Deriving Operational Software Specification from System

Goals

Xin BaiEEL 5881 Course

Fall, 2003

Reference Paper

“Deriving Operational Software Specification from System Goals” November 2002, Proceedings of the tenth

ACM SIGSOFT symposium on Foundations of software engineering

Content

Introduction Goal-Oriented Elaboration of Require

ments Semantics of Operationalization Operationalization Patterns Analysis

Introduction Lots of techniques and tools for

specification analysis Algorithmic model checking, Deductive

verification etc. Building formal specifications for

complex software is not easy Translate natural language statements to

some formal language To be elaborated, structured, interrelated

and negotiated

Introduction

Goal-oriented requirements engineering The use of goals for requirements

elicitation, elaboration, organization, specification, analysis, negotiation, assignment, documentation and evolution.

Introduction

Goals Objectives the system under consideratio

n must achieve E.g. “safe transportation” and “reverse th

rust enabled when wheels pulse on” Achieving goals require the cooperation

of multiple agents (humans, devices or software)

Introduction

Goal refinement To decompose a goal into subgoals so th

at each subgoal requires the cooperation of fewer agents

Stops when goals can be assigned as responsibility of single agents

Goal-oriented elaboration of requirements An application model is composed of f

our submodels: Goal model Object model Agent model Operation model

The goal model The various objectives the system

should meet are defined in this model

The goal model

Temporal operators

The goal model

The goal model A sample

The object model

Defines the domain entities, relationships and attributes

A sample

The agent model

Defines the responsibilities and interfaces of the various agents

A sample

The operation model Defines the various services to be provided

by agents Domain pre/post conditions

Capture the elementary state transitions defined by operation applications in the domain

Required pre/post/trigger conditions Capture additional strengthenings to ensure tha

t the goals are met

The operation model A required preconditions

Captures a permission to perform the operation when the condition is true

A required trigger condition Captures an obligation to perform the operation

when the condition becomes true provided the domain precondition is true

A required postcondition Captures an additional condition that must hold

after any application of the operation

The operation model Difference between domain and

required conditions Domain conditions describe what an

application of the operation means in the domain without any prescription as to when the operation must be applied and when it may not be applied.

The operation model A sample for domain conditions

The operation model A sample for required conditions

Semantics of operationalization Functional goals need to be operation

alized into specifications of services the agents should provide to meet them

Operationalization is a process that maps declarative property specifications to operational specifications satisfying them

Semantics of operationalization It takes the form of a set of

operations specified by domain and required pre, post- and trigger conditions.

Semantics of operationalization Correctness of goal operationalizatio

n Completeness Consistency minimality

Operationalization patterns A pattern-based technique for operati

onalizing goals, specified in real-time linear temporal logic (RT-LTL), into operations specified by pre-, post- and trigger conditions

Operationalization patterns An operationalization pattern is an ab

stract AND-operationalization link between a goal specification pattern in RT-LTL and a set of required pre-, trigger and postcondition specification patterns that operationalize the root correctly.

Operationalization patterns The Immediate Achieve pattern

Operationalization patterns The Bounded Achieve pattern

Operationalization patterns The “InBetween” Invariance patter

n

A taxonomy of goal patterns

Operationalization patterns In every but very rare cases, the

goals match one of the general patterns in the previous taxonomy diagram

Not complete, could be enriched with additional goal patterns

Analysis

Benefits Abstraction from formal details Completeness assurance Guidance in writing operational

specifications Goal mining from operational

specifications

Thank you!