Parser G ra p h Ob jectSage LanguageRe p o sito ry

Programclass CClass1 {public: void Method1();private: int Field1;};

Te xt

The ObjectSage:Building object models by

textual descriptions

Andrew Breslavbreslav@rain.ifmo.ru

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Software CASE toolsstate-of-the-art

• UML modeling• Partially automatic code generation• Refactoring browsers (occasionally)• Context-sensitive search and filters• Visual interface building• Business logic support

Design and coding only – no analysis

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Abbott’s method

In 1983 Russel J. Abbott formulated a method of program development by informal English descriptions.

Basics:• English syntax contains enough

information to consider some abstract to be an object, attribute or method.

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Abbott’s method

• A subject (syntactical) is considered to be an object.

• A predicate is considered to be a method.• All the modifiers are considered to be

attributes of objects or parameters of methods.

The suggested approach helps to perform object-oriented analysis.

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Abbott’s problem

«Although the process we follow in formalizing the strategy may appear mechanical, it is not (given the current state-of-the-art of computer science) an automatable procedure.

The process of identifying the data types, objects, operators, and control structures, even given the English informal strategy, requires a great deal of real-world knowledge and an intuitive understanding of the problem domain.

It is not just a matter of examining the English syntax.»Russel J. Abbott

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The ObjectSage

The ObjectSage is a try to solve Abbott’s problem automatically.

Input: informal textual description.Output: C++ *.h file with class declarations.

The existing prototype has some restrictions described below.

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Current restrictions

Text:– no pronouns– just a few syntactical structures– no modal verbs etc.

Object model:– no variables – types only– no return values for function– almost no simple types

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Demo

Just look at this!It seems to be working!

Launch the demo

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Troubles

• Different meanings of the same word“Time files like arrows” © M. Geipel

• Insufficient information“It’s raining” – whom do you mean?

• Unknown words (specific for problem domain)“A fricosoid could be either cormable or discormable”

• …

Note: there is no need in understanding certain meaning of each word or sentence, in most cases just relative semantics is enough!

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Mathematical model

First an input text is translated into Object Relation Graph(ORG).

It is held using Link Grammar Parser (LGP) developed inthe Carnegie Melon University (USA):

http://www.link.cs.cmu.edu/link/

Using LGP’s output which is a separate link-graph for eachsentence we build ORG subgraphs which could be

connected with pronouns (unsupported now).

Parser G ra p hTe xt

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«There is a shop assistant in the shop.»

Shop assistant

ShopShop assistantTypification

Aggregation orAttribute

Shop object has a shopAssistant attributeof the type ShopAssistant

Type

Belong

Object

Attribute

Legend

Two words are joined intophrase and this phrase gives

out two nodes

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«Pete, shop assistant, sells food.»

Shop assistant Food

Sell

Generalization Parametrization

Pete object has a sell method which takesa Food parameter of the type Food

Type

Belong

Class

Attribute

Legend

Pete

Food

Param Method

ParameterInherit

Formalparameter type

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There are shop assistants in the shop.

They sell things to customers.

There are shop assistants in the shop.

Shop assistants sell things to customers.

Pronoun connection between two sentences

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Principles of operation

ORGraph, produced by the LGP-part is processed by theObjectSage according to the following principle:

ORG vertices with the same names give outan element of the resulting structure.

Objects are joined into classes, attribute-vertices intoattributes and so on.

Finally we get a set of classes called Repository.

G ra p h Ob jectSage

Rep o sito ry

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Objects are joined into classes

Shop assistantSell

Shop assistantLanguage

Shop assistantTalk

Language

Experience

ShopAssistant

experiencelanguage

sell()talk()

New class

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Attribute group gives out an attribute

Language

Shop assistant

European language

Language

Shop assistant

Language

Language

Shop assistant

English

ShopAssistant

experiencelanguage

sell()talk()

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Data manipulationsAll the actions are held using data structures speciallyorganized for that purposes. These are two main ones:

Word dictionary contains all the words used in the original description, each connected with the representing vertex or repository record.

Category structure (thesaurus) organizes all the words into semantically related blocks - categories.

Currently ObjectSage supports only a flat category structure, but it should be organized similar to file system (it should have treelike structure).

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Background knowledge

• Categories (partially supported)Words are coupled by semantics

• Privileges (unsupported)The problem domain might have more and less related areas, that could be described by semantic privileges

• Primitive types (unsupported)Not all the data is represented by classes, there are also simple integers, character and strings

• Existing classes (unsupported)An existing architecture could give some guidelines while adding new classes

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Data scheme

Human

Name

Say

Word

HumanNameSay

Word

Dictionary

Object Relation Graph

Word

datacharset

setAt()getAt()

Human

namelanguage

walk()say()

Categories

Class Repository

Humanity

Personal

Actions

Languages

Source text

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Repository refactoring

Initially we do not get any class hierarchy – just a heap of classes with no connections.

To improve the model quality we use several heuristics, which are mostly aimed to

determining inheritance.

Repository

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SpecifiersOne of the most difficult things held by The ObjectSage isan inheritance recognition. The most reliable method here

is to use specifiers.

A specifier is an attribute which is expressive enoughfor his presence to sign that an object belongs to anew subclass.When a specifier has been found, we decide to createa new subclass, and it is the most reliable heuristicsused by The ObjectSage.

Specifiers are denoted as attributes that occur verystably with a group of objects.

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Class specifiers

GoodsgetCost()

PieceGoodsgetCost()

WeightGoodsgetCost()

For goods sold by piece cost is a multiple of an integerpiece-count and price.

For goods sold by weight cost is a multiple of a fractionalweight, unit coefficient and price.

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Why do we take a whole category as aspecifier?

Weight

Goods

Piece

Goods

Pack

Goods

Categories

Sold by ...

PackGoodsgetCost()

WeightGoodsgetCost()

PieceGoodsgetCost()

Frequentlyused

Rarely used

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Attribute mergingWhen we create subclasses we are to define

their interfaces according to ORGraph.

Attributes pulled up into superclass may havedifferent types, they are to be merged into one

attribute having a superclass type.

When only values of an attribute (not its name)occur in the description, those values are to be

merged into one attribute according to thecategory structure.

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Attribute typification

Language

English

Language

Russian

Language

German

Language

Attribute type cases:1. Full type information (Class)2. Category only3. No type information

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Categories are used as attributes

Green

Car

Red

Car

Blue

Car

Categories

Color

Car

brandcolor

drive()stop()

ColorRED

GREENBLUE

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Method mergingMethods are similar to classes. Arguments

(parameters) are processed as attributes: theyare to be merged, typified etc.

That’s why the methods may have specifiers too.

A method specifier is a parameterwhich is expressive enough for his presence to

sign a new method existence.

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Method specifiers

Do

Human

Dance

Do

Human

Deal

Do

Human

Sum

The same classand method name

Human

doDeal()doSum()

doDance()

Different parameters used frequently

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Dealer

State-of-the-art inheritance hierarchyNote that Food class is not identified as a descendant of

Goods, although semantically it should have been.

GoodsgetCost()

PieceGoodsgetCost()

WeightGoodsgetCost()

Food

ShopAssistant SlotMachine

This problem is solved usingcategories...

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Machines

Humanity

Category-driven inheritance

GoodsgetCost()

PieceGoodsgetCost()

WeightGoodsgetCost()

Food

Categories

Shop

Goods

Food

Category-drivengeneralization

An edge is moved from the category structure tothe repository.

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Food

price

sell()

Pull up method or attribute

Goods

price

sell()

CunsumerGoods

price

sell()

Interface elements with thesame names are pulled up into

the superclass.

A new subclassmight have some

members thatoccurred in his

brother-classes.

These members areto be pulled up into

the superclass.

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C++ Output

LanguageRe p o sito ry

Programclass CClass1 {public: void Method1();private: int Field1;};

The constructed repository is isomorphous to aUML class diagram. So it could be transcribed

into any object-oriented language.

C++ is supported now.

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Usage

• Pre-processing of the requirements.• Incremental architecture building• Increasing an existing architecture

Classes already created by human-developers can give guidelines

to The ObjectSage.

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eXtreme Programming

The ObjectsSage seems to be useful in the XP process:

• User histories could be processed incrementally, using existing architecture

• Each user history is semantically homogeneous – no misunderstanding

• Refactoring allows to improve the architecture quickly

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Thank you for your attention.

Any questions?