1 Specification of IT Systems Mandatory Exercise Week 1

2 Assignment 1.Give three example on reactive systems, which you are familiar with. For each system give a brief informal description. 1.Subject domain of the system 2.Any relevant connection domains between the subject domain and the system. 3.Cause and effect chain concerning the system 4.Examples of requirements and constraints for the system. 2.Choose one of the systems from (1), which you will use throughout the course. Discuss why it is the right system.

3 Exercise 1 - Example 1  Servicemen Workflow System  This is a system that handles work items for servicemen (Servicemen Workflow System (SWS)). A work item is a piece of work with attributes such as location, deadline, restrictions, materials, and a short description of a problem. The servicemen work at different sites. Servicemen meet in the morning and pick up tasks that go well together. By this is meant that the type of work items are homogenous in some respect, e.g. at the same location, same type of job, or whatever strategy the serviceman choose them by. Servicemen when working the servicemen receive new work items if they apply to them. This is the case if the servicemen is at a site where that the new work item is located. The servicemen are connected to the system through high-end mobile phones.

4 Exercise 1 - Example 1 - Subject domain Physical Entity:  Servicemen  Room  Building  AV  Computer Conceptual Entity:  Work item allocation Lexical Entity:  Work item  Process definition  Process instance

5 Exercise 1 - Example 1 - Connection domain  Mobile phone  Location system  Laptop

6 Exercise 1 - Example 1 - Cause and effect chain (1) Event: Serviceman request to see available work items by using his mobile phone. Events that may happen anyway: Serviceman calls a friend, serviceman checks the time on his mobile phone, … Stimulus: The system detects the request from the mobile phone, and the location of the mobile phone Response: A list of available work items, sorted by, among other criteria, the location of the mobile phone. Action: The serviceman can see the work items on the display of his phone.

7 Exercise 1 - Example 1 - Cause and effect chain (2) Condition: The serviceman’s phone is located at the work item’s location. Event: A new work item is added by a user of the system. Events that may happen anyway: A serviceman walks onto another site, … Stimulus: The system detects the work item. Response: The work item is broadcasted to anyone at that location. Action: Any serviceman at the work items location will be made aware of the new work item, e.g., by a special sound on their mobile phone.

8 Exercise 1 - Example 1 - Cause and effect chain (3) Condition: A job cannot be completed because of lack of parts. Event: A serviceman returns the work item, by stating that it has not been completed and need some specific parts. Stimulus: The system detects the request. Response: The system generates an order for the requested parts, either as an external order to a company, or as a work item, if the needed parts are available at some location. The new work item would then be something like “Move these parts to this room”. The same work item that was returned, is then reassigned to a serviceman, when the parts have arrived. Action: The serviceman is notified that the work item return succeeded.

9 Exercise 1 - Example 1 - Requirements  The system must utilize the location of the servicemen mobile phones, when distributing work items.  The system must give accurate deadlines for when work items/process instances are completed.  It must be possible to share process definitions with others.  It must be possible to track a process instance  …

10 Exercise 1 - Example 1 - Constraints  The system can only locate mobile phones, not the servicemen.  The system cannot locate parts needed for a work item. Information regarding parts a is inputted by a worker and must be considered valid. z…

11 Exercise 1 - Example 2 and 3 zSame procedure as for example 1. Examples of other systems: yCruise controller ySupermarket inventory system y…

12 Exercise 2 (1) We choose the SWS from Section. The system displays the following characteristics of a reactive system (cf. [Wieringa, Fig. 1.1]): Highly interactive: Yes, it is possible to input and receive work items to the SWS at all time. Nonterminating process: Yes, SWS is running all the time. Interrupt-driven: Yes, work items that are scheduled can be withdrawn from a serviceman’s work queue. State-dependent: response Yes, e.g. the response a serviceman get from SWS is depending on what work items exists in the system.

13 Exercise 2 (2) Environment-oriented: response Yes, e.g. submitting a work item that could be completed due to lack of parts, will first make the SWS interact with other systems to either order or find those parts and then schedule new work items accordingly. Parallel processes: Yes, work items that do not depend on each other, can be executed in parallel. Stringent real-time requirements: No, e.g. the SWS is not expected to re- spond to request within seconds.