Overview of iStar 2.0 Language Guide - UFPEif716/arquivos20161/Overview-iStar-20... · 2018. 9. 5. · 3 iStar 2.0 Context iStar “1.0” released in 1995 (Eric Yu’s PhD Thesis)

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Overview of iStar 2.0 Language Guide

This presentation is based on:

Dalpiaz, F., Franch, X. and Horkoff, J. (2016) iStar 2.0 language guide. arXiv preprint arXiv:1605.07767.

Eric, S. Y. (1995). Modelling strategic relationships for process reengineering. PhD Thesis. Department of Computer Science, University of Toronto.

Camilo C. Almendra

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Summary

Context and Motivation Language guide for version 2.0 Comparison with original version Conclusions

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iStar 2.0

Context iStar “1.0” released in 1995 (Eric Yu’s PhD Thesis) Highly active research community on GORE and iStar Too much diversity of extensions and variations (Horkoff

et al. 2014) Problems

Difficulty to learn and teach Lack of core reference for professional usage Fragmentation of tool development

Horkoff, J., Li, T., Li, F. L., Salnitri, M., Cardoso, E., Giorgini, P., ... & Pimentel, J. (2014). Taking goal models downstream: a systematic roadmap. In Research Challenges in Information Science (RCIS), IEEE Eighth International Conference on.

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iStar 2.0 Initiative

Purpose Establish core fundamental concepts and rules Keep language open to tailoring Foster framework usage outside research community

Timeline Oct’14: initial community meeting Jun’15: standardization committee was formed Aug’15, Oct’15: initial draft discussions Dec’15: preliminary version discussions Mar’16: final version released Jun’16: minor improvements

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iStar 2.0 Language Guide

Standardization process Based on Eric Yu’s thesis and seminal paper Discussions with experts to identify core improvements Focus on concepts and relationships

Out of scope Ontological definition of constructs Visual notation improvements Methodological issues

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iStar 2.0 Language Guide

Structure Actor and actor types Actor association links Intentional elements Social dependencies Intentional element links Model views Metamodel

Differences from original version will be highlighted

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Actors and Actor Types

Actors Active, autonomous entities that aim at

achieving their goals by exercising their know-how, in collaboration with other actors

Generic Used when type is not relevant (yet)

Role Abstract characterization of the behavior of a

social actor Agent

Actor with concrete, physical manifestations

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Position actor (original version) Intermediary abstraction

between a role and an agent Set of roles typically played by

one agent Agent occupies a Position Position covers a Role

Removed from 2.0 Position can be expressed using

actor association links (see next)

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Actor Boundary Container for actor’s intentional elements

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Actor Association Links

Association Links Binary links from a actor (source) to another single

actor (target) is-a

Represents specialization/generalization Only Roles can specialize other Roles Only Generic actors can specialize other Generic

actors Agents can not be specialized (they are concrete)

participates-in Any other kind of association When source and target are same type, it means

“part-of” When target is a Role, it means actor “plays” the

role.

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Actor Association LinksRepresenting “Position” actor from original version using iStar 2.0

participates-inparticipates-in

participate

s-in

Physician

occupies

playscovers

part of

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Intentional Elements

Goal State of affairs that the actor wants to achieve

Quality (softgoal in original) Attribute for which an actor desires some level of achievement

Task Represents actions that an actor wants to be executed

Resource Physical or informational entity that the actor requires in order to

perform a task

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Social Dependencies

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Dependency Arguments

depender Actor that depends for something (the dependum) to be provided

dependerElmt Intentional element within the depender’s actor boundary where the

dependency starts from, which explains why the dependency exists It can be ommited

dependum Intentional element that is the object of the dependency

dependee Actor that should provide the dependum

dependeeElmt Intentional element that explains how the dependee intends to provide the

dependum It can be ommited

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Social Dependencies

dependeeElmt ommitted or not yet defined

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Dependencies Semantics

Types of dependum Goal

Dependee is expected to achieve the goal, and is free to choose how Quality

Dependee is expected to sufficiently satisfy the quality, and is free to choose how

Task Dependee is expected to execute the task in a prescribed way

Resource Dependee is expected to make the resource available to the depender

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Intentional Element Links

Purpose Intentional elements from an actor’s intentionality can be related in four

different ways Each type of links represents a kind of influence

Refinement Used for Goals and Tasks, it provided a way to link them hierarchicaly

Needed-by Only used from Resources to Tasks, to indicate an actor needs a resource to

execute the task Contribution

It provided ways to represent effects of intentional elements on Qualities Qualification

It links Qualities to intentional elements to express desired attributes to be applied during goal achievements, task execution or resource provision

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iStar 2.0 intentional elements possible relationships

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Original versus 2.0

Refinement

Needed-by

Contribution

Contribution

Refinement

Refinement

Qualification

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Refinements

AND-refinement: all sub-goals achieved/ sub-tasks performed

OR-refinement: At least one sub-goal achieved or sub-task performed

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Needed-by

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Contributions

Weakly Satisfies

Sufficiently Satisfies

Sufficiently Denies

Weakly Denies

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Contributions (Softgoal-Task Link in original version)

Eric Yu’s original version examplifies positive and negative contributions using ‘+’ and ‘-’ signals.

It’s out of scope of his thesis to indicate a definitive framework/notation.

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Qualification● It provides a more powerful representation of influences of

quality criteria in dependencies and intentional elements

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Model Views

Strategic Dependency (SD)

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Model Views

Strategic Rationale (SR)

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Model Views

Hybrid SD/SR (new!)

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Metamodel and Rules

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Metamodel and Rules Integrity constraints (some of them)

The is-a relationship applies only between pairs of roles or pairs of actors

There should be no is-a cycles There should be no participates-in cycles A pair of actors can be linked by at most one actor link: it is not

possible to connect two actors via both is-a and participates-in; In a dependency D, if the dependerElmt x exists, then the actor that

wants x is the same actor that is D’s depender ...

More rules are stated in the guide Rules promotes a more uniform usage of language

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Conclusions

iStar 2.0 Language Guide provides a more structured and uniform description of language constructs and rules Ease of learning and teaching Common baseline for extensions proposals

Relationships’ symbols overload is reduced Task Decomposition Links are divided into Refinements, Needed-

by and Qualification Means -ends Links are divided into Refinements and Contribution

Rules of association are established This eases dissemination of good practices and producing

compatible models between different practitioners Language still lacks a extension mechanism

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Overview of iStar 2.0 Language Guide - UFPEif716/arquivos20161/Overview-iStar-20... · 2018. 9. 5. · 3 iStar 2.0 Context iStar “1.0” released in 1995 (Eric Yu’s PhD Thesis)