UML sơ đồ tương tác

A combined fragment is defined by an interaction operator and corresponding interaction operands..  The interaction operator alt means that the combined fragment represents a choice or

UML Sơ đồ tương tác

GV : TS Trương Quốc Định

Sequence Diagrams 2

Sequence Diagrams 3

Interaction Diagrams (Cont.)

 The purpose of Interaction diagrams is to:

 Model interactions between objects

 Assist in understanding how a system (a use case) actually works

 Verify that a use case description can be supported by the existing classes

 Identify responsibilities/operations and assign them to classes

Sequence Diagrams 4

Interaction Diagrams (Cont.)

Sequence Diagrams 5

A First Look at Sequence Diagrams

 Illustrates how objects interacts with each other

 Emphasizes time ordering of messages

 Can model simple sequential flow, branching, iteration, recursion and concurrency

Sequence Diagrams 6

 Include instance names when objects are referred to

in messages or when several objects of the same

type exist in the diagram.

 The Life-Line represents the object’s life

during the interaction

 Lifelines are drawn as a box with a dashed line

descending from the center of the bottom edge

The lifeline's name is placed inside the box.

myBirthday :Date

Sequence Diagrams 7

Messages

 An interaction between two objects is performed as a message sent from one object to another (simple

operation call, Signaling, …)

 If object obj1 sends a message to another object obj2some link must exist between those two objects

Sequence Diagrams 8

Messages (Cont.)

 A message is represented by an arrow between the life lines of two objects.

 Self calls are also allowed

 The time required by the receiver object to process the

message is denoted by an activation-box.

 A message is labeled at minimum with the message name.

 Arguments and control information (conditions, iteration)

may be included.

Sequence Diagrams 9

Sequence Diagrams 10

return (optional) yes

Sequence Diagrams 11

Asynchronous Messages

 If a caller sends an asynchronous message, it can continue processing and doesn’t have to wait for a response

 We can see asynchronous calls in multithreaded

applications and in message-oriented middleware

Asynchrony gives better responsiveness and reduces the temporal coupling but is harder to debug

Sequence Diagrams 12

Object Destruction

 An object may destroy another object via a

<<destroy>> message.

 An object may destroy itself.

 Avoid modeling object destruction unless memory management is critical.

<<destroy>>

Found Message

 A found message is a message where the receiving event occurrence is known, but there is no (known) sending event occurrence

 We interpret this to be because the origin of the message

is outside the scope of the description This may for

example be noise or other activity that we do not want to describe in detail

Lost Message

 A lost message is a message where the sending event

occurrence is known, but there is no receiving event

occurrence

 We interpret this to be because the message never reached its destination

Object state and Constraint

 Sequence diagrams can show how an object changes state overtime

 We do this by placing the object state on the lifeline at the appropriate point This allows we to see very clearly

which events give rise to state changes

Object state and Constraint (cont.)

 The message acceptPayment(…) causes a state transition

on the :Order object from state unpaid to paid

 The message deliver( ) sent from the :DeliveryManager

object to the :Order object causes a state transition in

:Order from state paid to delivered.

 The timing constraint says that there must be 28 days or less between time A and time B Time A marks the point

at which the :Order object undergoes transition into the state paid, and time B marks the point at which the :Order object undergoes transition into the state delivered

Combined Fragment

 Combined fragment is an interaction fragment which

defines a combination (expression) of interaction

fragments A combined fragment is defined by an

interaction operator and corresponding interaction

operands Through the use of combined fragments the user will be able to describe a number of traces in a compact and concise manner

Combined Fragment (Cont.)

 Interaction operator could be one of:

 strict - strict sequencing

 seq - weak sequencing

 critical - critical region

 ignore - ignore

 consider - consider

 assert - assertion

 neg - negative

 The interaction operator alt means that the combined

fragment represents a choice or alternatives of behavior

At most one of the operands will be chosen The chosen operand must have an explicit or implicit guard expression that evaluates to true at this point in the interaction

 An implicit true guard is implied if the operand has no

guard

 An operand guarded by else means a guard that is the

negation of the disjunction of all other guards If none of the operands has a guard that evaluates to true, none of the operands are executed and the remainder of the enclosing interaction fragment is executed

Alternatives (Cont.)

 The interaction operator opt means that the combined

fragment represents a choice of behavior where either the (sole) operand happens or nothing happens An option is semantically equivalent to an alternative combined

fragment where there is one operand with non-empty

content and the second operand is empty

 The interaction operator loop means that the combined

fragment represents a loop The loop operand will be

repeated a number of times The loop construct represents

a recursive application of the seq operator where the loop

operand is sequenced after the result of earlier iterations

 Loop could be controlled by either or both iteration

bounds and a guard

 Loop operand could have iteration bounds which may

include a lower and an upper number of iterations of the loop Textual syntax of the loop is:

 loop-operand ::= loop [ '(' min-int [ ',' max-int ] ')' ]

 min-int ::= non-negative-integer

 max-int ::= positive-integer | '*'

Loop (Cont.)

 If loop has no bounds specified, it means potentially

infinite loop with zero as lower bound and infinite upper bound

Loop (Cont.)

 If max-int is specified, it should be greater than or equal to min-int Loop will iterate minimum the min-int number of times and at most the max-int number of times

 Besides iteration bounds loop could also have an

interaction constraint - a Boolean expression in square

brackets

 UML tries to shuffle the simplest form of for loop and

while loop : "after the minimum number of iterations

have executed and the Boolean expression is false the loop will terminate" This is clarified as "the loop will only continue if that specification evaluates to true

during execution regardless of the minimum number

of iterations specified in the loop."

Loop (Cont.)

 The interaction operator break represents a breaking or

exceptional scenario that is performed instead of the

remainder of the enclosing interaction fragment

 A break operator with a guard is chosen when the guard

is true In this case the rest of the directly enclosing

interaction fragment is ignored When the guard of the break operand is false, the break operand is ignored and the rest of the enclosing interaction fragment proceeds

Break (Cont.)

 The interaction operator par defines potentially parallel

execution of behaviors of the operands of the combined fragment Different operands can be interleaved in any way as long as the ordering imposed by each operand is preserved

 Set of traces of the parallel operator describes all the

possible ways or combinations that occurrence

specifications of the operands may be interleaved without changing the order within each operand

Parallel (Cont.)

 Search Google, Bing and Ask in any order, possibly parallel

Strict Sequencing

 The interaction operator strict requires a strict sequencing

(order) of the operands on the first level within the

combined fragment

Weak Sequencing

 The interaction operator seq means that the combined

fragment represents a weak sequencing between the

behaviors of the operands

 Weak sequencing is defined by the set of traces with these properties:

 The ordering of occurrence specifications within each of the operands is maintained.

 Occurrence specifications on different lifelines from different operands may come in any order.

 Occurrence specifications on the same lifeline from different operands are ordered such that an occurrence specification of the first operand comes before that of the second operand.

Weak Sequencing (Cont.)

Critical Region

 The interaction operator critical defines that the combined

fragment represents a critical region A critical region is a region with traces that cannot be interleaved by other

occurrence specifications (on the lifelines covered by the region) This means that the region is treated atomically

by the enclosing fragment and can't be interleaved, e.g by parallel operator

 UML defines its meaning as "there are some message

types that are not shown within this combined fragment These message types can be considered insignificant and are implicitly ignored if they appear in a corresponding execution Alternatively, one can understand ignore to

mean that the message types that are ignored can appear anywhere in the traces."

 The list of ignored messages follows the operand enclosed

in a pair of curly braces "{" and "}" Ignore operation is typically combined with other operations such as "assert ignore {m, s}."

 The interaction operator consider defines which messages

should be considered within this combined fragment,

meaning that any other message will be ignored

 The list of considered messages follows the operand

enclosed in a pair of curly braces "{" and "}" Consider

operation is typically combined with other operations such

as "assert consider {m, s}."

 The interaction operator assert means that the combined

fragment represents the assertion that the sequences of the assert operand are the only valid continuations (must be satisfied by a correct design of the system) All other

continuations result in an invalid trace

 Commit() message should occur at this point, following with evaluation of state invariant

 The interaction operator neg describes combined fragment

of traces that are defined to be negative (invalid)

 Negative traces are the traces which occur when the

system has failed

 All interaction fragments that are different from the

negative are considered positive, meaning that they

describe traces that are valid and should be possible.

 Should we receive back timeout message, it means the system has failed

 Interaction use works as:

 Copy the contents of the referred interaction to where this

interaction needs to be used,

 Substitute formal parameters with arguments,

 The interaction use is shown as a combined fragment with

operator ref

Interaction use (Cont.)

 interaction-use ::= [ attribute-name '=' ] [ collaboration-use '.' ]

interaction-name [ io-arguments ] [ ':' return-value ]

 io-arguments ::= '(' io-argument [ ',' io-argument ]* ')'

 io-argument ::= in-argument | 'out' out-argument

in the interaction that will receive interaction result Note, that this restricts results of interactions to be assigned only to

attributes.

that binds lifelines of a collaboration The interaction name is

in that case within that collaboration.

interaction

Interaction use (Cont.)

 Use Login interaction to authenticate user and assign result back to the user attribute of Site Controller

Example 1 - Facebook User Authentication in a Web Application

 Web application should be registered by Facebook to have

an application ID (client_id) and secret (client_secret)

When request to some protected Facebook resources is

received, web browser ("user agent") is redirected to

Facebook's authorization server with application ID and the URL the user should be redirected back to after the

authorization process

 User receives back Request for Permission form If the

user authorizes the application to get his/her data,

Facebook authorization server redirects back to the URI that was specified before together with authorization code ("verification string") The authorization code can be

exchanged by web application for an OAuth access token

Example 1 - Facebook User Authentication in a Web Application