Karolina Muszyńska Based on: S. Wrycza, B. Marcinkowski, K. Wyrzykowski „Język UML 2.0 w modelowaniu SI”

 Dynamic view – sequence diagrams ◦ role and types of sequence diagrams ◦ basic concepts ◦ advanced concepts ◦ examples 2

 Sequence diagram is a kind of interaction diagram, describing interactions among system classifiers in the form of sequence of messages interchanged between them during a certain period of time.  Sequence diagrams are closely related to use case scenarios as they document their functionality.  Interaction is shown on the sequence diagram in two dimensions: o Horizontal - static dimension where the system classifiers taking part in the interaction are placed o Vertical – dynamic dimension, with the time line showing chronically arranged messages 3

Depending on the degree of abstraction three types of sequence diagrams can be specified:  Conceptual sequence diagram – using only basic concepts, for quick and general overview of the system interactions  Generic sequence diagram – is the basis for software specification and uses all available concepts; this type of diagram includes the main and all alternative scenarios of a use case and it can be used for automatic generation of program code  Instance sequence diagram – a diagram describing one particular scenario of a use case; there may be several instance diagrams for one generic diagram 4

 Classifier – abstract category of system modeling in UML (e.g. actor, object, interface, component, package, etc.)  Message – describes a control flow in the system; it determines the sequence and place of execution of operations; messages are arranged according to the sequence of their appearance – the later they occur the lower they appear on the diagram  Each classifier has a lifeline that represents its life time; the “X” mark at the end of the lifeline indicates the point at which the object ceases to exist in the system  The execution specification shows time period during which the classifier performs an operation (processing, calculating, communicating with other classifiers or executing complex algorithms); the execution specification is initiated with an activation and ended with deactivation. 5

6 Classifier (actor, object, interface, package) Message Lifeline

7 Activation Execution specification Deactivation

 Types of messages  Creating and destroying objects  Guard conditions  Combined fragments with interaction operators  Interaction occurrences 8

Message types:  synchronous message – passes control from the sender classifier to the receiver classifier  asynchronous message – does not pass control, does not wait for an answer from the receiver, may continue processing  return message – indicates control return to the sender classifier after synchronous message and may also initiate a certain operation  self message – message sent by the classifier to itself resulting in calling its own operation; self message is a certain kind of iteration, which creates a nested execution specification 9

10 Asynchronous message Synchronous message

11 Self message Return message

Other message types:  lost message – message sent from a known sender to an unknown receiver (temporary message)  found message – message whose sender is unknown (may be an external signal, stimulus)  balking message – message which will not be handled by the receiver classifier if it cannot be handled immediately  timeout message – similar to balking message although sender classifier is willing to wait for handling the operation for a specified period of time 12

Creating and destroying objects:  „create” stereotype message – results in creation of an object, which is situated below the primary existing classifiers, corresponding with the time of its creation  „destroy” stereotype message – results in destruction of an object 13

14 > message

 Guard condition – a criterion connected with the message, on fulfillment of which depends the execution of a specified operation.  If a condition referring to a certain message is not met the operation indicated by the message is not executed.  Conditions are placed in square brackets before the message name  Realization of a message can be conditioned by more than one condition 15

16 Guarding condition

alt – alternative opt – option break – interruption loop – iteration neg – improper functionality par - concurrency critical – critical region assert – formula consider – significance ignore – insignificance stricte – strict order seq – weak order 17  Combined fragment – is a logically consistent area of interaction, a part of a sequence diagram characterized by specific properties defined by the interaction operator  Interaction operator – specifies the functionality realized by the combined fragment  Interaction operators:

18 Selected, most common operators:  alternative (alt) – means a possibility to choose only one of all presented interaction operands within the combined fragment, depending on the condition assigned to the operand  option (opt ) – means that the operand within the combined fragment will occur or will be omitted, depending on the condition  interruption (break) – is a abbreviated form of alt with only one defined operand and when the combined fragment is executed other interactions are ignored  iteration (loop) – means repeating the operand a specified number of times

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23  Interaction occurrence – is a reference to a linked interaction diagram, placed within the base diagram  Interaction occurrences are especially useful in case of extensive sequence diagrams, which refer to other diagrams defined earlier  Interaction occurrence can be invoked either by a message or by time factor

24 Interaction occurrence

25  Analysis of a selected use case and its scenarios  Identification of classifiers taking part in the interaction  Development of conceptual sequence diagram including (identified classifiers, messages and execution specifications)  Development of a generic sequence diagram on the basis of the conceptual diagram by adding advanced concepts like: different message types, conditions, combined fragments, interaction occurrences  Optional development of instance sequence diagrams for a selected generic diagram

26  UML Sequence Diagrams: Guidelines us/library/dd aspx us/library/dd aspx  UML Sequence Diagrams: Reference  us/library/dd aspx us/library/dd aspx  Sequence Diagrams diagrams.html diagrams.html  UML Sequence Diagrams Examples diagrams-examples.html diagrams-examples.html