1 Events, Actions, and Compositions Somayeh Malakuti, Christoph Bockisch, Mehmet Aksit Software Engineering Group

2 Definition of Runtime Enforcement Nowadays, application software is becoming more and more complex, therefore: it is not possible to detect all the failures of the software before its actual deployment. Runtime Enforcement (RE) Systems: verify the active execution trace of software against formally specified properties. if the properties are violated, RE systems diagnose the cause of failure and take recovery actions accordingly.

3 Obs. Observer Verification Components Application Components Events Observer Diagnosis Components Events Observer Recovery Components Events Observer Verification Components Events Observer Verification Components Events Observer Verification Components Events … … … Elements of a Runtime Enforcement System

4 Compos. Actions Events Compos. Actions Events Compos. Actions Events Compos. Actions Events Compos. Actions Events Compos. Actions Events Actions perform operations and may publish their results as events. Events are typed data primitive types and composite types Composition operators facilitate composition of events and actions based on some constraints. the compositions must be closed with respect to events. Everything boils down to Events, Actions and Compositions

5 AO Implementation of a Runtime Enforcement System Events can be identified via pointcuts primitive pointcuts for identifying primitive events history-based pointcuts/ join point types/ explicit join points for composite events Actions can be defined via advices Compositions advices with pointcuts pointcuts with each other via logical operators advices (aspects) with each other at shared join points

6 Deficiencies in Supporting Events, Actions and Compositions Limited expressive power to define composite event types as a workaround they must be defined as (part of) actions there is no guarantee for side-effect freeness the such actions. Lack of support for side-effect free actions Deficiencies in compositions deficiency in composing events with each other deficiency in composing actions with each other composition constraints are scattered across and tangled with actions. Obs. Observer Verification Components Application Components Events Observer Diagnosis Components Events Observer Recovery Components Events

7 The Extended Compose* to Support Events, Actions and Compositions Filter : Type Application Object Filter : Type Application Object Filter :Type messages The execution and the invocation of application messages are regarded as primitive event types. Filters are means to define composite event types, actions and composition constraints. Two sorts of filters are supported: read-only and read-write. messages

8 Thank you!