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

Chapter 3. Architectural Patterns 42source. Those patterns are not taken into consideration during next steps. Thetable contains also Publisher-Subscriber. Publisher–Subscriber is also rejectedbecause it is a known design pattern [22][34] while the table should contain onlyarchitectural patterns. This exception is important because it confirms previouslyaddressed problem that says that it can be very hard to distinguish both architecturaland design patterns from each other. Moreover, authors of the secondsource claim that all architectural patterns were checked before in terms of theiradherence to domain of architectural patterns. This finding means that othersources may also present a design pattern as an architectural pattern.3.2 CategorisationIn the previous section, nineteen architectural patterns out of thirty two werechosen. Analysis of feasibility of migration of this number of architectural patternswould require a lot of effort, consequently, the number of pattern will bereduced during the next selection. The selection is based on categorisation ofpatterns. The patterns are grouped and the most general pattern is chosen as arepresentative. This approach reduces considerably amount of patterns to analyse.The most general means that a pattern can be compared to other patternsbecause they have similar structure and purpose. Additionally, its structure isthe simplest. The representatives of each category reconsidered in next sections.This section presents process of selection of representatives of categories. Thesection is organized in following manner:1. Description of selected Architectural Patterns – the subsection provides descriptionsof patterns selected in the previous section. Each description hasfour elements: overview, elements and relationships between elements. Additionallya picture presenting an example usage of a pattern is provided.Since P. Avgerious in opposite to authors of other sources does not providedescriptions of patterns in his work, the descriptions and pictures base onremaining two sources of patterns.2. Methods of patterns categorisation – this subsection presents shortly identifiedways of pattern categorisation. Since creation of own categorisationmethod is not in scope of the work, one of presented approach is chosen.3. Allocation of pattern to categories – the purpose of this subsection is to allocatepatterns described in the first subsection to categories of categorisationmethod selected in the second subsection.4. Selection of representatives – this section provides comparison of patternswithin categories. As the result of comparison, representatives of categoriesare selected. The pattern for migration will be selected from those representatives.