Aspect Assumptions A Retrospective Study of Aspect J

Aspect Assumptions A Retrospective Study of Aspect. J Developers’ Assumptions About Aspect Usage Steffen Zschaler (King’s College London), Awais Rashid (Lancaster University) 23 March, 2011

Motivation • Aspects provide new ways of modularising code • BUT modular reasoning over aspects considered difficult – Some approaches exist • XPIs, Open. Modules, . . . – BUT how do we know if they are good? 23/03/2011 (c) Steffen Zschaler, 2011 2

Motivation (2) • Modular reasoning relies on assumptions and guarantees – Modules provide guarantees if their assumptions are met • So what types of assumptions do aspect developers make? 23/03/2011 (c) Steffen Zschaler, 2011 3

Using Assumption Types • Assumption elicitation – Use catalogue as “check list” in inspections – Extract patterns that may be used to identify certain assumption types (semi-)automatically • Assumption verification – Provide specification template for each type • Type-specific assumption specifiers • Code improvement – Some assumptions really are indications of bugs 23/03/2011 (c) Steffen Zschaler, 2011 4

Study Design Studied 3 open-source AOP projects 1. Manually identified assumptions (explicit & implicit) 2. Validated findings with original developers 3. Manually classified into types 4. Validated classification with original developers 23/03/2011 (c) Steffen Zschaler, 2011 5

Selected Projects Mobile Media Health Watcher Glassbox Academic project on an industrial basis Industrial project Aspects specifically developed; Some generalisation for reusability Aspects developed for reuse Mostly static crosscutting Mostly dynamic crosscutting Refactored from an OO system Evolved from an OO system AOP from scratch 23/03/2011 (c) Steffen Zschaler, 2011 6

What’s in an Assumption? System S Weaving context wctx(A) 23/03/2011 Aspect A Δ (c) Steffen Zschaler, 2011 7

Assumption Types Aspect–Aspect Coordination Inter-Aspect Assumptions Inter-Advice Deployment ITDs Sub-Aspect Structure Precedence Super-Aspect Structure Wormhole Inter-Process Advice Execution Sequence Aspect–Base Coordination Synchronisation Managed by Context 23/03/2011 Monitor Sharing Architecture Communication (c) Steffen Zschaler, 2011 Coding Patterns Data Code Advised Code Called 8

Threats to Validity • Limited number of projects – Found and classified 183 assumptions – Cover a range of different AOP project characteristics – New projects may still require new classes to be added • Manual identification and clustering – May have misinterpreted / misunderstood – Constant checks and feedback from original developers • All Aspect. J – May be relevant for other modularisation techniques • Further research needed – Aspect. J most used, though 23/03/2011 (c) Steffen Zschaler, 2011 9

Future Work • Simplify assumption specification – Formalisation templates – Custom language concepts • Experiments on assumption elicitation • Aspect. J anti-patterns • Assumptions in other modularisation techniques 23/03/2011 (c) Steffen Zschaler, 2011 10