Class Exercise I: Use Cases

1. Class Exercise I: Use Cases Deborah McGuinness and Joanne Luciano with Peter Fox and Li Ding CSCI-6962-01 Week 4, September 27, 2010 Presented by Peter Fox

2. Contents • Use case introduction • Elements of use case documentation • Class exercise – use cases in real-time • Assignment reading: Ontology Tool Summary, Pellet, OWL-S, SAWSDL, Wine Agent

3. Semantic Web Methodology and Technology Development Process • Establish and improve a well-defined methodology vision for Semantic Technology based application development • Leverage controlled vocabularies, et c. Adopt Technology Approach Leverage Technology Infrastructure Science/Expert Review & Iteration Rapid Prototype Open World: Evolve, Iterate, Redesign, Redeploy Use Tools Analysis Use Case Develop model/ ontology Small Team, mixed skills

4. Developed for NASA TIWG Use Case • A use case is a collection of possible sequences of interactions between the system under discussion and its Users (or Actors), relating to a particular goal. • The collection of Use Cases should define all system behavior relevant to the actors to assure them that their goals will be carried out properly. • Any system behavior that is irrelevant to the actors should not be included in the use cases.

5. Developed for NASA TIWG Use Case • is a prose description of a system's behavior when interacting with the outside world. • is a technique for capturing functional requirements of business systems and, potentially, of an IT system to support the business system.

6. Developed for NASA TIWG Use Case • Must be documented (or it is useless) • Should be implemented (or it is not well scoped) • Is used to identify: objects ~ resources, processes, roles (aka actors), requirements, etc. • Should iterate with experts on wording and details at least once

7. Developed for NASA TIWG Roles and skill-sets needed • Facilitator *** (usual key skills, knows method) • Domain experts (literate, knows resources; data, applications, tools, etc.) • Modelers (to extract objects) • Software engineers (architecture, technology) • Scribe (to write everything down) • The social aspect is key - it is a team effort

8. Developed for NASA TIWG Roles and skill-sets • Facilitator – you may not be ready to play this role but you will need to ‘pretend’ • Engage some domain experts (they are literate, know the resources; data, applications, tools, etc. and you can share this role) • You will be the modeler (to extract objects, triples) • You may play the role of a software engineer (architecture, technology) but you can also ask someone for help with this • Write as much as you can down • Be prepared to be social - it is a team effort

9. Developed for NASA TIWG Note • Your roles and what is/ is not expected of you • Be prepared to draw on the white board • Keep your scoping in mind as you are proceeding • Identify objects, processes, actors/roles, organizations (or nouns, verbs, adjectives)

10. Developed for NASA TIWG Use Case Examples • Make a collection of *any data format* model run datasets available for internet access with web browsing to find suitable data and access to the data via Matlab.

11. Developed for NASA TIWG Use Case Examples: • Provide browse and quick look access to a broad variety of climate, weather and ocean data.

12. Developed for NASA TIWG Use Case Examples: • Install an OPeNDAP Hyrax server with THREDDS cataloging on the front-end to support netCDF and HDF4 data sets on the back-end and allow aggregation based on NcML and authentication of user access

13. Developed for NASA TIWG Use Case Examples: • Provide high-performance data transfer of specific climate model data products into the climate diagnostics and analysis tool (CDAT) for analysis, independent of their storage format, organization or location on the internet

14. Developed for NASA TIWG Use Case Examples: • A US 9th grade teacher is preparing a lesson plan aimed at getting students to learn more about the ‘northern lights’, addressing NSES content standards in earth science. The teacher wants the students to learn the scientific terminology, where the phenomena occurs and retrieve some data or graphics for a recent occurrence. The goal of the lesson plan is the engage students, using authentic data from the aurora, as part of an inquiry-based program.

15. Developed for NASA TIWG Elements of a Use Case • http://wiki.esipfed.org/index.php/SolutionsUseCase_Template • Start with the Plain Language Description • Short Definition • Purpose • Describe a scenario of expected use • Definition of Success

16. Developed for NASA TIWG Short Definition • Define the use case in plain sentences • Wherever possible avoid specifying technical solutions or implementation choices • Concentrate on the application aspects of the intended scenario • Also note when the use case may be applicable to more than one application area

17. Developed for NASA TIWG Purpose • A plain language description of • why this use case exists, • what the problem is to be solved, • what a successful outcome, and • what the impact may be. • Often termed the ‘business case’

18. Developed for NASA TIWG Scenario of expected use • A verbose (more detailed) description of one instance of a problem to be solved • what resources are generally needed (if known) • what a successful outcome and impact may be • who might be expected to do the work or provide the resources and • who might be expected to benefit from the work • List any performance or metric requirements for this use case and any other other considerations that a user would expect.

19. Developed for NASA TIWG Definition of Success • Quick test that would show whether or not the case is working as described.

20. Developed for NASA TIWG At this stage • Use case modelers should have a good sense of what the use case goal is. • They proceed on to the next stage to extract details. • They may contact other team members, e.g. domain experts, one-on-one for additional information.

21. Developed for NASA TIWG Formal Use Case Description • Use Case Identification • Revision Information • Definition • Successful Outcomes • Failure Outcomes

22. Developed for NASA TIWG General Diagrams • Schematic of Use case • How to draw diagrams: • Stick figures for actors (person or computer) • Boxes to denote resources • Arrows to denote process flow • Concept maps are a useful tool

23. Diagrams

24. Developed for NASA TIWG Use Case Examples: • A US 9th grade teacher is preparing a lesson plan aimed at getting students to learn more about the ‘northern lights’, addressing NSES content standards in earth science. The teacher wants the students to learn the scientific terminology, where the phenomena occurs and retrieve some data or graphics for a recent occurrence. The goal of the lesson plan is the engage students, using authentic data from the aurora, as part of an inquiry-based program.

25. Developed for NASA TIWG Schematic

26. Developed for NASA TIWG Use Case Elaboration • Actors • Primary Actors • Other Actors • Preconditions • Postconditions • Normal Flow (Process Model) • Alternative Flows • Special Functional Requirements • Extension Points

27. Developed for NASA TIWG Diagrams • Use Case Diagram • State Diagram • Activity Diagram • Other Diagrams

28. Developed for NASA TIWG Non-functional requirements • Performance • Reliability • Scalability • Usability • Security • Other Non-functional Requirements

29. Developed for NASA TIWG Alternate form • Use case name • Summary • Activity diagram • Preconditions in tabular form • Triggers • Basic flow • Alternate flow • Post conditions

30. Developed for NASA TIWG Preconditions - data/model

31. Developed for NASA TIWG Preconditions - event/application

32. Developed for NASA TIWG Which format to use? • Short (in document) format for: • Exploratory phase of a project where you want to collect a lot of use cases • An example for others to use • Including in a proposal • In an assignment (hint) • Long (on wiki) format for: • Detailed documentation of the use case • Life cycle documentation for implementation • Asynchronous/ collaborative development • Part of a group assignment (another hint)

33. Scoping Focus initially on: Core functionality What it takes to implement the use case, resist early generalizations May (will) have to iterate on use case and requirements Acknowledge other important issues such as: Required vs. optional Non-functional requirements Available personnel (skills) and resources

34. Actors • The initial analysis will often have many human actors • Begin to see where these can be replaced with machine actors – may require additional encoding • If you are doing this in a team, take steps to ensure that actors know their role and what inputs, outputs and preconditions are expected of them • Often, you may be able to ‘run’ the use case (really the model) before you build anything

35. Developed for NASA TIWG Actors • Real people (round heads) and computers (block heads) • E.g. Data provider, end-user, data manager, alert service • Primary – initiate (act on) • Secondary – respond (acted upon)

36. Developed for NASA TIWG What’s a pre-condition? • defines all the conditions that must be true (i.e., describes the state of the system) for the trigger to meaningfully cause the initiation of the use case.

37. Preconditions • Often the preconditions are very syntactic and you may not understand how they fit in the implementation • Some level of modeling of these preconditions may be required (often this will not be in your first pass encoding which focuses on the main process flow, goal, description, etc.) • Beware of using another entities data and services: policies, access rights, registration, and ‘cost’

38. Developed for NASA TIWG What’s a post-condition? • describes what the change in state of the system will be after the use case completes. Post-conditions are guaranteed to be true when the use case ends.

39. Developed for NASA TIWG Success scenarios • A re-statement of how the use case via its flows and actors and resources results in achieving the result • Describe artifacts produced • Describe impacts and metric values

40. Developed for NASA TIWG Failure scenarios • A statement of how the use case via its flows and actors and resources did not result in achieving the result • Describe role of actors in failure • Describe role of resources in failure • Describe what artifacts were and were not produced • Describe impacts of failure and any metric values

41. Developed for NASA TIWG Normal (process) flows • A basis step of (usually) distinct steps that result when the use case is triggers (commences) • Steps are often separated by actor intervention or represent modular parts of the flow (can encapsulate activities) • Can have loops • Should end with the final goal achieved

42. Process flow • Each element in the process flow usually denotes a distinct stage in what will need to be implemented • Often, actors mediate the process flow • Consider the activity diagram (and often a state diagram) as a means to turn the written process flow into a visual one that your experts can review • Make sure the artifacts and services have an entry in the resources section • This is often the time you may do some searching (no, not soul searching – web searching…)

43. Developed for NASA TIWG Alternate (process) flows • Variations from the main flow, often invoked by valid but non-usual (or rules) • Activity diagrams are useful in representing this part of the document • Do not usually represent exceptions/ error flows • Can often help to identify general patterns in the use case via similarities with the normal flow • While many are possible, usually only include one - illustrative

44. Developed for NASA TIWG Functional/ non-functional • (from Wikipedia): requirements which specify criteria that can be used to judge the operation of a system, rather than specific behaviors. • This should be contrasted with functional requirements that specify specific behavior or functions. • In general, functional requirements define what a system is supposed to do whereas non-functional requirements define how a system is supposed to be.

45. Developed for NASA TIWG Functional/ non-functional • (from Wikipedia): Non-functional requirements are often called qualities of a system. Other terms for non-functional requirements are "constraints", "quality attributes", "quality goals" and "quality of service requirements". • Qualities, (non-functional requirements), can be divided into two main categories. • Execution qualities, such as security and usability, are observable at run time. • Evolution qualities, such as testability, maintainability, extensibility and scalability, are embodied in the static structure of the software system.

46. Artifacts • Add artifacts that the use case generates to the resources list in the table • It is often useful to record which artifacts are critical and which are of secondary importance • Be thinking of provenance and the way these were produced, i.e. what went into them and produce suitable metadata or annotations • Engage the actors to determine the names of these artifacts and who should have responsibility for them (usually you want the actors to have responsibility for evolution)

47. Reviewing the resources • Apart from the artifacts and actor resources, you may find gaps • Define/ find the authoritative sources for data, information, metadata, configuration • Your encodings can also be a resource, make it a first class citizen, e.g. on the web give it a namespace and a URI • Sometimes, a test-bed with local data is very useful as you start the implementation process, i.e. pull the data, maybe even implement their service (database, etc.)

48. Developed for NASA TIWG When someone asks: “What is your use case”? • Treat it like your ‘elevator pitch’ • Know them, especially the ones you have implemented • Tell them how you used it to develop a solution FOR use

49. If you have not developed one • Try reverse engineering • Start with a personal example e.g. balancing your checkbook

50. Developed for NASA TIWG Resources • http://alistair.cockburn.us/index.php/Use_cases,_ten_years_later • http://www.digilife.be/quickreferences/pt/functional%20requirements%20and%20use%20cases.pdf • http://alistair.cockburn.us/index.php/Resources_for_writing_use_cases • http://alistair.cockburn.us/Usecasesintheoryandpractice180.ppt • http://alistair.cockburn.us/Agileusecases1dy.ppt • http://alistair.cockburn.us/index.php/Structuring_use_cases_with_goals • http://www.foruse.com/publications/bibliographies/usecases.htm • http://en.wikipedia.org/wiki/Use_case • http://www.ddj.com/dept/architect/184414701 • Omnigraffle (Mac) www.omnigroup.com/applications/omnigraffle/or • Cmap http://cmap.ihmc.us/ • wiki template