1 presentation and tool by jason kealey [email protected] automatic conversion of use cases to use...

1

Presentation and tool by

Jason [email protected]

Automatic conversion of

Use Cases to Use Case Maps

2Jason Kealey, [email protected], http://www.softwareengineering.ca/jucmnav

Textual Use Cases

• Sequence of steps representing a high level view of the interactions between a system under discussion (SuD) and other entities (actors, users).

• Black-box view of a system

• Used early in the development cycle

• Written in natural language


Why are Use Cases Important?

• Requirements and use cases written in natural language are easily understood by all stakeholders.

• Use Cases are a good starting point when refining the scope and functionality required by the client

• Formal languages cannot be accepted as a contract for a software system [Schwitter and Fuchs, 1996]


What are the drawbacks?

• Natural language is ambiguous

• Informal languages can’t verify completeness and consistency automatically.

• Use cases are (usually) no longer maintained once code has been written. The maintenance effort seems too great and doesn’t appear to offer a good return on investment.


Key idea: simplified English

• Key idea: use a subset of English in use case steps. – References to Writing Effective Use Cases and other

books/papers to validate the simplified English to be used.

– Related work: Controlled languages (AECMA Simplified English: aviation industry standard)

• SVDPI pattern:– Subject – verb - direct object – preposition - indirect

object– Example: System sends a new password to the user


Use Case Step

• Three different action types – Communication between an actor and SuD

• Operation request received by SuD from actor (1)– User requests the detailed item description

• Operation request sent by SuD to actor (2)– System sends a new password to the user

– An internal action (SuD) (3)– System validates the user’s credit card number

• A use case step can also represent a redirection to another step


How to find the step’s action type?

• In an SVDPI sentence, the top of the parse tree should show S -> NP VP

• The NP is the subject. If it represents an actor, we have an operation request received by SuD from actor (1).

• Distinguish between (2) and (3) by looking at the indirect object. The actor must not be in possessive case.


Estimating Method Call (1)

• Find the principal verb – Headword of the topmost VP, exception made

of padding verbs.

– If we have a padding verbs (ask/be/select to/choose to), use the next verb.

– Example: System asks the Supervisor to validate the seller

• use validate instead of asks


Estimating Method Call (2)

• Find the representative object– First basic noun phrase subordinate to the

principal verb.

– We do not consider phrases already used as the subject and the indirect object.

– Example: Seller submits item description• Representative object: Item description


Special Actions

• Termination actions: – Use case aborts/terminates/ends

• Goto actions:– Resume with step 2– Retry step 1

• Very simple syntax, will not cover here.


Conditions of Extensions and Variations

• A simple condition must adhere to the following syntax.– [determinant] entity verb value

• Possible determinants are: a, an, the.• Possible verbs are: is, isn’t, is not, are, aren’t, are not, has, hasn’t, has

not, have, haven’t, have not.

• A value may be one of the possible values of the condition entity, or specified as a general comparison. – For possible values, the sequence of words used to refer to the

value must be declared as a possible value of the entity in the domain model.

– For general comparisons, the syntax for value specification must adhere to the following: comparator value.

• Possible comparators are: >, <, =, <=, >=, <>, greater than, less than, equal to, different to, greater or equal to, less or equal to.

• A complex condition is a negation, a conjunction or a disjunction of conditions.– [(NO|NOT)] condition ((AND|OR) condition)*

(From UCEd documentation)


UCEd: Use Case Editor

• A tool that uses simple English to write use cases

• Eclipse-based tool

• Validates the use cases with a domain model

• Can convert use cases into state machines

• Can execute scenarios on these state machines


Example UCEd Use Case


Quick note on Use Case Diagrams


Use Case Maps

• A graphical notation to express scenarios running through architectural entities.

• Standardized by the International Telecommunication Union

• Part of the User Requirements Notation (URN)

• jUCMNav is an Eclipse-based UCM editor


Example Use Case Map


Research Goals

• Study the NLP related to understanding the different Use Cases constructs.

• Express improvements to be made to the NLP tool used in UCEd.

• Define mappings between Use Case concepts and Use Case Map concepts.

• Prototype the conversion utility from UCEd use cases to jUCMNav Use Case Maps.


Concepts by example – Main Path

Title: General ScenarioPrecondition: jUCMNav is not UCM loadedPostcondition: jUCMNav is UCM loadedSteps:1. User Jason clicks import button2. jUCMNav GUI displays file list3. User Jason selects file4. jUCMNav ImportExport forwards request5. UCEd loads Use Case6. jUCMNav ImportExport UC2UCM converts Use Case into Use Case Map7. jUCMNav loads UCM8. jUCMNav GUI displays UCM


Quick Note – Auto layout• jUCMNav has an auto layout feature, currently

only a prototype. • The examples seen here are touched up versions

of these generated UCMs.


Concepts by example – Alternatives

Title: General ScenarioPrecondition: jUCMNav is not UCM loadedPostcondition: jUCMNav is UCM loaded1. User Jason clicks import button2. jUCMNav GUI displays file list3. User Jason selects file4. UCEd loads Use Case5. jUCMNav ImportExport UC2UCM converts UC into UCM6. jUCMNav loads UCM7. jUCMNav GUI displays UCM3. a. User file is not found3. a. 1. Goto step 24. a. UCEd Use Case is not valid4. a. 1. jUCMNav GUI displays error message


Concepts by example – Inclusion

Title: General Scenario1. User Jason clicks import button2. jUCMNav GUI displays file list3. User Jason selects file4. include Load Use Case5. jUCMNav ImportExport UC2UCM converts UC into UCM6. jUCMNav loads UCM7. jUCMNav GUI displays UCM

Title: Load Use Case1. UCEd loads Use Case2. IF UCEd Use Case is not valid THEN jUCMNav GUI displays error message


Concepts by example – Extensions

Title: General ScenarioPrecondition: jUCMNav is not UCM loadedPostcondition: jUCMNav is UCM loaded1. User Jason clicks import button2. User Jason selects file3. include Load Use Case4. jUCMNav ImportExport UC2UCM converts UC into UCM5. jUCMNav loads UCMExtensionPoint==> loaded6. jUCMNav GUI displays UCM

Title: LoggingPART 1. At Extension Point loaded1. jUCMNav logs usage


Concepts by example – Timing

Title: General ScenarioPrimary Actor: User Jason1. User Jason clicks import button2. User Jason selects file3. BEFORE 60 sec jUCMNav ImportExport UC2UCM converts UC into UCM4. jUCMNav loads UCM5. jUCMNav GUI displays UCM2. a. AFTER 60 sec2. a. 1. jUCMNav GUI displays error message


Possible UCEd NLP Improvements

• Improve the domain extractor by using parse trees instead of BNF grammar.

• Review use of determinants in conditions.• Simplify notation required to reference components in

use case steps.• Support scenario termination and extension

abortion.• Use indirect object to refine communication model.• Allow padding verbs as discussed previously• (UCEd also needs a major usability overhaul)


Future work• Current import limitations

– Doesn’t create stub InBindings/OutBindings.– Can’t jump to later step.

• Illegal in UCEd, but could be implemented.– Support for Any * alternatives– Support for operation effects– jUCMNav currently does not support scenarios and has

limited support for time.• Causes many issues concerning conflicting alternatives,

especially with time issues.


Conclusion and references

• D. Amyot, Introduction to the User Requirements Notation: Learning by Example, Computer Networks, 42(3), June 2003, 285-301.

– http://www.usecasemaps.org/pub/ComNet03.pdf

• D. Amyot and G. Mussbacher, “On the Extension of UML with Use Case Maps Concepts”, 2000, 3rd International Conference on the Unified Modeling Language, York, UK, October 2000. LNCS 1939, 16-31

– http://www.usecasemaps.org/pub/uml2000.pdf

• J. Kealey, E. Tremblay, J.-P. Daigle, J. McManus, and O. Clift-Noël, “jUCMNav: une nouvelle plateforme ouverte pour l'édition et l'analyse de modèles UCM“, Actes du 5ième colloque sur les Nouvelles Technologies de la Répartition (NOTERE 2005), Gatineau, Canada, août 2005, 215-222.

– http://www.site.uottawa.ca/~damyot/pub/notere05.pdf

• V. Mencl, “Deriving Behavior Specifications from Textual Use Cases”, Proceedings of Workshop on Intelligent Technologies for Software Engineering (WITSE04), Linz, Austria, September 2005, 331-341,

– http://nenya.ms.mff.cuni.cz/publications/Mencl-DerivingBehSpec-WITSE04.pdf

• S. Somé, “Beyond Scenarios: Generating State Models from Use Cases”, ICSE 2002 Workshop Scenarios and state machines: models, algorithms, and tools, May 2002.

– http://www.site.uottawa.ca/~ssome/publis/ICSE02_Scenario_Workshop.pdf


Open questions

• Is this a success?– I think that given the most common uses of UC, the

transformation is good. (I have no references for this)

• Is this useful? – I think that in its current state it is not.

• Need to find industry leader UC editors, if they exist.• Even then, still not hooked in properly with existing development

processes.

– Would the generation of UC from UCM be an interesting addition?

• I think so. Keeping both in synch would be even better, but 100% compatibility is unreachable.

1 presentation and tool by jason kealey [email protected] automatic conversion of use cases to use...

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