COP 4020 Oz Programming Language Presentation Chris Savela Zak Roessler

COP 4020Oz Programming Language

Presentation

Chris Savela

Zak Roessler

COP 4020: Oz Programming Language page 2

Oz: Table of Contents

History of Oz Origins of Oz Foundations of Oz Versions of Oz Applications of Oz Oz Language and Basics Programming Conclusion


Oz: History

History of Oz Oz was conceived in 1991 by Gert Smolka at Saarland University in

Sweden

Development continued in collaboration with Seif Haridi and Peter van Roy at Swedish Institute of Computer Science

Since 1999, Oz has been continually developed by an international group, the Mozart Consortium, which originally consisted of Saarland University, the Swedish Institute of Computer Science, and the Université catholique de Louvain


Oz: History

History of Oz In 2005, the responsibility for managing Mozart development was

transferred to a core group, the Mozart Board, with the express purpose of opening Mozart development to a larger community.

The Mozart Programming System is the primary implementation of Oz. It is released with an open source license by the Mozart Consortium. Mozart has been ported to different flavors of Unix, FreeBSD, Linux, Microsoft Windows, and Mac OS X.


Oz: Origins of Oz

Oz is an experimental language and draws from experience in programming languages such as: Prolog - general purpose logic programming language associated

with artificial intelligence and computational linguistics

Erland - is a general-purpose concurrent programming language

Lisp/Scheme - is a functional programming language and one of the two main dialects of the programming language Lisp


Oz: Foundations

Foundations of Oz Oz combines the most important features of object-oriented

programming, by providing state, abstract data types, classes, objects, and inheritance

Oz provides the most important features of logic programming and constraint programming by providing logic variables, disjunctive constructs, and programmable search strategies.


Oz: Foundations

Foundations of Oz Oz provides the most important features of functional programming

by providing composition syntax, first-class procedures, and lexical scoping. Every entity in Oz is first class including procedures, threads, classes, methods, and objects.

A programming language is said to have first-class functions if it treats functions as first-class citizens. Specifically, this means that the language supports passing functions as arguments to other functions, returning them as the values from other functions, and assigning them to variables or storing them in data structures.


Oz: Foundations

Foundations of Oz Oz is a concurrent language where users can create dynamically

any number of sequential threads that can interact with each other. Each thread in Oz is a dataflow thread

Executing a statement in Oz proceeds only when all real dataflow dependencies on the variables involved are resolved.


Oz: Foundations

Foundations of Oz Using the Mozart development environment for Oz one can create

a distributed environment for Oz computations.

Multiple Oz sites can connect together and automatically behave like a single Oz computation sharing variables, objects and classes and procedures.

Sites disconnect automatically when references between entities on different sites cease to exist.

In a distributed environment Oz provides language security.


Oz: Versions of Oz

Oz 1 Supported a fine-grained notion of concurrency where each

statement could potentially be executed concurrently.

Fine-grained model similar to actor model

This model was theoretically appealing, but it had drawbacks: Very hard for the programmer to control resources of the application

Very hard to debug

Object model was unnecessarily awkward


Oz: Versions of Oz

Oz 2 Introduced a thread based concurrency model with explicit creation

of threads to remedy issues with concurrency from Oz 1.

A powerful new object system was introduced that included traditional exception handling.

Also constraint solving and search capabilities were enhanced


Oz: Versions of Oz

Oz 3 – Current version Conservatively extends Oz 2 two new concepts:

Functors Software components that specify a module in terms of other module needs Supports incremental construction of program components that may be

addressed over the internet by URL’s

Futures Logic variable that can be read but not written Allows safe dataflow synchronization over the internet


Oz: Applications

Applications of Oz Teaching language

Developed as a way to teach programming by gradually introducing new concepts and showing what they are good for.

To show how all major programming paradigms fit in a uniform framework.

Simulations The imitation of the operation of a real-world process or system over time


Oz: Applications

Applications of Oz Multi-Agent Systems

System composed of multiple interacting intelligent agents within an environment. Multi-agent systems can be used to solve problems that are difficult or impossible

for an individual agent or a monolithic system to solve

Natural Language Processing The process of a computer extracting meaningful information from natural

language input and/or producing natural language output.

Virtual Reality Applies to computer-simulated environments that can simulate physical presence

in places in the real world, as well as in imaginary worlds


Oz: Language Basics

Language Basics Oz language referred to as syntactic sugar

Syntactic Sugar refers to syntax within a programming language that is designed to make things easier to read or to express.

It makes the language "sweeter" for humans to use: things can be expressed more clearly, more concisely, or in an alternative style that some may prefer


Oz: Language Basics

Language Basics Oz is referred to as a small kernel language

Oz execution model Consist of dataflow threads observing a shared store.

Threads contain statement sequences and communicate through a shared references in the store.

A thread is dataflow if it only executes its next statement when all the values the statement needs are available.

If a statement needs a value that is not available yet, the thread will block until it can access that value.


Oz: Language Basics

Oz Data Availability Implemented using logical variables

The shared store is not physical memory

The shared store is an abstract store which only allows operations that are legal for the entities involved

There is no direct way to inspect the internal representations of entities


Oz: Language Basics

OZ data store can contain Bound and unbound logic variables

Cells which are mutable pointers which points to variables

Procedures

Variables can reference the names of procedures and cells

Variables can be bound to any entity, including other variables

Variable and produced stores are monotonic, i.e., information can only be added to them, not changed or removed.


Oz: Base Environment

A mapping of identifiers to values Organized in modules Available via field selection.





Module Value

Contains procedures that con operate on many types {Value. ‘=‘ X Y}

Unifies {Value ‘==‘ X Y ? B }

Equality {Value. ‘\\=‘ X Y ? B }

Not Equal



Module Numbers

Contains procedures operating on numbers {Number.is +X ? B }

IsNumber {Number. ‘+’ +FI1 +FI2 ? FI3 }

Sum {Number.pow +FI1 +FI2 ? FI3 }

FI1 to power of FI2



Module Floats

Contains procedures operating on floats {Float.is +X ? B }

IsFloat {Float. ‘/’ +FI +F2 ? F3 }

F1 divided by F2 {Float.sqrt + F1 ? F2 }

Square Root



Module Functor

Support for module specification Expression that specifies components of a module



Type Oz is dynamically typed

A variables type and value are unknown until it is bound to an Oz value. Shares a common structure

Float < Number < Value

Array < Chunk < Value


Oz: Programming

Basics Computations performed by a sequential process, executing one

statement after another. Process is a thread


Oz: Programming

Basics Simple programs

local X Y Z in s end Execute s in the scope of X Y Z

Another

local I F in

I = 5

F = 5.5

{Browse [ I F C] }

end


Oz: Programming

Basics - control If Statement

if B then S1 else S2 Procedure

Can be defined, passed as argument or stored in a record Unique

proc {P X1 … Xn} S end


Oz: Programming

Creating a program that copies files First things first

Download and intall Oz environment Compile with ozc.exe Run with ozengine.exe


Oz: Programming functor

<Module import><Functor Body>

end



import Application Open<Functor Body>

end



import Application Opendefine

<Argument process>Status = try

<Opening input and output files>in <Copying input to output file>catch _ then 1end

<Terminating the application>end




Args = {Application.getargs record(‘in’ (single type:string)‘out’ (single type:string))}

Status = try <Opening input and output files>in <Copying input to output file>catch _ then 1end






Status = try I = {new Open.file init(source: Args.’in’)} O= {new Open file init(name Args. ‘out’

flags:[write create truncate])}in <Copying input to output file>catch _ then 1end







flags:[write create truncate])}in local proc {copy} S={I read(list::$} in if S\=“” then

{O write(vs:S)} {copy} end

end in {copy} endcatch _ then 1end







flags:[write create truncate])}in local proc {copy} S={I read(list::$} in if S\=“” then

{O write(vs:S)} {copy} end

end in {copy} endcatch _ then 1end

{Application.exit Status}end


Oz: Programming

File A File B


Oz: Conclusions

How do programming languages get their power? Traditional languages use libraries to proivde extra functionality.

The library approach soon hits a brick wall by the limits of its underlying language.

Oz has been designed such that has a small number of concepts can be combined in many ways. The designers of Oz believe the concept approach can go much further and have used this in their design.

Oz provides a large set of basic concepts and allows the developers to choose the paradigm needed to solve the problem.


Oz: Conclusions

Flexibility comes with a price. The execution of OZ is very slow compared to other languages. On a set of benchmarks it about 50 times slower then that of gcc compiler for C.


Resources

http://en.wikipedia.org/wiki/Oz_(programming_language) http://en.wikipedia.org/wiki/Prolog http://en.wikipedia.org/wiki/Erlang_(programming_language) http://en.wikipedia.org/wiki/Scheme_programming_language http://www.mozart-oz.org/documentation/tutorial/ http://www.mozart-oz.org/documentation/tutorial/node1.html#label2 http://www.mozart-oz.org/papers/abstracts/volume1000.html

http://en.wikipedia.org/wiki/Oz_(programming_language)

http://en.wikipedia.org/wiki/Prolog

http://en.wikipedia.org/wiki/Prolog

http://en.wikipedia.org/wiki/Erlang_(programming_language

http://en.wikipedia.org/wiki/Scheme_programming_language

http://www.mozart-oz.org/documentation/tutorial/

http://www.mozart-oz.org/documentation/tutorial/

http://www.mozart-oz.org/documentation/tutorial/node1.html

http://www.mozart-oz.org/documentation/tutorial/node1.html

http://www.mozart-oz.org/papers/abstracts/volume1000.html

http://www.mozart-oz.org/papers/abstracts/volume1000.html

COP 4020Oz Programming Language

Presentation

Chris Savela

Zak Roessler

Documents

COP 4020 Oz Programming Language Presentation Chris Savela Zak Roessler