![]() ![]() I may have chosen to apply the notation in “non-standard” ways.Although these diagrams were thoroughly reviewed for the book, and have been reviewed by thousands of people online since then, an error may have gotten past of us. I may have gotten it wrong in the first place.The UML evolves over time, and I may not have kept the diagrams up to date. The notation may have evolved from when I originally developed the diagrams.The notation used in these diagrams, particularly the hand drawn ones, may not conform perfectly to the current version of the UML for one or more of reasons: This artifact description is excerpted from Chapter 11 of The Object Primer 3rd Edition: Agile Model Driven Development with UML 2. For the few times that you need to explore timing issues free form diagrams will very likely suffice. In my opinion very few developers will find that they need UML timing diagrams, so I really can’t recommend that you invest the time to learn them. I draw timing diagrams on whiteboards, I don’t know of any mainstream modeling tool oriented towards business application development that supports this kind of diagram. The more lifelines you try to model at once the harder it is to draw the diagram so two lifelines is about as complex as I like to get. ![]() Timing diagram (robust notation).īoth notations have their purposes, although the robust notation seems the more useful of the two particularly for objects that move back and forth between states. Unique to timing diagrams are timing rulers, depicted as tick mark values along the bottom of the diagram.įigure 2. Timing constraints and time observations can be applied to a variety of UML diagrams, including all forms of interaction diagrams such as sequence diagrams and communication diagrams, although I find them most useful on timing diagrams. A timing constraint, is shown as are time observations ( t=Nov 25 and t=Dec 1). Several ways to indicate time are shown in Figure 2. The arrows between timelines are messages between the objects. Events/stimuli, such as Holiday Break and Break Ends, are optionally labeled at transition points to indicate the reason for the change. The states/conditions applicable to the lifeline, such as Mark Student Work and Idle, are listed along the left-hand side of the diagram. The box lines are called state timelines, in this case there are discrete transitions between states resulting in a box line although had the transitions been continuous in nature (such as the change in temperature) a curvy line would have been drawn. A UML frame is being used to bound the two lifelines (that of the professor and the teaching assistant) we could very easily have modeled more lifelines simply by adding other sections to the frame. In this jaded example the professor delivers the seminar and marks student work and the teaching assistant develops the course material just in time for it to be taught. Remember AM’s Apply the Right Artifact(s) practice and use the right model for the job.įigure 2 depicts a timing diagram which explores the details of what happens while a seminar is being taught. That’s perfectly fine because I’m using each diagram for its individual strengths – concise timing diagrams are good at exploring one or more objects throughout a period of time and state machine diagrams are good at exploring the detailed transitions between states as the result of events (either external or internal). Several states from the state machine diagram are encompassed by the Enrolling Students state of the timing diagram. It’s interesting to note the differences between the timing diagram of Figure 1 and the state machine diagram. Along the bottom of the diagram timing constraints are shown, in this case indicating the period of time during which the seminar is in each state.įigure 1. When the two lines cross one another it indicates a transition point between states. In this case I’m using them to show the value of the state of a seminar, but you could also explore the value of a single attribute of an object if you so choose. ![]() The two lines surrounding the states are called a general value lifeline. The critical states that the seminar exhibits – Proposed, Scheduled, Enrolling Students, Being Taught, Final Exams, Closed – are listed across the diagram. The :Seminar label indicates that the lifeline being explored is that of an instance of Seminar. Figure 1 depicts the lifecycle of a single seminar, showing its timeline quite clearly. Timing diagrams are often used to design embedded software, such as control software for fuel injection system in an automobile, although they occasionally have their uses for business software too. There are two basic flavors of timing diagram, the concise notation depicted in Figure 1 and the robust notation depicted in Figure 2. They are used to explore the behaviors of one or more objects throughout a given period of time. Timing diagrams are one of the new artifacts added to UML 2. ![]()
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