Assignment 2 - Solutions

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Assignment #2 SEG3101 / Fall 2022 1/15 SEG3101 – 2022: Assignment # 2 To be done with your group (identify the members who participated). This 100-point assignment counts for 5% of your final grade. There are also 20 bonus points in this assignment. For UML, the use of modeling tools is not required here. However, tools such as PlantUML can help avoid costly syntax errors. Submit your answers (PDF) via Brightspace, no later than December 1st, 10:00pm . But do not wait and finish this assignment on a haste by leaving it until the last day! Q1. Modeling lifecycles (25 marks) You shall model the lifecycle of an application of a university graduate program at uOttawa. In this context, please assume that: 1. Once created on the Ontario Universities Admission Centre (OUAC), an application needs to be verified for completeness. 2. An incomplete application may require additional information from the student (a university transcript, the results of an English/French test, etc.). 3. For each application received (complete or not), OUAC also contacts two of the referees listed to obtain their letters of recommendation. 4. Once evaluated, a complete application (including the letters) is usually either accepted or rejected. 5. The evaluation of an application may however also be postponed if the decision would be too close to the beginning of the next semester. a) Draw a UML state machine diagram to model the lifecycle of an application that minimally covers the points above (and probably other points that make sense). Clearly document the transitions ( events [conditions] [/ actions] ). Use hierarchical states and concurrent regions if they can simplify your model. You can use Java variables and methods, but make sure they are well documented (data types and descriptions) and used consistently in your conditions and parameters. ( 20 marks ) In the following, the variables are: • allStudentInfo (Boolean): true iff all the required student info (transcript, language test, etc.) have been received. • allRecLetters (Boolean): true iff the required letters from both recommenders have been received. • tooClose (Boolean): true iff the current date is such that the decision would be too close to the beginning of the next semester. • acceptable (Boolean): true iff the student is found admissible. Functions returning such variables could also have been defined. Note the use of parallel substates here (as these things happen concurrently and are independent), and the use of short-circuiting transitions in these substates. Both parts need to be in the end pseudo-state for taking the implicit group transition to Complete.

Assignment #2 SEG3101 / Fall 2022 2/15 This diagram was “coded” with PlantUML (see code in the zip file).

Assignment #2 SEG3101 / Fall 2022 3/15 b) Describe your assumptions, in English, regarding ambiguities or incompleteness issues in the description given above. Make sure your state diagram implements your decisions. ( 5 marks ) • It is assumed here that the application must be in one of these states, for statistics purpose (and hence there is no end pseudo-state after accepted or rejected). • It is assumed that a postponed evaluation will be evaluated the next semester. • It is assumed that missing information is requested and checked until everything is there. • Some important methods for communication with recommenders and students (to ask for more info or to report on the status/verdict of the application) have been identified. • A rejected application is not reopened. A new application must hence be created and evaluated. Q2. Domain Modeling with UML Class Diagrams (25 marks) You are asked to produce a precise domain model for a finite state machine (FSM) modelling language in order to produce a modelling tool. In that FSM language, we want to represent, minimally, the following concepts (please stick to the description below; do not extrapolate based on prior knowledge of FSMs or UML). 1) Each state has a name, which is unique within the scope of a diagram. There are three special types of states (beside normal ones): start states, end states, and super states. 2) A start state has a precondition (String) whereas an end state has a postcondition (String). 3) A FSM model contains at least one FSM diagram. 4) A FSM diagram: a) Has a name and a description. b) Is composed of states and of transitions. c) Has exactly one start state, and may optionally have end states. 5) Transitions connect pairs of states that belong to the same diagram: a) A transition has a name. b) A transition has a source and a destination state. c) A transition can neither have a start state as destination nor an end state as source. d) No state can exist without at least one transition. 6) A super state references another FSM diagram a) A super state can only have one input transition and one output transition. b) The referenced FSM diagram must have at least one end state. c) A FSM diagram may be referenced by many super states. (a) Draw a UML class diagram describing your domain model. Please include appropriate classes (enumeration, abstract or concrete), their attributes (including UML types), and associations (with directions, multiplicities, compositions, and role names). No need to describe the operations or visibility (-, +, #) of attributes/roles. Be precise! ( 19 marks )

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Assignment #2 SEG3101 / Fall 2022 4/15 Note: There is always a tradeoff between what we can show with associations/multiplicities and what can be enforced via (OCL) constraints. For instance, one can create an association between FSMDiagram and StartState to indicate the start state. However, this information is not new and can be inferred from the information currently available (we call this a derived association). Note that one would still need a constraint to ensure the start state is contained in the FSM diagram! Performance issues may influence such decisions (do we need to compute the start state often? If so, such hard-coded association may be useful). Containment relationships (aggregation or composition) can add precision to some associations as well but are not really necessary in such a metamodel (unless it is used also as a file format, where each class needs to be included directly or indirectly in a top-level class, like EMF requires). (b) Several constraints will not be representable in your class diagram. Describe 2 of them precisely in terms of the concepts/attributes/roles you defined, in English (no need to use OCL unless you really, really want to). Do not create constraints for what is already covered by the class diagram, for example by multiplicities. ( 6 marks ) Constraints missing from the above diagram (again, these depend on your specific diagram): -- A FSM diagram has exactly one start state context FSMDiagram inv OneStartState: self.states -> select(s : State | s.oclIsKindOf(StartState))->size() = 1 Or, more simply… context FSMDiagram inv OneStartState2: self.states ->

Assignment #2 SEG3101 / Fall 2022 5/15 one(oclIsKindOf(StartState)) Informally: An FSM diagram has exactly one StartState among its states -- Each state name is unique within the scope of a diagram context FSMDiagram inv UniqueName: self.states -> isUnique(name) -- Each transition connects a pair of states that belong to the same diagram context Transition inv StatesAndTransitionInDiagram0: self.source.diagram = self.destination.diagram Informally: the diagram of the source of a transition is the same as the diagram of the destination of that transition The above solution is a direct translation, but it is weak as the transition could belong to a diagram different from the states it connects! The solution below ensures the transition and the states it connects belong to the same diagram. context Transition inv StatesAndTransitionInDiagram1: self.source.diagram = self.fsmDiagram and self.destination.diagram = self.fsmDiagram Informally: the diagram of the source of a transition and the diagram of the destination of that transition are both the same as the fsmDiagram of that transition. Using a different context leads to much more complex expressions… context FSMDiagram inv StatesAndTransitionInDiagram2: self.transitions -> forAll(t: Transition | ( (self.states -> includes(t.source)) and (self.states -> includes(t.destination)) ) ) -- A transition cannot have a start state as destination context Transition inv NoStartStateAsDestination: not(self.destination -> oclIsKindOf(StartState)) -- A transition cannot have an end state as source context Transition inv NoEndStateAsSource: not(self.source -> oclIsKindOf(EndState)

Assignment #2 SEG3101 / Fall 2022 6/15 -- No state can exist without at least one transition context State inv NoStateWithoutTransition: (self.toT -> notEmpty()) or (self.fromT -> notEmpty()) Informally: the toT transitons or the fromT transitions of a State is not empty. -- A super state can only have one input transition and one output transition (could be interpreted as = 1...) context SuperState inv SuperStateOneInOneOut: (self.toT -> size() <= 1) and (self.fromT -> size() <= 1) -- The FSM diagram referenced by a super state must have at least one end state context SuperState inv ReferencedDiagramWithOneEndState: self.ref.states -> exists( s : State | s->oclIsTypeOf( EndState ) ) Or, more simply… context SuperState inv ReferencedDiagramWithOneEndState2: self.ref.states -> exists( oclIsTypeOf( EndState ) ) Often, oclIsTypeOf () and oclIsKindOf () can be used interchangeably. The latter returns true if the target object is of the specified type or one of its subtype (subclasses). StartState and EndState do not have any subclass here, so these two functions become equivalent. -- A super state makes reference to *another* FSM diagram context SuperState inv SuperStateReferenceAnotherDiagram: not(self.diagram = self.ref) In all cases, it is good practice to avoid redundancy (do not repeat in constraints what is already in the class diagram, e.g., in multiplicities) and to properly name your invariants (so that one knows what is violated). Try testing your domain model (for yourselves) with likely FSM models. For example, this FSM model should be supported as an instance of your domain model: As shown in the object diagram below, this FSM model is indeed supported by our metamodel, and the constraints are all satisfied. Note that object diagrams no longer have multiplicities (the associations become binary links between two objects).

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Assignment #2 SEG3101 / Fall 2022 7/15 As shown in the object diagram below, this FSM model is indeed supported by our metamodel, and the constraints are all satisfied. Note that object diagrams no longer have multiplicities (the associations become binary links between two objects). B A E2 [x=y] E1 [true] H (Sub) FSM: Main T5 T4 T2 T1 T3 T6 T7 K E3 [x=0] FSM: Sub X1 X3 X2 Name Start [pre] Start [pre] End [post] Super (Ref) Legend S2 [x=3] S2 [x=3] S1 [y=1] S1 [y=1]

Assignment #2 SEG3101 / Fall 2022 8/15 Q3. Goal modelling (25 marks) In the following GRL model, tasks A to E can only take 0 or 100 as satisfaction values. The scale of satisfaction values for the other elements is [0...100]. a) What will be the level of satisfaction of the Manager actor for the following strategy: <A, B, C, D> (i.e., A=100, B=100, C=100, D=100, with the other tasks being at 0 by default)? ( 2 marks ) As explained in the Goal Modeling slides, the truncation in the satisfaction computation Max(0, Min (100, ...)) ensures that the satisfaction of each item is truncated to the interval [0..100] (as required in this question). Increased performance = Max(0, Min(100, ( (-25*100) + (25*100) + (0 * 60) )/100)) = 0 Simplified tasks = Max(0, Min(100, ( (-25*100) + (60*100) + (25*100) )/100)) = 60 Pattern = Max(0, Min(100, (Increased Performance*50 + Simplified Tasks*50)/(50+50))) = 30

Assignment #2 SEG3101 / Fall 2022 9/15 b) What will be the level of satisfaction of the Assistant actor for the following strategy: <B, C, D>? ( 2 marks ) Decreased Stress = Max(0, Min(100, ( (75*100) + (-50*100) + (-25 * 0)/100)) = 25 Assistant = Max(0, Min(100, (Stress decreased*100)/100)) = 25 c) How many valid GRL strategies (where a valid strategy is a combination of tasks A to E, as in the previous question, that satisfies the decomposition constraints) will allow the System actor to achieve a satisfaction level of 100? ( 4 marks ) For System to be 100, both Function 1 and Function 2 must be 100. For Function 1 to be 100, since we have an inclusive OR, we must select A, B or <A,B>. For Function 2 to be 100, since we have an AND/AND decomposition, Subgoal 1 and Subgoal 2 must both be 100. Subgoal 2 has an XOR decomposition, so D or E must be selected, but not both. Subgoal 1 has an inclusive OR decomposition, so C or D or <C,D> must be selected. This means that Function 2 is satisfied with <C,D>, <C,E> and D alone. By composing these two sets of three selections, we get 9 strategies: 1: <A,D> 2: <A,C,E> 3: <A,C,D> 4: <A,B,C,D> 5: <A,B,C,E> 6: <A,B,D> 7: <B,C,D> 8: <B,C,E> 9: <B,D>

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Assignment #2 SEG3101 / Fall 2022 10/15 Here are the ratings for each of these strategies for all items: d) What are the valid strategies (as there could be more than one) that will maximize the level of satisfaction of the Manager actor while ensuring that the System actor has a 100 satisfaction level? Please list these strategies (see format in the previous sub-questions) and indicate this maximum satisfaction value for the Manager actor. ( 4 marks ) Strategy 8 <B,C,E> maximizes Patron, with a satisfaction of 60. See the table. e) Similarly, what are the valid strategies that will maximize the level of satisfaction of the Assistant actor while ensuring that the System actor has a 100 satisfaction level? Please list these strategies and indicate this maximum satisfaction value for the Assistant actor. ( 4 marks ) Strategies 6 <A,B,D> and 9 <B,D> maximize Assistant, with a satisfaction of 75. f) Finally, what are the valid strategies that will maximize the level of satisfaction of the entire model (using the relative importance weights of the actors) while ensuring that the System actor has a 100 satisfaction level? Please list these strategies. ( 4 marks ) Strategy 9 <B,D> maximizes the whole model, with a satisfaction of 12.5*60/100 + 75*40/100 = 37.5

Assignment #2 SEG3101 / Fall 2022 11/15 Q4. Process modelling (25 marks) a) Observe the following BPMN process models (Test1 and Test2). Which ones support each of the following four execution traces? Your answers may be: None , Test1 , Test2 , or Both ( 4 x 2 marks ) • Trace1 = < Fill form, Send form, Check total, Check name, Reject, Inform > Both • Trace2 = < Fill form, Send form, Check name, Reject, Inform > None of them. In both cases, Check total is also required (just before or just after Check name) because Check name and Check total are in parallel (gateway +). In BPMN, gateway X is a choice. • Trace3 = < Fill form, Send form, Check name, Check total, Resubmit, Send form, Check total, Check name, Reject, Inform > Test 1. Test2 does not support the loop with Resubmit • Trace4 = < Fill form, Send form, Check name, Check total, Accept, Reject, Inform > None. In both cases, Accept is mutually exclusive with Reject in the choice b) What is the number of complete execution traces possible for the Test2 model? ( 3 marks ) 4, and these are: < Fill form, Send form, Check total, Check name, Accept, Inform > < Fill form, Send form, Check name, Check total, Accept, Inform > < Fill form, Send form, Check total, Check name, Reject, Inform >

Assignment #2 SEG3101 / Fall 2022 12/15 < Fill form, Send form, Check name, Check total, Reject, Inform > c) What is the number of complete execution traces possible for the Test1 model, if we limit the number of allowed iterations to a maximum of 3? ( 4 marks ) 2x2 (pas d’itération) + 2x2x2 (une itération) + 2x2x2x2 (deux itérations) + 2x2x2x2x2 (trois itérations) = 60 d) What are the two major problems in the following UCM process model? (An informal description of the process is not provided here as the problems are not at that level) ( 2 x 3 marks ) 1) The first OR-fork has incomplete conditions (what to do when cost = 100?): dead end. 2) The path [cost<100], [!enoughTime], [cost>120] is infeasible. Postponed is not reachable. These are similar problems to those we can often see in programming. e) What is the major problem in the following UCM process model? (An informal description of the process is not provided here as the problem is not at that level) ( 4 marks ) The [!OK] path will be blocked at the AND junction, because it needs to go through Retry to synchronize, but Retry cannot be executed without prior synchronization. This is a typical concurrency problem in process models.

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Assignment #2 SEG3101 / Fall 2022 13/15 Q5. SPL and Feature Models (25 marks) Use the following feature model diagram with three constraints. Remember that the OR decomposition used here is an inclusive OR where at least one child feature is required. a) Are these configurations valid and, if not , why ? ( 5 x 2 marks ) • Config1 = {ATM, Money slot, Card reader, Shielding window, Wall installation} No. Protection is missing • Config2 = {ATM, Money slot, Card reader, Protection, Shielding window, Wall installation, Authentication, PIN check, Biometric check, Iris, Fingerprint, Voice} No. Fingerprint must be excluded (C1). • Config3 = {ATM, Money slot, Card reader, Protection, Shielding window, Wall installation, Authentication, PIN check, Biometric check, Voice, Printer, Laser} Yes • Config4 = {ATM, Money slot, Card reader, Protection, Shielding window, Wall installation, Authentication, PIN check, Biometric check, Iris, Printer, Ink} No, Ink must be excluded (C2) • Config5 = {ATM, Money slot, Card reader, Protection, Shielding window, Printer, Ink} No, Wall installation must be included b) A dead feature is a feature that is not part of any valid configuration. Are there any dead features in this model and, if so, what are they? ( 3 marks ) Fingerprint (via C1), Ink (via C2), in red in the model (which could be simplified). c) A core feature is defined as a feature that belongs to all valid configurations. In addition to the root feature (ATM), what are the other core features of this model? ( 3 marks ) Money slot, Card reader, Shielding window (via C3), Protection (via Shielding Window), Wall installation (via Protection), those are marked green in the model d) What is the number of valid configurations for this model? Briefly explain why. ( 4 marks ) - Authentication is optional but must have Biometric check, which has 3 itself options (Iris, Voice, Iris+Voice) if selected. Fingerprint is a dead feature. So there are 4 options for this branch: unselected, or one of the 3 Biometric check options. - Printer is optional, but if this option is selected, then Laser must be selected (Ink is a dead feature. So there are 2 options here: unselected, or Printer+Laser.

Assignment #2 SEG3101 / Fall 2022 14/15 - So there are 4*2 = 8 valid configurations: o C1={ATM, Money slot, Card reader, Protection, Shielding window, Wall installation} o C2={ATM, Money slot, Card reader, Protection, Shielding window, Wall installation, Authentication, PIN check, Biometric check, Iris} o C3={ATM, Money slot, Card reader, Protection, Shielding window, Wall installation, Authentication, PIN check, Biometric check, Voice} o C4={ATM, Money slot, Card reader, Protection, Shielding window, Wall installation, Authentication, PIN check, Biometric check, Iris, Voice} o C5={ATM, Money slot, Card reader, Protection, Shielding window, Wall installation, Printer, Laser} o C6={ATM, Money slot, Card reader, Protection, Shielding window, Wall installation, Authentication, PIN check, Biometric check, Iris, Printer, Laser } o C7={ATM, Money slot, Card reader, Protection, Shielding window, Wall installation, Authentication, PIN check, Biometric check, Voice, Printer, Laser } o C8={ATM, Money slot, Card reader, Protection, Shielding window, Wall installation, Authentication, PIN check, Biometric check, Iris, Voice, Printer, Laser } e) If we combine the original feature model with the following goal model (which handles some non-functional requirements), what are the valid configurations that will maximize the satisfaction of the Bank? ( 5 marks ) - Don't forget that Fingerprint and Ink are dead features (cannot be selected) and that Shielding window and Wall installation - C4={ATM, Money slot, Card reader, Protection, Shielding window, Wall installation, Authentication, PIN check, Biometric check, Iris, Voice}is the best configuration, with a satisfaction of 70 per Bank - C1 → 35, C2 → 60, C3 → 63, C4 → 70, C5 → 35, C6 → 52, C7 → 63, C8 → 63

Assignment #2 SEG3101 / Fall 2022 15/15 Description of group and roles Provide a list of group members and their contributions for this deliverable. If for some legitimate reasons the work distribution is unbalanced, please state these reasons in a short paragraph. Note that the information provided here might be used to adjust the assignment grade for the group members. Start early and do not let your group partners down at the last minute!

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