dictionary\Tables\LogisticsPostalAddress

or see
\Data Dictionary\Tables\HcmPositionWorkerAssignment

SysExtension framework for Dynamics Ax example

The benefits of using this new extension model are that the base and derived classes are decoupled, and it takes less code to extend the capability of the Microsoft Dynamics AX application.

The getClassFromSysAttribute method works by searching through the classes that are derived from the our base class (EF_ExtFrameworkSample6) until it finds a class that has matching attribute

The input value of the attribute class can be anything, an enum, a string, an integer. For this example I used the class name as input.

1) Create the attribute class

As you see I added in the attribute class also a generic static method that can be used by any extension that might use this attribute

class EF_ClassNameAttribute extends SysAttribute
{
    ClassName className;
}
public void new(ClassName _className)
{
    super();
    className = _className;
}
public ClassName parmClassName(ClassName _className = className)
{
    className = _className;

    return className;
}
//this method should be in the factory class, not here.
//I took the liberty to put it here becuse I might want to share it with multiple factory classes.
public static Object getClassFromSysAttribute(ClassName _baseClassName, ClassName _className)
{
    EF_ClassNameAttribute attr;
    Object cl;

    attr = new EF_ClassNameAttribute(_className);
    cl = SysExtensionAppClassFactory::getClassFromSysAttribute(_baseClassName, attr);

    if (!cl)
    {
        throw error(Error::wrongUseOfFunction(_baseClassName));
    }

    return cl;
}

2) Create the base class

the base class does not need to be abstract, but is a good practice

abstract class EF_ExtFrameworkSample6
{
    Name name;
    MethodName functionName;
}
abstract protected void init()
{
}
public void run()
{
    this.init();
    info(strFmt('Hello my name is %1', name));
    info(strFmt('the class that run is %1', functionName));
}

3) Create the Extensions

[EF_ClassNameAttribute(classStr(EF_ExtFrameworkSample6_1))]
class EF_ExtFrameworkSample6_1 extends EF_ExtFrameworkSample6
{
}
protected void init()
{
    name = 'Pippo';
    functionName = funcName();
}

[EF_ClassNameAttribute(classStr(EF_ExtFrameworkSample6_2))]
class EF_ExtFrameworkSample6_2 extends EF_ExtFrameworkSample6
{
}
protected void init()
{
    name = 'Topolino';
    functionName = funcName();
}

4) Create the Factory class

class EF_ExtFrameworkSample6Factory
{
}
protected void new()
{
}
public static EF_ExtFrameworkSample6 newFromClassName(ClassName _className)
{
    return EF_ClassNameAttribute::getClassFromSysAttribute(classStr(EF_ExtFrameworkSample6), _className);
}
public static EF_ExtFrameworkSample6 newFromSample6_1()
{
    return EF_ExtFrameworkSample6Factory::newFromClassName(classStr(EF_ExtFrameworkSample6_1));
}
public static EF_ExtFrameworkSample6 newFromSample6_2()
{
    return EF_ExtFrameworkSample6Factory::newFromClassName(classStr(EF_ExtFrameworkSample6_2));
}
//just for trials...
public static void main(Args _args)
{
    EF_ExtFrameworkSample6 cl;
    cl = EF_ExtFrameworkSample6Factory::newFromSample6_1();
    cl.run();
}

One side note, The extension framework cache so every time you do some changes during development clear the cache :

static void JobEF_SysExtensionCache(Args _args)
{
    SysExtensionCache::clearAllScopes();
}