Marine Biology Simulation Part I Introduction Dung Zung

Marine Biology Simulation Part I: Introduction Dung “Zung” Nguyen Mathias Ricken Stephen Wong Teach. Java 2004! June 25, 2004

The Role of Programming Important skill Should be taught early in a student’s career Usually taught imperative-first Concentrates on language elements like expressions, operators, functions, pointers…

Problems Teaching Imperative-First Focus on syntactical elements Exercises too simple to be motivating Too little emphasis on design Biased against students without prior knowledge

Object-Orientation Beneficial to software quality Correct, robust, flexible, and extensible Extensively covers software design Examples are more challenging and motivating Usually considered “advanced concept”

Assignments have to be complex Highlight benefits of object-orientation Large design portion Find proper abstractions, variants / invariants Solve family of problems Challenge to find suitable assignments Example: Marine Biology Simulation

AP Marine Biology Simulation Case studies in AP curriculum since 1994 Argument: “Some good reasons to use a case study in AP Computer Science include: • Working with a program of significant length • Thinking through issues of good program design • Learning from an expert programmer” (AP Marine Biology Simulation Case Study – Teacher’s Manual)

AP Marine Biology Simulation Goal: “Through the AP Marine Biology Simulation Case Study, the strategies, vocabulary, and techniques of object-oriented design will be emphasized. ” (AP Marine Biology Simulation Case Study – Teacher’s Manual) Shortcomings Improper abstractions, incorrect delineation of responsibilities not robust Tight coupling not flexible and extensible

AP Marine Biology Simulation Demo

AP Marine Biology Simulation a few pitfalls. . . Insecure architecture Replicated data Unenforceable contracts Limited extensibility Key issue: Tight Coupling

And On Which I know some notisthe where not global Where Think same the ISimple. coordinate am: am same as. I? right here as here either. here grid? . Do I know my own coordinates? Does anyone else know my coordinates? Should I know anyone else’s coordinates? Do I really care where Greenwhich is? X X X Latitude = 29. 65 Longitude = 95. 28

The local is an Each fish environment has its own local indirectionenvironment layer between the fish and the global environment. X X X

Fish and their Environment A fish has a local environment Local environment communicates with global environment but fish do not. The local environment provides services to the fish The local environment is instantiated by the The local Factory Method global environment does Design Pattern NOT provide x-y coordinates!

Send a. Icommands message totothe The Unblocked appropriate Blocked fish Can Aresponds Fish’s move case command Dilemma forward? command accordingly! command is selected Send localenvironment! local Unblocked! Blocked! X

Local environment makes a The If desired, appropriate Movefish command applies Or… command sent move is tocommand selected fish move command X Unblocked! Move Blocked!Command A fish can ONLY move as prescribed by its environment!

A fish does not need to know its x-y coordinate! A fish does not need to know “how” to move! A fish is decoupled from the global environment!

Fish-Environment Interaction Simple. Fish Class Delegate to the local environment _local. Env. try. Move. Fwd(this, new ILambda() { public Object apply(Object not. Used) { turn. Right(Math. PI); Command return null; to execute if blocked } }, new ILambda() { public Object apply(Object move. Cmd) { ((ILambda)move. Cmd). apply(null); return null; Command to execute if } unblocked });

Fish-Environment Interaction Make local Depending on Local. Environment whether the. Class new local environment is empty or not… environment in the direction the fish wants to move … either make a command that actually moves the fish… Code is used in a class assignment and has been removed … and execute the unblocked command … or execute the blocked command

Design Benefits Decoupled, abstract design Enhanced capabilities Replaceable environments Different fish Robustness

Rice Marine Biology Simulation Demo

The Culmination of a Unified OO Pedagogy ~ end of 2 nd semester. MBS Unit Tests Design Patterns Polymorphism Abstract Structure and Behavior

Problems Using This in AP Classes Defined curriculum Students must perform well in exams Teach what exams require Current curriculum disagrees with our approach Rice MBS is for university-level classes

Results Objects-first is programming for everyone Addresses problems of imperative-first Focus on design Motivating assignments Not biased against Lack of experience Gender Declared Major Year in School SAT Scores AP curriculum will hopefully change

Future Work Make simulation guarantee progress Prevent one fish from blocking others Extra credit competition using MBS Game of life, outbreed other species? Study MBS along several cognitive dimensions Improve assignment quality