This is Sogeti's reference architecture model called Digitecture, which defines how integration tiers of omnichannel services can help meet the demand of fast-moving touch points (e.g. webs and apps) even if the legacy back-end systems can't keep up.
Starting from the bottom of the model are the back-end systems:they are hard to change and they change slowly. It could also be external services, and this will become more common as the traditional linear value chain is transformed into a dynamic ecosystem where each player cooperates with others to bring value to the customer.
Then we have the low-end services that use the back-end systems to deliver generic functionalities (most often data-oriented) and information according to a consolidated (master) data model. That way we can get a unified view of a customer and a product even if the back-end systems have different or even conflicting definitions.
The high-end services use these low-end services and add logic, which may include processes, for a certain business domain, like order handling or booking. These services deliver generic functionalities and usually all available information (attributes), and are not implemented to meet a specific user scenario. Low-end and high-end services are usually developed by a team that is not part of any specific project to implement a touch point.
The front-end services, on the other hand, are usually built as part of the touch point project, and their purpose is to use the high-end services to support the touch point with specific functionalities and information for each user scenario. The main benefit of this tier, which is often referred to as an API, is that it prevents the implementers of the touch point from solving things on the client side (when mobile, often on multiple platforms) that should be handled on the server-side. Thereby solving the problems that comes from trying to implement high-end services that can meet all the needs of the touch points.
A security framework is available to all tiers, providing support for confidentiality, integrity, authentication, authorization, availability, traceability, compliance, etc, and there is also a management framework that supports governance and operation of the platform using self-service as much as possible.
The background is the mindset of people shifting to an expectation that any need in the current context can be fulfilled immediately, most organization are focused on meeting that expectation by changing how their people work and the technical solutions to support that. Many have therefore started a digital transformation journey, and soon come to the conclusion that their legacy back-end systems cannot keep up with the needs of the business and its customers.
There is also a need to get a unified view of the most important information, like a single view of the customer, and functionalities that can be used in multiple channels.