Objectoriented modeling Sequence diagrams Karolina Muszyska Based on

Object-oriented modeling Sequence diagrams Karolina Muszyńska Based on: S. Wrycza, B. Marcinkowski, K. Wyrzykowski „Język UML 2. 0 w modelowaniu SI”

Object Modeling �Dynamic view – sequence diagrams ◦ ◦ role and types of sequence diagrams basic concepts advanced concepts examples 2

Sequence Diagram –role �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

Sequence Diagrams –types 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

Sequence Diagrams –basic concepts �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

Sequence Diagrams –basic concepts Classifier (actor, object, interface, package) Lifeline Message 6

Sequence Diagrams –basic concepts Activation Deactivation Execution specification 7

Sequence Diagrams – advanced concepts �Types of messages �Creating and destroying objects �Guard conditions �Combined fragments with interaction operators �Interaction occurrences 8

Sequence Diagrams – advanced concepts 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

Sequence Diagrams – advanced concepts Synchronous message Asynchronous message 10

Sequence Diagrams – advanced concepts Return message Self message 11

Sequence Diagrams – advanced concepts 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

Sequence Diagrams – advanced concepts 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

Sequence Diagrams – advanced concepts <<Create>> message <<Destroy>> message 14

Sequence Diagrams – advanced concepts � 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

Sequence Diagrams – advanced concepts Guarding condition 16

Sequence Diagrams – advanced concepts � 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: 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

Sequence Diagrams – advanced concepts 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 when the combined fragment is executed other interactions are ignored � iteration (loop) – means repeating the operand a specified number of times 18

Sequence Diagrams – advanced concepts 19

Sequence Diagrams – advanced concepts 20

Sequence Diagrams – advanced concepts 21

Sequence Diagrams – advanced concepts 22

Sequence Diagrams – advanced concepts � 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 23

Sequence Diagrams – advanced concepts Interaction occurrence 24

Building a sequence diagram � 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 25

Additional information and examples � UML Sequence Diagrams: Guidelines https: //msdn. microsoft. com/enus/library/dd 409389. aspx � UML Sequence Diagrams: Reference � https: //msdn. microsoft. com/enus/library/dd 409377. aspx � Sequence Diagrams http: //www. uml-diagrams. org/sequencediagrams. html � UML Sequence Diagrams Examples http: //www. uml-diagrams. org/sequencediagrams-examples. html 26