Model Driven Architecture(Layer)

Microsoft Dynamics AX is designed with a unique layer and model structure that
separates and controls the updates and modifications made in the application.
This structure provides a powerful and flexible architecture for developing
business logic.
The key benefit of the layer and model structure is that it lets developers change
and extend the functionality in Microsoft Dynamics AX while maintaining
upgradability to new versions.
LayersApplication object layers hold all elements that are displayed in the AOT. There
are eight application object layers available. Each of these layers also has a patch
layer making a total of sixteen layers.
Layers are a hierarchy of levels in the application you can use to make
modifications and additions without interfering with the application elements in
the next lower level. When you make an element modification on one level, the
modification overshadows the element on a lower level. When the application is
compiled, only the top-level version of an application element is used.
There are three layers available only to Microsoft to deliver the base application.
(The xxP layer indicates the patch layer for each application object layer).
.

Layer	Description
SYS, SYP	System layer: The standard application is developed in this lowest layer. This includes the core application and the localization for most countries.
GLS, GLP	Globalization layer: Includes features developed for some countries that were not yet moved into the SYS layer.
FPK, FPP	Feature Pack layer: Includes industry feature packs that are controlled by Microsoft.

There are three layers available to partners and ISVs.

Layer	Description
SLN, SLP	Solution layer: Includes Microsoft endorsed industry solutions.
ISV, ISP	Independent Software Vendor layer: Includes generic or vertical solutions developed by ISV's.
VAR, VAP	Value Added Reseller layer: Includes multi-customer solutions developed by VAR's.

There are two layers available to both partners and customers who have a license
to access the AX source code.

Layer	Description
CUS, CUP	Customer layer: Includes customer specific functionality.
USR, USP	User layer: Includes installation specific functionality and customizations.

Benefits of Layers: Source Code ProtectionThe elements in the standard implementation (SYS, GLS, FPK layers) can only
be changed or deleted by the Microsoft Dynamics AX Development team.
The layers help protect the original source code and keep it separate from
modifications.
Similarly, ISV solution code is separated in a model within the ISV layer. Any
customer specific changes to the ISV solution would be in a higher layer.
Benefits of Layers: Faster and Easier UpgradesUpgrades and service packs contain changes in the lower layers where the base
code resides. This means that any changes by partners or customers are
maintained throughout the upgrade. Powerful compare and merge tools are
available to guide developers through the upgrade. These tools highlight
elements that are modified in higher layers and therefore might require some
action to merge the changes.
As an example:• The item number is an extended data type that exists in the SYS
layer. This field is a string which is 20 characters in length.• If a company that uses Microsoft Dynamics AX requires 30
characters for their item numbers, the field length would be changed
to 30 characters and the change saved in the CUS layer. The item
number data type now exists in both the SYS layer and the CUS
layer. The CUS layer is a higher layer so when the application is
compiled, the 30 character length is used.• If in a future version, Microsoft extends the length of the item field
to 40 characters, the upgrade tool would highlight that there is a
change in the SYS layer to 40 characters and there is an existing
change in the CUS layer to 30 characters. The developer would then
have the option to keep the CUS layer change or delete the CUS
layer and revert to the new field length in the SYS layer of the new
release.
Best Regards,
Hossein Karimi