ModellingClass T04

Requirements and Use CasesReferences:• http://www.sysml.org• http://www.omg.org

UML and SysML

2Modelação

UML – An overview…

3Modelação

SysML – An overview…

4Modelação

A Context Diagram(example for a HybridSUV system)

Modelação 5

ibd Automotiv eDomain [Automotiv eDomain] ...

driv er :Driv er

:Passenger

:Maintainer

«diagramDescription»

version="0.1"description="Initial concept to identify top level domain entities"reference="Ops Concept Description"completeness="partial. Does not include gas pump and other external interfaces."

HSUV :HybridSUV

«BlockProperty»

v ehicleCargo :Baggage

«BlockProperty»

«BlockProperty»

driv ingConditions :Env ironment

object :ExternalObject

«BlockProperty»road :Road

«BlockProperty»

weather :Weather

«BlockProperty»

Use Cases• Use cases describes an interaction between the system and other

external entity (an actor).

• The description must be provided from the point of view of the actor!

Therefore it describes "who" can do or is affected by "what" with or

from the system.

• The use case technique is used to elicit functional requirements by

relating them with usage/behavioral scenarios.

• In a document requirements the use cases can be presented before

the lists of requirements, as they can provide good glimpses…

• Use cases are also useful to make the bridge between the

requirements documenting and the modeling of the detailed

systems’ behavior

Modelação 6

High level use cases

Modelação 7

uc HSUVUseCases [TopLev elUseCases]

HybridSUV

Operate the v ehicle

Registered Owner

Insure the v ehicle

Register the v ehicle

Insurance Company

Department of Motor Vehicles

Maintainer

Maintain the v ehicle

Driv er

High level use cases

Modelação 8

uc HSUVUseCases [TopLev elUseCases]

HybridSUV

Operate the v ehicle

Registered Owner

Insure the v ehicle

Register the v ehicle

Insurance Company

Department of Motor Vehicles

Maintainer

Maintain the v ehicle

Driv er

Actors

Use Cases

uc HSUVUseCases [TopLev elUseCases]

HybridSUV

Operate the v ehicle

Registered Owner

Insure the v ehicle

Register the v ehicle

Insurance Company

Department of Motor Vehicles

Maintainer

Maintain the v ehicle

Driv er

High level use cases

Modelação 9

These actors might be the same object, but conceptually we must consider them independents

Modelação 10

Casos de Uso: Example of a templateName UC-8: Search

Summary All occurrences of a search term are replaced with replacement text.

Rationale While editing a document, many users find that there is text somewhere in the file being edited that needs to be replaced, but searching for it manually by looking through the entire document is time-consuming and ineffective. The search-and-replace function allows the user to find it automatically and replace it with specified text. Sometimes this term is repeated in many places and needs to be replaced. Other times, only the first occurrence should be replaced. The user may also wish to simply find the location of that text without replacing it.

Users All users

Preconditions A document is loaded and being edited.

Basic Course of Events

1. The user indicates that the software is to perform a search-and-replace in the document.2. The software responds by requesting the search term and the replacement text.3. The user inputs the search term and replacement text and indicates that all occurrences are to

be replaced.4. The software replaces all occurrences of the search term with the replacement text.

Alternative Paths

1. In step 3, the user indicates that only the first occurrence is to be replaced. In this case, the software finds the first occurrence of the search term in the document being edited and replaces it with the replacement text. The postcondition state is identical, except only the first occurrence is replaced, and the replacement text is highlighted.

2. In step 3, the user indicates that the software is only to search and not replace, and does not specify replacement text. In this case, the software highlights the first occurrence of the search term and the use case ends.

3. The user may decide to abort the search-and-replace operation at any time during steps 1, 2 or 3. In this case, the software returns to the precondition state.

Postconditions All occurrences of the search term have been replaced with the replacement text.

Driver’s use cases

Modelação 11

uc HSUVUseCases [Operational Use Cases]

HybridSUV

Driv er Accelerate

Steer

Brake

Park

Start the v ehicle

Driv e the v ehicle

«include»

«include»

«include»

«extend»

«include»

Driver’s use cases

Modelação 12

uc HSUVUseCases [Operational Use Cases]

HybridSUV

Driv er Accelerate

Steer

Brake

Park

Start the v ehicle

Driv e the v ehicle

«include»

«include»

«include»

«extend»

«include»

Driver’s use cases

Modelação 13

uc HSUVUseCases [Operational Use Cases]

HybridSUV

Driv er Accelerate

Steer

Brake

Park

Start the v ehicle

Driv e the v ehicle

«include»

«include»

«include»

«extend»

«include»

Complex use cases can be detailed in other diagrams…

SysML – An overview…

14Modelação

Requirements and Stakeholders

• Requirements– A requirement specifies a capability or condition that must (or

should) be satisfied.. A requirement may specify a function that a system must perform or a performance condition that a system must satisfy. Requirements are used to establish a contract between the customer (or other stakeholder) and those responsible for designing and implementing the system.

• Stakeholders– Anybody involved in the system’s lifecycle (analysis, design,

development, maintenance, …)– Anybody else who, directly or indirectly, may impose

requirements for the system (business owner, user, …)

Modelação 15

Types of requirements

Modelação 16

• Functional Requirements (FR)– The specification of a function of the system or its components.

– It must refer a behaviour of the system!

• Non-Functional Requirements (NFR)– It must refer how the system must behave.

– Examples of non-functional requirements: Performance; Scalability; Availability; Reliability; Maintainability; Serviceability; Security; Regulatory; Manageability; Usability; Interoperability

Requirements specification

Modelação 17

req HSUVSpecification [HSUV Specification]

HSUVSpecification

(from HSUVModel)

Eco-Friendliness

Braking

FuelEconomy

OffRoadCapability

Acceleration

Ergonomics

Qualification

Safety Test

PerformanceCapacity

Cargo Capacity

Passenger Capacity

Fuel Capacity

Emissions

Requirements derivation

Modelação 18

req HSUVRequirements [Requirement Deriv ation] ...

«rationale»

Power delivery must happen by coordinated control of gas and electricmotors.

«problem»

Power needed for acceleration, off-road performance & cargo capacity conflicts with fuel economy

PowerSourceManagement

Fuel Capacity

(from HSUVSpecification)

OffRoadCapability

(from HSUVSpecification)

Acceleration

(from HSUVSpecification)

Cargo Capacity

(from HSUVSpecification)

FuelEconomy

(from HSUVSpecification)

Range

RegenerativeBraking

Braking

(from HSUVSpecification)

«RefinedBy»

HSUVStructure::HSUV.HSUVOperationalStates

Power

«derive»

«derive»

«derive» «derive»

«derive»«derive»

«derive»

«derive»«derive»

Requirements in the Enterprise Architect…

Modelação 19

VERY IMPORTANT:

Be aware that EA tool supports

requirements diagrams as

formal SysML Requirements

Diagrams

or as

informal requirements diagrams

as extensions to UML

Requirements containment

The containment (cross hair) relationship refers to the practice of decomposing a complex requirement into simpler, single requirements.

Modelação 20

Copy relationship

A Copy relationship is a dependency between a supplier requirement and a client requirement that specifies that the text of the client requirement is a read-only copy of the text of the supplier requirement.

A Copy dependency created between two requirements maintains a master/slave relationship between the two elements for the purpose of requirements re-use in different contexts. When a Copy dependency exists between two requirements, the requirement text of the client requirement is a read-only copy of the requirement text of the requirement at the supplier end of the dependency.

Modelação 21

Callout relationship (notes)

A callout notation can be used to represent derive, satisfy, verify, refine, copy, and trace relationships…

Modelação 22

DeriveReqt relationship

Modelação 23

A DeriveReqt relationship is a dependency between two requirements in which a client requirement can be derived from the supplier requirement.

For example, a system requirement may be derived from a business need, or lower-level requirements may be derived from a system requirement.

As with other dependencies, the arrow direction points from the derived (client) requirement to the (supplier) requirement from which it is derived.

Verify relationship

A Verify relationship is a dependency between a requirement and a test case or other model element that can determine whether a system fulfills the requirement.

Modelação 24

Satisfy relationship

A Satisfy relationship is a dependency between a requirement and a model element that fulfills the requirement.

Modelação 25

Refine relationship

The refine requirement relationship can be used to describe how a model element or set of elements can be used to further refine a requirement.

For example, a use case or activity diagram may be used to refine a text-based functional requirement. Alternatively, it may be used to show how a text-based requirement refines a model element. In this case, some elaborated text could be used to refine a less fine-grained model element

Modelação 26

Trace relationship

A generic trace requirement relationship provides a general-purpose relationship between a requirement and any other model element. The semantics of trace include no real constraints and therefore are quite weak.

As a result, it is recommended that the trace relationship not be used in conjunction with the other requirements relationship...

Modelação 27

Relating requirements with other elements

Modelação 28

Use Cases

Modelação 29

Use cases and requirements

Modelação 30

Traceability

Traceability Diagrams

Modelação 31

Relationship Matrix

A fundamental technique in modelling to relate decisions with their origin or implications

Traceability in the Enterprise Architect tool