UML succession Diagrams are interaction diagrams that information how work are lugged out. They record the interaction between objects in the paper definition of a collaboration. Succession Diagrams room time focus and they show the order of the communication visually by using the upright axis the the diagram to represent time what messages room sent and when.

You are watching: Sequence diagrams include symbols that represent all of the following except ____.


Sequence Diagrams captures:

the communication that takes location in a participation that one of two people realizes a use situation or an operation (instance diagrams or share diagrams)high-level interactions in between user that the system and the system, between the system and also other systems, or between subsystems (sometimes well-known as system sequence diagrams)
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Purpose of succession Diagram

Model high-level communication between active objects in a systemModel the interaction in between object instances in ~ a teamwork that realizes a usage caseModel the interaction between objects in ~ a participation that realizes one operationEither version generic interactions (showing all possible paths with the interaction) or certain instances of a interaction (showing simply one course through the interaction)

Sequence Diagrams at a Glance

Sequence Diagrams show elements as they connect over time and also they are arranged according to object (horizontally) and time (vertically):

Object DimensionThe horizontal axis shows the aspects that are affiliated in the interactionConventionally, the objects affiliated in the operation are noted from left to best according to when they take part in the blog post sequence. However, the aspects on the horizontal axis may appear in any orderTime DimensionThe vertical axis represents time proceedings (or progressing) under the page.

Note that:

Time in a sequence diagram is all a about ordering, no duration. The vertical room in an interaction diagram is not appropriate for the duration of the interaction.

Sequence diagram Example: Hotel System

Sequence diagram is an interaction diagram the details how operations are lugged out -- what messages room sent and when. Succession diagrams are arranged according to time. The time progresses together you go down the page. The objects associated in the operation are provided from left to ideal according to when they take part in the message sequence.

Below is a succession diagram because that making a hotel reservation. The object initiating the sequence of message is a preventive window.


Note That: Class and also object diagrams space static version views. Interaction diagrams space dynamic. They describe how objects collaborate.

Sequence diagram Notation

Notation DescriptionVisual Representation


a type of duty played through an reality that interacts with the topic (e.g., by exchanging signals and data)external to the subject (i.e., in the sense that an instance of an actor is no a part of the instance of its corresponding subject).represent duties played by human being users, exterior hardware, or other subjects.

Note that:

An actor does no necessarily represent a details physical entity yet merely a particular duty of part entityA human being may beat the role of several different actors and, conversely, a given actor might be play by multiple different person.


A lifeline represents an separation, personal, instance participant in the Interaction.


A thin rectangle ~ above a lifeline) represents the period during i m sorry an facet is performing an operation.The top and the bottom that the the the rectangle space aligned through the initiation and the completion time respectively

Call Message

A message specifies a details communication between Lifelines of an Interaction.Call post is a sort of article that represents an invocation of procedure of target lifeline.

Return Message

A message specifies a certain communication between Lifelines of an Interaction.Return article is a type of post that represents the happen of information ago to the caller that a synchronized former message.

Self Message

A message defines a certain communication between Lifelines of one Interaction.Self blog post is a sort of message that to represent the invocation of article of the very same lifeline.

Recursive Message

A message defines a certain communication between Lifelines of one Interaction.Recursive blog post is a sort of post that represents the invocation of post of the exact same lifeline. It"s target points to an activation on optimal of the activation wherein the post was invoked from.

Create Message

A message defines a details communication in between Lifelines of an Interaction. Produce message is a type of article that represents the instantiation that (target) lifeline.

Destroy Message

A message specifies a specific communication between Lifelines of an Interaction.Destroy article is a type of post that to represent the inquiry of damaging the lifecycle of target lifeline.

Duration Message

A message defines a specific communication in between Lifelines of one Interaction.Duration post shows the distance between two time instants because that a post invocation.


A note (comment) provides the ability to affix various remarks come elements. A comment carries no semantic force, however may contain info that is beneficial to a modeler.


Message and Focus the Control

An occasion is any suggest in an communication where something occurs.Focus the control: likewise called execution occurrence, an execution occurrenceIt shows as tall, slim rectangle on a lifeline)It to represent the period during i beg your pardon an facet is performing an operation. The top and the bottom of the rectangle room aligned v the initiation and also the perfect time respectively.

Sequence Fragments

A sequence fragment is stood for as a box, referred to as a an unified fragment, which encloses a section of the interactions in ~ a succession diagramThe fragment operator (in the top left cornet) indicates the form of fragmentFragment types: ref, assert, loop, break, alt, opt, neg
OperatorFragment Type
altAlternative lot of fragments: just the one whose problem is true will execute.
optOptional: the fragment executes only if the supplied condition is true. Identical to an alt just with one trace.
parParallel: each fragment is operation in parallel.
loopLoop: the fragment might execute multiple times, and the guard indicates the communication of iteration.
regionCritical region: the fragment deserve to have just one thread executing it in ~ once.
negNegative: the fragment reflects an invalid interaction.
refReference: describes an interaction characterized on another diagram. The frame is attracted to cover the lifelines connected in the interaction. You can specify parameters and a return value.
sdSequence diagram: offered to surround an entire sequence diagram.

Note That:

It is possible to combine frames in order to capture, e.g., loops or branches.

See more: Li, O, C Or F? Which Of The Following Has The Largest Atomic Radius ?

Combined fragment keywords: alt, opt, break, par, seq, strict, neg, critical, ignore, consider, assert and loop.Constraints space usually used to display timing constraints on messages. They can use to the timing of one article or intervals between messages.Combined Fragment Example

Sequence Diagram for Modeling Use situation Scenarios

User needs are caught as use cases that room refined into scenarios. A use case is a arsenal of interactions between external actors and a system. In UML, a use situation is:

"the specification of a sequence of actions, including variants, the a system (or entity) can perform, connecting with actors of the system."

A script is one course or circulation through a use case that explains a succession of occasions that occurs during one specific execution the a device which is often represented by a sequence diagram.


Sequence chart - Model before Code

Sequence diagrams deserve to be somewhat close come the password level, so why not simply code up that algorithm fairly than drawing it together a succession diagram?

A an excellent sequence diagram is quiet a bit over the level the the real codeSequence diagrams are language neutralNon-coders have the right to do succession diagramsEasier to do sequence diagrams as a team