For the last decade, the aggregation of different component systems or subsystems that cooperate to deliver a whole functionality has been the focus of industries that use technology. This is known as the modular approach to systems building, and the SI process has always been at the near-end of the development cycle. Because systems or subsystems to be integrated may span different fields in software and hardware engineering, a SI engineer must have a broad range of skills and breadth of knowledge.

SI methods are as follows:

• Horizontal Integration: Involves the creation of a unique subsystem that is meant to be the single interface between all other subsystems, ensuring that there is only one interface between any subsystem and any may be replaced with another without affecting the others by using totally different data and interfaces. This is also known as an Enterprise Service Bus (ESB).
• Vertical Integration: Subsystems are integrated according to functionality by creating "silos" of functional entities, beginning with the bottom basic function upward (vertical). This very quick method only involves a few vendors and developers but becomes more expensive over time because to implement new functionalities, new silos must be created.
• Star Integration: Also known as "Spaghetti Integration" because each subsystem is connected to multiple subsystems, so that the diagrams of the interconnections look like a star. However, the more subsystems there are, the more connections are made, and it ends up looking like spaghetti.
• Common Data Format: Helps the system avoid having the adapter convert to and from every application format. Systems using this method set a common or application-independent format, or they provide a service that does the transformation to or from one application into the common application.