Start, Stop and Handle Equipment Faults on Overlaid Routes and route Groups. The reclaimer buckets would carry a large car. Despite the obvious value of a guidebook's roadmaps and narratives, we information technologists too often embark on software development projects without them. Hence, the starting of conveyors is actually staggered in order to spread the load on the power station. Transport Product will be a big use case, but this captures the essence, the reason for the existence of our system, the value that it provides for our actor and our stakeholders. I can't emphasize this enough, which is why I'm repeating it here. In this context, a "system" is something being developed or operated, such as a web site. At the top of Figure 8 I have extracted a couple of abstract use cases: one for starting a route and another for stopping a route. "Starting/Positioning Stragegy 2.1" describes a staggered start, which requires that all the equipment be in position before you start the route. Finally, I'll discuss some lessons learned and present some recommendations. The System advises the CRO that the Route must be positioned prior to starting. Rui Azevedo. The client is one of the world's largest iron ore producers with an iron ore export facility in the Northwest of Western Australia at Port Headland. The system architecture needs to resolve issues such as ensuring desired behavior when signals are received very close together, in various orders or very frequently. The first of these is that traditional approaches to writing requirements may initially appear to be more rigorous and precise, particularly with the variety of use case guidance presented in current books and papers. © Cinergix Pty Ltd (Australia) 2020 | All Rights Reserved, View and share this diagram and more in your device, edit this template and create your own diagram. With a real-time system, there might not be a lot of user interaction at all. You can quickly see that PT use cases fall into 4 groups: Operation, Administration, Configuration and System Startup. It is also used to draw diagrams of various types such as Entity Relationship diagrams, UML diagrams, Flowcharts, Network diagrams, etc. Firstly it makes testing difficult because the behavior described is not externally visible. Another example of an alternate flow would be a description of what happens when an operator cancels a previously requested action. As I mentioned earlier, use cases describe "flows of events". Indeed, use case diagram shows what we want the system to do rather than describe how it can be accomplished. Use case diagrams are a way to capture the system's functionality and requirements in UML diagrams. One of the things we have to be careful to avoid is loading the wrong product into a ship. Use Cases: the Pros and Cons ... As object technology is applied to ever increasingly complex projects, the simple ... not easily handle the existence of branches and loops in the logic of a use case. In the use-case specifications we used footnotes to indicate alternate flows with the footnote text containing a navigable cross-reference to the relevant document section. *, The System determines that the conditions listed in Special Requirements, Section 3.1, "Conditions that prevent starting," do not apply to the Route. Iteration 2 test cases for the Start Route use case are shown in Figure 10. Hi guys!! This article derives from the following session of the 2003 Rational User Conference in Orlando, Florida. It's very important to focus on identifying the actors at the start of this whole process because that bounds your system, clearly indicating what is in-scope and what is out-of-scope. In order to meet the productivity requirements, the control system adopts aggressive starting and fault-handling strategies. Imagine flying to an unfamiliar foreign country where you plan to rent a car and tour the sights. Each of these processes is quite complex in itself, and if we put that detail in the basic flow, it would make the basic flow long and difficult to understand. Supports over 40+ diagram types and has 1000’s of professionally drawn templates. including Use Case diagram.. How to create use case diagram in Dia: For each diagram type, it has a specific section like UML, Assorted, Flowchart, etc. The CRO is the Control Room Operator. (See lesson 9). The conveyors are capable of moving 10,000 tons of ore an hour in this system! It is important to provide a detailed description if possible including a nominal scenario (typical sequence) and alternate sequences on the particular cases. As a result, development teams often wander far from the project objectives - at considerable expense and delay. 1. De granulariteit van een use case is gelijk aan die van … In the Figure 4, the arrow from the CRO to the Transport Product use case, indicates that this operator initiates or starts this use case. If I were to hide all those abstract use cases, you could still see what the primary function of this system is quite clearly. This work is based on both the IBM(r) Rational Unified Process(r) (RUP(r)), and the work that's described in the book, "Use Case Modeling", by Kurt Bittner and Ian Spence. You need to fully describe what is important to the customer while providing sufficient detail for development, test and documentation. Suffice to say, the criteria was based on a risk assessment in accordance with RUP. Real-time systems can be highly algorithmic, and use cases may not be the best way of documenting algorithms. There are common ways to do it, but as long as your use case diagram is easy to understand, it doesn’t matter if you deviate from the norms. It captures the dynamic behavior of a live system. The one on the left is the PMAC, which is an existing system which hosts our user interface. Such an example may be useful to illustrate a point, but is often not particularly helpful when dealing with a large and complex system. Bronnen, noten en/of referenties Deze pagina is voor het laatst bewerkt op 18 feb 2020 om 16:55. Do not introduce design. On the left, we have a use case with a basic flow, alternate flows and subflows. The other one of interest on bottom left is the RSMT (the Root System Maintenance Technician). Unless the process is related to the purpose of this system, such as a "Monitor Building" use case in a building monitoring system, what you should be doing here is writing requirements in the supplementary specification. If you write a requirement describing something that is not visible, you can't test it. Figure 3 shows the top-level use-case diagram for the PT System. An important structure here is the Subflow. These requirements might drive you to design processes that poll equipment or the equipment might generate interrupts, but these are design considerations and don't belong in the requirements domain. Do you want that? Depending on your requirement you can use that data in different ways. A use case diagram consists of the system, the related use cases and … In use case diagrams there are external actors (which may be users or processes that interact with your system). 2. The Principles of our Approach ... Use Case – a single Scenario – any number of Alternative Flows may be invoked. Adjustment of Feed and Speed on Conveyor Fault. The port facility at Port Headland has its own power station! Secondly, if you put design information in the use case, you are required to comply with that because it's a specification, so not only do you have to demonstrate compliance with it, it also constrains your designers. Note: listed items in bold denote a glossary item, whereas list elements ending in an * symbol denote an Alternate Flow Indicator. The rules of writing traditional declarative requirements still apply. Everything about this system is big. 1. Below is a sample use case diagram which I have prepared for reference purpose for a sample project (much like Facebook). On this project, I used to tell the use case modelers regularly to imagine they were the customer flying over the port facility and ask themselves, what they wanted to see happening. Those with a development background tend to take an internal rather than an external point-of-view. The important point about structuring is that you must avoid making the use case model, and the use cases, difficult to understand. The most important one is at the top left. Don't write use cases for internal system monitoring processes. Freezing the use cases too early in a project causes a lot of problems because, as you and your customer understand the requirements better, you will find opportunities for restructuring the use cases or you will need to introduce new use cases or you will make changes to existing use cases. Vergelijk een use case met een procestaak. 2. The operator or stakeholder derives no value from simply selecting, starting or stopping a route. This describes what happens when everything goes right. In each use case, you simply describe what you want the system to do under a given set of circumstances. In this Use Case case study, I am going to present a case study of airport check-in system. You could completely document the requirements for a system without using these techniques. A digression to describe the handling of an equipment fault is a good example of an alternate flow. The example that's often used in the literature is the ubiquitous Automatic Teller Machine. In the PT System, the Reclaimer is a system that we interact with. 8. If it were just a user interface as far as our system is concerned, we wouldn't need to document it as an actor because the actor is actually the CRO. So what is a use case diagram? Wherever possible, equipment is left running until there is a possibility of ore spilling. Use Case Diagram. There are a lot of requirements, particularly with a real-time system, that do not belong in the use case flows of events. a use case instance • use case - a collection of related success and failure scenarios, describing actors using the system to Whenever you want to start a conveyor, the PT System has to ask permission from the power station. All the same rules that apply to documenting IT systems using use cases apply here. (Use case then written in terms of internal signals). Don't be afraid to capture the detail. It could be transporting tablets in a pharmaceutical factory, for example. On the left is a package of Operators. We can't modify that. You can see the reclaimers which pick up the ore from the stockpiles and take it to the ships. Structuring of the use cases allows you to avoid duplication and to ensure that there is only a single point of maintenance of use case text. At some point, you have to stop tinkering with the use-case model and actually develop the system! Use cases put the requirements in the context of the value the system provides to the user and/or stakeholders. The use-case specifications are long and very detailed. Use cases are a set of actions, services, and functions that the system needs to perform. The PT System shall, upon notification of fault requiring upstream interlocks to be set to "False", set Upstream interlocks to False within 0.60 second. Use Activity Diagrams to make complex use cases easier to understand. Don't "freeze" the use cases too soon. Use cases are supposed to be easily read by everybody, but that doesn't mean you can take somebody off the street and give them a complex use case describing a complex system and have them understand it. In the early stages of a development project, use case diagrams (use case: In a use case diagram, a representation of a set of events that occurs when an actor uses a system to complete a process. Some of the conveyors are 7 kilometers long and can take up to 15 minutes to start. Purpose: Use case diagram example shows some simplified view of software licensing use cases supported by Sentinel EMS Application. Use cases don't interact directly. It would help us to understand the role of various actors in our project. In our example, we have the controller room operator who is the actor, but the company is actually getting the value by virtue of the system moving product from one place to another. The car-dumping facilities are in the near-vertical line in the middle. The System determines that the entire Route is. 2. Usually, they are nonfunctional requirements that relate to performance, availability, and so on. When you are working with a real-time system, you will probably find that you have a lot more requirements in the supplementary specification than you would if you were developing an IT system. We could show each equipment actor but the diagram would become very cluttered. Does anyone know where I can find an example of a use case diagram with <> and <> relationships between use cases, inheritance relationships between actors and use cases, and respective textual descriptions? This facilitates ensuring that all requirements are tested and allows the test cases impacted by requirements changes to be identified. Typically, a use case will refer to an algorithm that is documented elsewhere, leaving the use case specification rather empty. Requirements changes will occur, but they need to be managed within the constraints of an iterative process with proper impact assessment and associated schedule and budget changes if appropriate. You are not documenting how the system does what it is required to do. Structuring techniques are shown in Figure 7. 3. Your developers may have extensive domain experience and you're happy with that. Use cases that relate to operation of the PT System are shown in Figure 4. Real-time systems can have minimal interactions with the user, and, again, this is a consideration where specifying such a system with use cases is concerned. The System checks whether the entire Route is purged (no material on the conveyors). The CRO directs the System to start a previously, The System determines that the Route will be a, The System determines that the Route Start Command is valid. This is despite the many books, papers and training courses available on the subject. Steps "a", "b" and "c" of step 16 also refer to subflows. Create a use case diagram with draw.io. You can see the stockpiles in the North and South yards, conveyors running between the car-dumpers and crusher, and crusher and stockpiles. In this particular case, if we have material on the wharf conveyor and it has been stopped because the conveyor might end up dumping ore on the deck of the ship, we have to raise an alarm and advise the operator. Focus on externally visible behavior. Those that relate specifically to a particular use case are captured in the Special Requirements section of the associated use-case specification. Use Creately’s easy online diagram editor to edit this diagram, collaborate with others and export results to multiple image formats. Activity Diagrams can be created as the use case specifications are written. We don't want to be developing things we're not being paid for! Here is the allocation: Use case analysis is the process of identifying objects, classes, class attributes and class operations. Whereas the existing system starts one conveyor in a route at a time, and when it is up to speed, starts the next one and so on, the new control system can start all the conveyors in a route simultaneously - keep in mind that we have conveyors with different lengths, and therefore start times, and capacities. You will never be able to get a perfect use-case model. The PT System Maintenance Procedures shall comply with the Client's maintenance strategy for real-time PLC control systems. 5. Starting with the basics you can however master Use Cases in 30 minutes. There are a number of reasons why you shouldn't do this. 1. For real-time systems, expect a greater percentage of the system requirements to reside in the supplementary specification. If during a ship hatch change, burden is on the wharf conveyor at or within the gross stopping distance of the shiploader, the System shall: Issue a request to the SHLS to stop the shiploader boom conveyor, Give context to the requirements, clearly showing why a system is needed, Make requirements much easier to read and understand than traditional declarative requirements by placing the requirements in chronological sequences, Make it easier to gain agreement with customers because they can read and understand them more easily, Are useful as a basis for project planning, analysis, design, test and documentation. IBM and Red Hat — the next chapter of open innovation. The subflow becomes a new use case that is included by the original use case. Firstly, let's revisit the definition of a use case: A Use Case defines a sequence of actions performed by a system, that yields an observable result of value to an Actor or Stakeholder. Actors: Stick figures that represent the people actually employing the use cases. It is possible to develop a system that meets the customer's requirements even though the use-case model might not be perfect.