UML Profile for Schedulability, Performance and Time (UML-SPT)

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5007437 Web Services: Architecture, Concepts and Standards Dr. José Merseguer

UML Profile for Schedulability,

Performance and Time (UML-SPT)

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Part III: UML SPT

1st step: Model the system using UML.

2nd step: Annotate performance characteristics using the

SPT Profile.

3rd step: Translate the UML-SPT diagrams into Petri nets.

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UML-SPT: Introduction

January 2005, OMG standard Profile.

A Profile is an extension to the

semantics

of UML that conforms to

the meta-model.

¾

A specialization, inheriting from the UML standard.

¾

A domain-specific interpretation

e.g. UML Profile for Enterprise Application Integration; for Distributed

Object Computing; Testing Profile; for Software Radio, …

It should use only standard extension mechanisms:

stereotypes,

tag values, constraints

¾

Additional semantic constraints cannot contradict the general UML

semantics.

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Specializing UML: Stereotypes and tagged values

A stereotype is a specialization of a UML entity, implying a certain

interpretation.

Integer

MyClockClass

SetTime()

«clock»

{resolution = 500 ns}

«clock» Stereotype of Class

with added semantics:

an active counter whose value

changes synchronously with

the progress of physical time

...a stereotype can extend the class

Tagged value associated

with the «clock» stereotype:

tag = value

value has a type such as:

integer ‘sec’|‘ms’|‘ns’

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UML-SPT: General Principles

Ability to specify quantitative information directly in UML models

¾

Key to quantitative analysis and predictive modeling.

Flexibility:

¾

Users can model their systems using modeling approaches and styles of their

own choosing

Æ

not hamper design

.

¾

Open

to existing and new analysis techniques.

Facilitate the use of analysis methods

¾

Eliminate the need for a

deep understanding

of analysis methods.

¾

As much as possible,

automate

the generation of analysis models and the

analysis process itself.

Using analysis results for:

¾

predicting

system characteristics (detect problems early).

¾

analyze

existing system

(sizing, capacity planning).

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UML-SPT: Structure

<<profile>>

SAprofile

<<profile>>

PAprofile

<<profile>>

RTresourceModeling

<<profile>>

RTtimeModelling

Analysis Models

General Resource Modeling Framework

<<import>>

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UML-SPT: Structure…

Schedulability analysis

: applied to

hard real-time

systems to

find a schedule that will allow to meet all the system’s deadlines.

Performance analysis

: applied to

soft-real time

systems with

stochastic characteristics. Queuing based methods are used for

mean value analysis and/or for checking if soft deadlines are met

by the system.

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UML-SPT: Resource Modeling

Resource:

¾

Hardware or software.

¾

An element whose

service capacity is limited

, directly or indirectly, by

the finite capacities of the underlying physical elements.

Resources offer services that have QoS attributes

Resource R ... set of services Si ... QoS of Si

Quality of Service (QoS):

¾

A specification (usually quantitative) of

how well

a particular service

is (to be) performed.

¾

e.g. throughput, capacity, response time

The specification of a model element can include:

¾

Offered QoS

: the QoS that it provides to its clients.

¾

Required QoS

: the QoS it requires from other components to support

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UML-SPT: Resource Modeling …

Resources have services that have QoS characteristics

Resources and services have instances, and QoS has value

Descriptor

Instance

1..n

0..n

+type

1..n

0..n

/

0..n

+offeredQoS

0..n

/

0..n

ResourceInstance

Resource

1..n

0..n

+type

1..n

+instance

0..n

ResourceService

ResourceServiceInstance

0..n

+type

1 +instance

0..n

1..n

+offeredService 1..n

l

1..n

QoScharacteristic

0..n

1 QoSvalue

0..n

+offeredQoS

0..n

1 0..n

+type

1 +instance

0..n

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UML-SPT: Time Modeling

ResourceInstance (from CoreResourceModel) Timeout (from TimedEvents) Timer isPeriodic : Boolean 1 0..n 1 +generatedTimeouts 0..n ClockInterrupt (from TimedEvents) TimeInterval (from TimeModel) Clock 1 0..n +offset 1 0..n 1 0..n +accuracy 1 0..n 0..n 1 +generatedInt errupts _0..n 1 TimeValue (from TimeModel) TimingMec hanism stability drift skew set(time : TimeValue) get() : TimeValue reset() start() pause() 1 0..n +resolution 1 0..n 0..n 1 0..n +referenceClock 1 1 0..n +currentValue 1 0..n 1 0..n +max imalValue 1 0..n TimeValue (from TimeModel) 1 0..n +duration 1 0..n TimedEvent (from TimedEvents) 1..n +times tamp 1..n 1 +origin 1

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UML-SPT: Performance Modeling

<<deploys>>

ClosedWorkload

population

externalDelay

OpenWorkload

oc currencePat tern

PResource

utilization

schedulingPolicy

throughput

PProcessingResource

processingRate

contextSwitchTime

priorityRange

isPreemptible

PerformanceContext

1..n

0.. n

1..n

0.. n

W orkload

responseTime

priority

1..n

1 1..n

1 PStep

probabilty

repetition

delay

operations

interval

executionTime

0..n

+successor

0..n

+predecessor 0..n

PScenario

hostExecutionDemand

responseTime

0..n

+resource

0..n

0..1

0..n

+host 0..1

0..n

1..n

1 1..n

1

1 1..n

1..n

1

1 +root

₁

1 PPassiveResource

waitingTime

responseTime

capacity

accessTime

{ordered}

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UML-SPT: Performance Modeling …

Provides the

concepts

to annotate the UML models with

performance

characteristics

.

Performance context

¾

Specify one or more scenarios that are used to explore various dynamic

situations involving a set of resources.

Scenario

¾

Has the attribute

responseTime

.

¾

In our approach a SD is a scenario.

¾

QoS requirements are placed on scenarios.

¾

a Scenario is a sequence of Steps (predecessor/successor)

Scenario has a first Step, which is stereotyped with a workload definition

¾

PAopenLoad (stream of requests) with tags for an arrival process (such as

Poisson).

¾

PAclosedLoad

(users or jobs cycling the scenario) with tags for a population

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UML-SPT: Performance Modeling …

Step

¾

a Step inherits from Scenario, so it can be refined as a sub-scenario

¾

Has demand,

PAdemand

tag gives the CPU demand.

¾

PAextOp

tag defines operations such as file operations, that are not

modeled in the UML model but are needed for the performance

model (

completions

)

¾

PAdelay

specifies a delay that may be part of the operation (a “sleep”

time)

¾

a Step has predecessors (giving AND fork and join)

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UML-SPT: Tags for specifying performance values

A complex structured string with the following format

<performance-value>::=<kind-of-value> , <modifier> , <time-value>

where:

<kind-of-value> ::= ‘req’ | ‘assm’ | ‘pred’ | ‘msr’

required, assumed, predicted, measured

<modifier> ::= ‘mean’ | ‘sigma’ | ‘kth-mom’, <Integer> |‘max’

| ‘percentile’ <Real> | ‘dist’

Examples:

¾

measured CPU demand of a scenario step:

{PAdemand = (‘msr’, ‘mean’, (20, ‘ms’))}

¾

scenario response time: required and predicted (variable $RT is a placeholder

for a performance model result)

{PArespTime = (‘req’, ‘mean’, (10, ‘sec’))

PArespTime = (‘pred’, ‘mean’, $RT)}

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UML-SPT: time value

Tag type RTtimeValue can represent a wide variety of types

related to time, such as:

¾

12:04

(time of day)

¾

5.3, ‘ms’

(time interval)

¾

2000/10/27

(date)

¾

Wed

(day of week)

¾

$x, ‘ms’

(parameterized value with name $x)

¾

‘poisson’, 5.4, ‘sec’

(time value with a Poisson distribution)

¾

‘histogram’ 0, 0.28 1, 0.44 2, 0.28, 3, ‘ms’

P=0.28

P=0.44

P=0.28

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UML-SPT: The POP3 example

{PAprob=0.8}

<<PAStep>>

{PAprob=0.2}

<<PAStep>>

UserMainState

fsClient

psClient

DO: Thinking

/ CH.check_mail

/ CH.exit_exec

Performance context

Scenario probability

Step probability

{PAprob=0.2}

{PAprob=0.8}

<<PAcontext>>

<<PAscenario>>

Send

Mail

Check

Mail

User

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UML-SPT: The POP3 example

Scenario

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UML-SPT: The POP3 example

Update

unlock_maildrop

Listening on

TCP port 110

read_message

Sending

DO: Authorization

Authorization

quit

dele

/ send_ok

list / send_ok

Transaction

psPOP3Server

/ send_greeting

open_tcp_connection

_message

/ send_attach−

retr

_message

/ send_text−

/ send_ok

{PAprob=$P}

<<PAStep>>

{PAprob=$Q}

<<PAStep>>

<<PAClosedLoad>>

{PApopulation=1}

System load

Step probability

Resource demand

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UML-SPT: The POP3 example

Step probability

Resource demand

<<PAStep>>

{PAprob=0.2,

PAdemand=(’ass’,’dist’,

((’exponential’,3),’s.))}’

{PAprob=0.1}

<<PAStep>>

{PAprob=0.8,

PAdemand=(’ass’,’dist’,

((’exponential’,1),’s.’))}

<<PAStep>>

{PAprob=0.8,

PAdemand=(’ass’,’dist’,

((’exponential’,2),’s.’))}

{PAprob=0.9}

<<PAStep>>

{PAprob=0.2,

PAdemand=(’ass’,’dist’,

((’exponential’,5),’s.’))}

ClientHost

Username

Wait4User

ERR

OK

[user found]

Wait4Password

Password

ERR

[user not found]

[matches]

[doesn’t match]

LockMaildrop

OK

ERR

[already locked]

[not locked]

Look4User

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UML-SPT: The POP3 example

{PAprob=$P}

<<PAStep>>

<<PAClosedLoad>>

{PApopulation=$N}

{PAprob=$Q}

<<PAStep>>

{PAprob=$S}

<<PAStep>>

{PAprob=$R}

<<PAStep>>

Waiting4Entry

check_mail

send_open_tcp_connection

Authentication

send_username

CheckPassword

send_password

greeting

ok

err

RetrieveMessage

send_retr

Quitting

send_quit

err

DeleteMessage

send_dele

text_message

attach_message

exit_exec

Greeting

ok[messages_left]

ok[not messages_left]

ok

CheckMessages

send_list

ok[new]

ok[not new]

ok

psMClient

fsMClient

Step probability

Resource demand

System load

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UML-SPT: The POP3 example

m:mailClient

:clientHost

s:ServerHost

:Internet

<<PAresource>>

:serverHost

<<PAspeed>>

{(’ass’,(100,Kbps))}

Network speed

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UML-SPT: General Model Processing Framework

Software Domain

_{Schedulability/}

UML Profile for Schedulability, Performance and Time (UML-SPT)