R R R CSE870: Advanced Software Engineering: Extending and Using UML (Cheng, Sp2003) Supplementary: Using and Extending UML

R R R CSE870: Advanced Software Engineering: Extending and Using UML (Cheng, Sp2003) Extensibility Mechanisms Stereotypes Tagged Values Constraints ActionQueue > {version = 3.2} add(a: Action) remove(n: Integer) {add runs in O(1) time}

R R R CSE870: Advanced Software Engineering: Extending and Using UML (Cheng, Sp2003) Stereotypes Extends the UML vocabulary Create new building blocks derived from existing ones, –specific to problem domain –Example: Sensors for embedded systems, > thermometer temp read > Voltage meter volt read

R R R CSE870: Advanced Software Engineering: Extending and Using UML (Cheng, Sp2003) Tagged Values Extends properties of UML building block Create new information in that element’s spec Example: {version, author values for Software Class} > Voltage meter volt read {reader=J. Smith}

R R R CSE870: Advanced Software Engineering: Extending and Using UML (Cheng, Sp2003) Constraint Extends the semantics of a UML building block Add new rules or modify existing ones –Example: {ordered constraint on a add operation for a Queue} > Voltage meter volt read {reader=J. Smith} {read before thermostat check}

R R R CSE870: Advanced Software Engineering: Extending and Using UML (Cheng, Sp2003) Interface Interface: collection of operations that specify a service of a class or component –Externally visible behavior of that element –Set of operation specs (signatures) –Not a set of operation implementations

R R R CSE870: Advanced Software Engineering: Extending and Using UML (Cheng, Sp2003) Interface Example Interface specifies desired behavior of an abstraction independent of implementation Specifies contract May also create stereotype to further define behavior –No attributes –Only operations (visibility, concurrency, stereotypes, etc.) Wordsmith.dll ISpell IThesaurus IUnknown > URLStreamHandler openConnection() Parse URL() setURL() toExternalForm() Operations

R R R CSE870: Advanced Software Engineering: Extending and Using UML (Cheng, Sp2003) Dependency Relationship Definition: –some set of model elements requires presence of another set of model elements –for semantic completeness or correctness Examples: – >: between type and class – >: analysis class and design class – >: source class creates a target class instance – >: permission of one pkg to access public elements of another – >: reln between parameterized model elt with formal parameter list and that model elt bound to actual parameters. (e.g., templates in C++)

R R R CSE870: Advanced Software Engineering: Extending and Using UML (Cheng, Sp2003) Dependency Example Queue Basetype, size Queue String, 400 Integer Queue Explicit Parameterization Formal parameter list Actual parameter list

R R R CSE870: Advanced Software Engineering: Extending and Using UML (Cheng, Sp2003) Metamodels

R R R CSE870: Advanced Software Engineering: Extending and Using UML (Cheng, Sp2003) Class Diagram Metamodel

R R R CSE870: Advanced Software Engineering: Extending and Using UML (Cheng, Sp2003) Object Model Creation Tips –understand the problem –keep it simple at first, then refine later –choose class names carefully –try to have only binary relations –do not worry about multiplicities on first draft –do not feel you have to use all constructs –concentrate on WHAT –document reasons behind the model –refine until complete and correct

R R R CSE870: Advanced Software Engineering: Extending and Using UML (Cheng, Sp2003) Dynamic Model Creation Tips –only construct state diagrams for object classes with meaningful dynamic behavior –verify consistency between diagrams for shared events –use scenarios to begin the construction of diagrams –let application decide on granularity and distinguish between actions and activities –make use of entry and exit actions for multiple transitions –use nested states to improve understanding/readability –distinguish state diagrams for super and subclasses –watch for race conditions in the diagrams

R R R CSE870: Advanced Software Engineering: Extending and Using UML (Cheng, Sp2003) Approaching a Problem Where do we start? How do we proceed?

R R R CSE870: Advanced Software Engineering: Extending and Using UML (Cheng, Sp2003) Where Do We Start? Start with the requirements –Capture your goals and possible constraints –Environmental assumptions Use-case analysis to better understand your requirements –Find actors and a first round of use-cases Start conceptual modeling –Conceptual class diagram –Interaction diagrams to clarify use-cases –Activity diagrams to understand major processing Requirements Elicitation and Analysis

R R R CSE870: Advanced Software Engineering: Extending and Using UML (Cheng, Sp2003) How Do We Continue? Refine use-cases –Possibly some “real” use-cases Using interface mockups Refine (or restructure) your class diagram –Based on your hardware architecture For instance, client server Refine and expand your dynamic model –Until you are comfortable that you understand the required behavior Identify most operations and attributes High-Level Design

R R R CSE870: Advanced Software Engineering: Extending and Using UML (Cheng, Sp2003) How Do We Wrap Up? Refine the class diagram based on platform and language properties –Navigability, public, private, etc –Class libraries Identify all operations –Not the trivial get, set, etc. Write a contract for each operation Define a collection of invariants for each class Implement Detailed Design and Implementation

R R R CSE870: Advanced Software Engineering: Extending and Using UML (Cheng, Sp2003) Why is requirements analysis difficult? Communication: misunderstandings between the customer and the analyst –Analyst doesn’t understand the domain –Customer doesn’t understand alternatives and trade-offs Problem complexity –Inconsistencies in problem statement –Omissions/incompleteness in problem statement –Inappropriate detail in problem statement

R R R CSE870: Advanced Software Engineering: Extending and Using UML (Cheng, Sp2003) Why is requirements analysis difficult? Need to accommodate change –Hard to predict change –Hard to plan for change –Hard to predict the impact of change

R R R CSE870: Advanced Software Engineering: Extending and Using UML (Cheng, Sp2003) First Law of Software Engineering “ No matter where you are in the system lifecycle, the system will change, and the desire to change it will persist throughout the lifecycle.”

R R R CSE870: Advanced Software Engineering: Extending and Using UML (Cheng, Sp2003) Reasons for changing requirements Poor communication Inaccurate requirements analysis Failure to consider alternatives New users New customer goals New customer environment New technology Competition Software is seen as malleable Changes made after the requirements are approved increase cost and schedule

R R R CSE870: Advanced Software Engineering: Extending and Using UML (Cheng, Sp2003) Requirements Products Specification document –Agreement between customer and developer –Validation criteria for software Preliminary users manual Prototype –If user interaction is important –If resources are available Review by customer and developer –Iteration is almost always required

R R R CSE870: Advanced Software Engineering: Extending and Using UML (Cheng, Sp2003) Analysis: Steps to follow Obtain a problem statement Develop use cases (depict scenarios of use) Build an object model and data dictionary Develop a dynamic model –state and sequence diagrams Verify, iterate, and refine the models Produce analysis document

R R R CSE870: Advanced Software Engineering: Extending and Using UML (Cheng, Sp2003) Use Cases High-level overview of system use Identify scenarios of usage Identify actors of the system: –External entities (e.g., users, systems, etc.) Identify system activities Draw connections between actors and activities Identify dependencies between activities (i.e., extends, uses)

R R R CSE870: Advanced Software Engineering: Extending and Using UML (Cheng, Sp2003) Analysis: Object Model Organization of system into classes connected by associations –Shows the static structure –Organizes and decomposes system into more manageable subsystems –Describes real world classes and relationships

R R R CSE870: Advanced Software Engineering: Extending and Using UML (Cheng, Sp2003) Analysis: Object Model Object model precedes the dynamic model because –static structure is usually better defined –less dependent on details –more stable as the system evolves

R R R CSE870: Advanced Software Engineering: Extending and Using UML (Cheng, Sp2003) Analysis: Object Model Information comes from –The problem statement and use cases –Expert knowledge of the application domain Interviews with customer Consultation with experts Outside research performed by analyst –General knowledge of the real world

R R R CSE870: Advanced Software Engineering: Extending and Using UML (Cheng, Sp2003) Object Model: Steps to follow Identify classes and associations –nouns and verbs in a problem description Create data dictionary entry for each Add attributes Combine and organize classes using inheritance

R R R CSE870: Advanced Software Engineering: Extending and Using UML (Cheng, Sp2003) Analysis: Dynamic model Shows the time dependent behavior of the system and the objects in it Expressed in terms of –states of objects and activities in states – events and actions State diagram summarizes permissible event sequences for objects with important dynamic behavior

R R R CSE870: Advanced Software Engineering: Extending and Using UML (Cheng, Sp2003) Dynamic Model: Steps to follow Use cases provide scenarios of typical interaction sequences Identify events between objects (Sequence Diagram) Prepare an event trace for each scenario Build state diagrams Match events between objects to verify consistency

R R R CSE870: Advanced Software Engineering: Extending and Using UML (Cheng, Sp2003) Analysis: Iteration Analysis model will require multiple passes to complete Look for inconsistencies and revise Look for omissions/vagueness and revise Validate the final model with the customer