Migration of a Chosen Architectural Pattern to Service Oriented ...

Chapter 3. Architectural Patterns 44Layer – A layer encapsulates common logic on the same level of abstraction.Each layer provides an interface allowing another layer to cal its functionality.Relationships – A layer can use other layer only if they are connected.There are uni and bi directional relations between layers. This pattern ischaracterized by lack of direct calls of layers to non-neighbor layers. If thelayer number one wants to call the method from the layer number threeand there is no direct connection between them, the layer number one hasto call the layer number two in order to call the layer number three. Alayer can invoke only a layer that is bellow or above this layer. Connectionlimited to only upper and lower layer increases maintainability but reducesperformance (see figure 3.6).Layer 1Layer 2Layer 3Figure 3.6: Example usage of Layer pattern2. Pipe and filtersOverview – The pattern is characterized by a good and efficient way ofdata processing but the structure of the pattern reduces its reliability becauseif one of the filters fails, the whole process fails as well.ElementsFilter – processes data. A filter can push data to a pipe or pull it out froma pipe.