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Awareness Requirements John Mylopoulos University of Trento Workshop on “Self- Adaptive Systems” Dagstuhl, Germany October 25-29, 2010. Adaptation is requirements-driven Adaptation takes place when requirements are found to be partially/un-fulfilled.

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Awareness Requirements John Mylopoulos University of Trento Workshop on “Self- Adaptive Systems”

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Awareness requirements john mylopoulos university of trento workshop on self adaptive systems

Awareness Requirements

John Mylopoulos

University of Trento

Workshop on “Self-

Adaptive Systems”

Dagstuhl, Germany

October 25-29, 2010


Awareness requirements john mylopoulos university of trento workshop on self adaptive systems

  • Adaptation is requirements-driven

  • Adaptation takes place when requirements are found to be partially/un-fulfilled.

  • We need some way of talking about “partial fulfillment” …

  • Several ways to go about it, such as:

    • Have relaxed versions of fulfillment, e.g., “as soon as possible”, “as close as possible” (RELAX, [Whittle09])

    • Have fuzzy versions of fulfillment (FLAGS, [Baresi10])

  • This talk offers yet-another way of talking about partial fulfillment of requirements …


Awareness requirements john mylopoulos university of trento workshop on self adaptive systems

  • Awareness

  • Awareness: Consciousness, sentience, ability to sense and respond to the environment.

  • Many types of awareness play a role in the design of software systems (security/process/context/location … )

  • Important topic, not only in Computer Science.

  • In Philosophy, awareness plays a central role in several theories of consciousness. Our notion of awareness requirements draws on the distinction between higher-order awareness (awareness of one’s own mental states) and first-order awareness (awareness of things external) [Rosenthal05].


Awareness requirements john mylopoulos university of trento workshop on self adaptive systems

  • Awareness requirements (awReqs)

  • Refer to other requirements, i.e., Goals/Tasks/Quality Constraints/Domain Assumptions, and run-time properties thereof, i.e., success/failure/performance/consumption/ …

  • Consider

  • r = ‘schedule meeting’, da = ‘always rooms available’

  • r1 = ‘r will be completed within 2hrs’ (delta)

  • r2 = ‘r won’t fail >3 times per year’ (aggregate)

  • r3 = ‘avg r time won’t increase between months’ (trend)

  • r4 = ‘da won’t fail >3 times per year’


Awareness requirements john mylopoulos university of trento workshop on self adaptive systems

  • Awareness vs vanilla requirements

  • Consider

  • r = ‘schedule meeting’

  • r’ = ‘schedule meeting within 2hrs from request’

  • r1 = ‘r will be completed within 2hrs’

  • Semantically, r’ and r1 are (almost) equivalent, yet:

    • Default operationalization for r’ leads to a vanilla design (no monitoring, etc.),

    • The default for r1 leads to a design with full feedback.

  • In other words, reference to other requirements carries with it a modality: “watch this!”, which is what awareness means in the first place (“… ability to sense and respond to the environment.)


Awareness requirements john mylopoulos university of trento workshop on self adaptive systems

Get available rooms

Collect

timetables

By

system

Schedule

meeting

Choose

schedule

By

person

By system

By person

Find rooms

Collect

Requirements

Goal

Softgoal

“# Rooms available for Meetings”

“From how Many”

Good quality schedule

AND

AND

AND

AND

FhM

RfM

+

OR

OR

cp1

-

cp3

OR

cp2

OR

OR

>70% participation

OR

Rooms available

--

Pre/Post-conditions

Schedule

Schedule

Quality

constraint

Domain

assumption

Choice

point

Pre/Post-conditions

Tasks


Awareness requirements john mylopoulos university of trento workshop on self adaptive systems

Get available rooms

Schedule

meeting

Choose

schedule

Collect

timetables

By

system

Collect

Requirements at run-time

FhM=80%

RfM=10

Good quality schedule

AND

AND

AND

AND

OR

OR

Available

rooms

instanceOf

Pre/Post-conditions


Awareness requirements john mylopoulos university of trento workshop on self adaptive systems

  • Object lifetimes: Goals

  • The possible states of each goal instance can be represented by a finite state machine (FSM).

  • Analogous FSMs describe the lifetimes of other requirement objects (QC, DA, T)

Fulfilled

Initiated

Suspended

Failed


Awareness requirements john mylopoulos university of trento workshop on self adaptive systems

  • Reactive Operationalizations

  • Default operationalization for an awareness requirement is a feedback loop consisting of Monitor, Diagnose, Reconcile, Compensate tasks.

M

D

R

C

r


Awareness requirements john mylopoulos university of trento workshop on self adaptive systems

  • Specifications

  • For every assignment of values to each choice point and control parameter, we can generate a specification consisting of tasks, domain assumptions and quality constraints (i.e., functional+non-functional requirements) for the system-to-be.

  • Each such specification constitutes the signature (DNA, ground model1) of a solution/system-to-be that fulfills the requirements we started from.


Awareness requirements john mylopoulos university of trento workshop on self adaptive systems

  • Variability spaces

  • For every requirements problem, we find through goal analysis a variability spaceSpec(ChoicePt, ControlParam) that defines a space of possible behaviours for the adaptive system.

  • In fact, there is a hierarchy of variability spaces as we move from specifications to … to architectures to … to implementations.

  • A basic challenge for this community is to characterize such variability space hierarchies and develop adaptive mechanisms for shifting behaviours within and across layers.


Awareness requirements john mylopoulos university of trento workshop on self adaptive systems

  • From awReqs to feedback loops

  • The task at hand: develop systematic, tool-supported techniques so that, given a set of awareness requirements, we can generate monitoring, diagnostic, reconciliation and compensation functions in a systematic way.

  • We have developed those techniques for monitoring [Souza10], based on past work by Bill Robinson; will base our work on diagnosis and compensation on earlier work by Yiqiao Wang [Wang09a], [Wang09b].

  • The hardest problem ahead of us is designing the reconciliation task of a feedback loop …


Awareness requirements john mylopoulos university of trento workshop on self adaptive systems

See you in


Awareness requirements john mylopoulos university of trento workshop on self adaptive systems

  • References

  • [Baresi10] Baresi, L., Pasquale, L., Spoletini, P., “Fuzzy Goals for Requirements-Driven Adaptation”, 19th International IEEE Conference on Requirements Engineering (RE’10), Sydney Australia, September 2010.

  • [Chung00] Chung, L., Nixon, B., Yu, E., Mylopoulos, J., Non-Functional Requirements in Software Engineering, Kluwer 2000.

  • [Feather98] Feather, M., Fickas, S., van Lamsweerde, A., Pounsard “Reconciling system requirements and runtime behavior”, 9th International Workshop on Software Specification and Design (IWSSD’98), Isobe Japan, April 1998.

  • [Fickas95] S. Fickas, S., Feather, M., “Requirements Monitoring in Dynamic Environments”, 2nd IEEE Int. Symposium on Requirements Engineering (RE’95), York, March 1995.

  • [Finkelstein08] Finkelstein, A., “Requirements Reflection”, workshop presentation, Schloss Dagstuhl seminar 08031: Software Engineering for Self-Adaptive Systems (2008), Wadern, Germany, http://www.dagstuhl.de/08031/

  • [Robinson06] Robinson, W., “A Requirements Monitoring Framework for Enterprise Systems”, Requirements Engineering Journal 11(1), Springer-Verlag, 2006, 17-41.

  • [Robinson08] Robinson, W., “Extended OCL for Goal Monitoring”, Workshop on Modeling Systems with OCL, at MoDELS’07, Berlin, October 2007.


Awareness requirements john mylopoulos university of trento workshop on self adaptive systems

  • References (cont’d)

  • [Robinson09] Robinson, W, Purao, S., “Specifying and Monitoring Interactions and Commitments in Open Business Processes”, IEEE Software, March/April 2009, 2-9.

  • [Rosenthal05] Rosenthal, D., Consciousness and Mind, Oxford University Press, 2005.

  • [Souza09] Silva Souza, V., Mylopoulos, J., “Monitoring and Diagnosing Malicious Attacks with Autonomic Software”, 28th International Conference on Conceptual Modeling (ER’09), Gramado Brazil, November 2009.

  • [Souza10] Silva Souza, V., Lapouchnian, A., Robinson, W., Mylopoulos, J., “Awareness Requirements for Adaptive Systems”, Technical Report, Department of Information Engineering and Computer Science (DISI), University of Trento, September 2010, http://eprints.biblio.unitn.it/archive/00001893/.

  • [Wang09a] Wang, Y., McIlraith, S., Yu, Y., Mylopoulos, J., “Monitoring and Diagnosing Software Requirements”, Journal ofAutomated Software Engineering 16(1), Springer-Verlag, March 2009, 3-35.

  • [Wang09b] Wang, Y., Mylopoulos, J., “Self-repair Through Reconfiguration: A Requirements Engineering Approach”, 24nd IEEE/ACM International Conference on Automated Software Engineering (ASE’09), Auckland, New Zealand, November 2009.

  • [Whittle09] Whittle, J., Sawyer, P., Bencomo, N., and Cheng, B., “RELAX: Incorporating Uncertainty into the Specification of Self-Adaptive Systems,” Proceedings 17th IEEE International Requirements Engineering Conference (RE’09), Atlanta, September 2009.


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