University of Twente Analysis Patterns

University of Twente Software Reuse  Reuse is difficult and expensive Often does not pay off (quickly) Because it requires generic components vWhich are expensive to make vWhich requires broad domain knowledge  But reuse need not be done only at the code level!

University of Twente Software Reuse  Reuse can also take place at the level of: Designs: vdesign patterns & idioms vDocumentation of solutions Architectures (incl. Architecural patterns) Analysis: vAnalysis models of common (within a domain) structures & models

University of Twente Analysis Patterns  Analysis patterns.. Are solutions to common analysis problems vUse pattern format to describe domain knowledge vTypically at higher abstraction level This provides reuse of analysis models But also creates opportunities for better software reuse! vBecause of 'common analysis problems' scope

University of Twente Analysis Patterns Characteristics/how to use Analysis scope: vTry to understand & model the problem (domain) vBut the boundaries are fuzzy (not important) vSometimes even implementation examples The analysis patterns are 'useful' vNot right/wrong vA starting point, not destination

University of Twente Analysis Patterns How to Apply Analysis patterns suggest: vIntroduction of new classes, associations & interfaces vAnalysis patterns are about interfaces, not implementations Often come in groups vfor a particular domain vWith varying complexity  To be applied as needed

University of Twente Example: Accountability AP  Accountability Is a series of patterns To model "specific relationship between two parties for a given time period" vE.g. employment, leasing & service contracts  Why not use OO/UML associations?

University of Twente Accountability Why no explicit structure?  Example:  But: Not effective if there is much common interaction behavior between organization elements (parties) Embeds current organizational structure in design

University of Twente Accountability AP: Organization Hierarchy If the elements in the organization (mostly) share the same behavior: Is very flexible w.r.t. organization structure

University of Twente Accountability AP: Party Generalize to include persons vRight: If hierarchy association between organizational elements & with persons is similar

University of Twente Accountability AP: Accountability If several different links between elements vBut multiple hierarchies is not desirable

University of Twente ConclusionsConclusions Patterns can express knowledge at any level vOf the software development process Comparing Design Patterns to Analysis Patterns: vThe common design patterns are usually more generic (they encapsulate generic –OO-- design knowledge) vThe discussion of consequences and applicability of DPs is more elaborate (implementation issues).

University of Twente Exercise: Quantity AP  Read the Quantity AP Think of 3 suitable examples when to apply Why/when is Money (not) a good example? Define a simple implementation vClasses + associations (if needed) vInterface:  Methods + parameters + return types  Informal description of implementation