User Requirements Notation (URN )

SCHOOL OF INFORMATION TECHNOLOGY AND ENGINEERING

UNIVERSITY OF OTTAWA, CANADA

Daniel AmyotQ18/17 (URN) Rapporteur

[email protected]

User Requirements Notation (URN )

Workshop on "Framework and scope of formal languages", Geneva, March 2, 2002 2

Objectives

Brief overview of URN Goal-oriented Requirement Language (GRL),

Use Case Maps (UCMs), and their relationships

Connections between URN and several languages from ITU and OMG

Several Challenges


Need improvement to cope with new realities of complex, dynamic, and evolving systems

Common design and standardisation methodologies already use scenarios

Requirements and Service Description

Stage 1

Message Sequence

Information

Stage 2

Protocols,Procedures,Behaviour

Stage 3

SDL orUML Statechart

diagrams

MSC orUML interaction

diagrams

Informal requirements?Use Cases?

URN!

Motivation for URN


URN - Initial Objectives

Focus on early stages of design, with scenarios Capture user requirements when little design detail is

available No messages, components, or component states

required Reusability of scenarios and allocation to components Dynamic refinement capabilities Modelling of agent systems, early performance

analysis, and early detection of undesirable interactions


URN - Additional Objectives

Express, analyse and deal with non-functional requirements (NFRs)

Express the relationship between business objectives/goals and system requirements

Capture reusable analysis (argumentation) and design knowledge (patterns) for addressing non-functional requirements

Connect to other ITU-T languages (and to UML)


Current Proposal for URN

Draft documents for Z.150, Z.151, Z.152– http://www.UseCaseMaps.org/urn/

Combined use of two complementary notations:– Goal-oriented Requirement Language (GRL) for

NFRs (http://www.cs.toronto.edu/km/GRL/)– Use Case Maps (UCM) for Functional

Requirements (http://www.UseCaseMaps.org/) Create ITU-T standard by end of 2003

(Z.150-153)


GRL in a Nutshell

Goal-oriented Requirement Language — a graphical notation that allows reasoning about (non-functional) requirements

GRL is concerned with intentional elements, actors, and their relationships

Intentional elements model the “why” aspect — objectives, alternatives, as well as decision rationale and criteria — but not operational details

GRL satisfies most of URN’s additional objectives


Basic GRL Notation

Means-End Goal

Decomposition(AND)Correlation

(side-effect)

Belief

Argumentation

Task

Make..

Contribution

Softgoal

PasswordCardkey Biometrics

Identification

Cost ofTerminal

Biometrics is noregular off-the-shelf

technology

AccessAuthorization Encryption

Authentication

Security ofHost

Security ofTerminal

SystemSecurity


Evaluations with GRL

..

PasswordCardkey Biometrics

Identification

Cost ofTerminal

Biometrics is noregular off-the-shelf

technology

AccessAuthorization Encryption

Authentication

Satisficed

Weakly Satisficed

Undecided

Weakly Denied

Denied

Security ofHost

Security ofTerminal

SystemSecurity


UCMs in a Nutshell

Use Case Maps – a graphical scenario notation for describing causal relationships between responsibilities

Scenario elements may (optionally) be linked to components

The intent of UCMs is to facilitate the integration and reusability of scenarios, and to guide the design of high level architectures and detailed scenarios from requirements

UCMs satisfy most initial URN requirements


Component

StartPoint

End Point

Responsibility

Stub

AND-Fork

Pool

a) Root UCM

Slot

b) Biometrics Plug-In c) PassWord Plug-in

Timer

OR-Fork


GRL - UCM Relationship

Goal-based approach– Focuses on answering “why” questions– Addresses functional and non-functional

requirements Scenario-based approach

– Focuses on answering “what” questions Goals are operationalized into tasks and

tasks are elaborated in (mapped to) UCM scenarios– Focuses on answering “how” questions


From UCM Requirements to More Detailed Design Models

Requires:– Path Data Model (global

Booleans variables)– Scenario Definitions– Path Traversal Mechanism– Mapping Rules (MSC, UML,

TTCN, LQN, LOTOS...)


Informal Requirements,

Textual Use Cases

URN — OMG/SG17 Puzzle

UCMs link to operationalizations

(tasks) in GRL models

Structural Diagrams

SDL, or UML Class, Object, Component, &

Deployment Diagrams

Testing and Performance Languages

TTCN, LQN, ...

Behavioral DiagramsMSC/SDL, or UML

Sequence, Collabor., & Statechart Diagrams

UCMs represent visually use cases in terms of causal

responsibilities

UCMs provide a framework for

making high level and detailed

design decisions

UCMs visually associate

behavior with structure at the

system level

?

?UML Use Case

Diagram & Activity Diagram

URN-NFR/GRLGoals, non-functional requirements, alterna-

tives, rationales

URN-FR / UCMsSuperimpose visually system level behavior

onto structures of abstract components


Several Challenges (I)

Degree of formalisation– Qualitative/quantitative GRL evaluations?– UCM path traversal algorithms?– Reasoning in presence of looseness,

incompleteness, inconsistencies? Formalisation of languages

– BNF? Graphical grammar? XML & schemas?

– Layout information?


Several Challenges (II) Extensibility and Adaptability

– UML Profiles? Connections to other languages

– Traceability, transformations, meta-model? Methodologies

– What subsets of languages make sense together?

– Do methodologies drive the evolution of standard languages?

– Who are the stakeholders?

Documents

User Requirements Notation (URN )