Formal Specification of Non-Functional Aspects

in Two-Level Grammar

Chunmin Yang, Beum-Seuk Lee, Barrett Bryant, Carol Burt

University of Alabama at Birmingham

Rajeev Raje Indiana University Purdue University Indianapolis

Mikhail Auguston Andrew OlsonNew Mexico State University

This research is based upon work supported by, or in part by, the U. S. Army Research Laboratory and the U.S. Army Research Office under contract/grant number DAAD19-00-1-0350 and by the U. S. Office of Naval Research under award number N00014-01-1-0746.

Contents

Problem Statement

System Structure

Two-Level Grammar (TLG)

Case Study – ATM Example

Conclusion

Objectives

Motivation

Approach

Natural Language Processing

Knowledge Base

Non-Functional Aspect (QoS)

2

Problem Statement

3

Functional aspect Non-functional aspect

Well defined domain (concrete) Abstract and non-quantifiable

Local and simple attributes correlation

Dynamic and complex correlation

Easy prototyping and verification Poor measurement and formalism

Users’ main interest Its importance neglected

“the system should sort the list of the given numbers”

“the system should maintain high level of security”

Non-functional aspect (Quality of Service - QoS) in the UniFrame project

Query of heterogeneous components that satisfy certain QoSQoS specification and management

Objectives

Formal specification of QoS

Decomposability of QoS attributes

4

Correlation among QoS actions

QoS specifications in natural language

User friendly interface

Reuse of requirements document

Two-level Grammar (TLG)

Natural Language Processing (NLP)

System Structure

Know ledge Base

T wo Level Grammar

Vienna Development M ethod

J ava, C++

I FAD VDM T ool K it

Q oS Requirements Document in XM L

UM L

Code generators

Rose-VDM Link

N atural Language Processing

Decontextualization

Data and Function translation

I nformal

Formal

Q oS Requirements Document in N L

I n terpreter

5

Non-functional Aspect (QoS)

QoS attributes

Features or parameters of QoS

6

QoS catalog : throughput, capacity, end-to-end delay, parallelism constraints, availability, ordering constraints, error rate, security, transmission, adaptivity, evolvability, reliability, stability, result, achievability, priority, compatibility, and presentation

QoS actions

Events that have affect on QoS attributes

Correlation

Decomposition

QoS propertiesConstraints on QoS actions

Natural Language Processing

Syn

tax

Leve

lPart of Speech Parsing

Part of Sentence Parsing

QoS D escription

Se

ma

ntics

Leve

lPronouns

Pra

gm

atics

Leve

lContext

Know ledge Base

7

Natural Language Processing (Cont’d)

Sentence

Noun_ Phrase Verb_ Phrase

Pronoun Verb Propos_ Phrase

Proposition

tim e flies like

Subject Verb Proposition Modifi er Prop_ Object

Noun_ Phrase

Article Noun

an arrow

8

Knowledge Base

Tree-like structure

Composed of

Linguistics information – parts of speech

Contextual information – relations between sentences

Example

9

A TM Security

update level

be 6Encrypt io n byt e length

M aximum allo w ed at t empt s be less than 5

update attributes

be 80% secureSystem

be a savings accountA ccount type

M aximum co nnect io ns o f bank be less than 50

be lim ited to 4Maxim um allow ed attem pts

Delay level be less than 50

Syntax

Properties

Natural-language-like syntax Flexibility

Formal notation Formalism

Object-oriented structure Abstraction

Logic/Functional operation Computation

Two-Level Grammar (TLG)

class Class_Name. Data_Name {, Data_Name} :: Data_Type {, Data_Type}. Rule_Name : Rule_Body {, Rule_Body} {; Rule_Body}. end class.

10

Two-Level Grammar - Example

class Palindrome.

Char :: Character. Str :: {Char}*.

Empty is a palindrome. Char is a palindrome. Char Str Char is a palindrome : Str is a palindrome.

end class.

11

ATM – QoS Requirements Document in NL

ATM's security property is as follows.

The length of the encryption byte should be bigger than 3 and the allowed attempts has to be smaller than the maximum allowed attempts.

If the encryption byte length is 6 and the maximum allowed attempts is less than 5 then the system is 80% secure.

If the account type is a savings account or the maximum allowed connections of the bank is less than 50 or the delay level is less than 50 then the maximum allowed attempts is limited to 4.

If the user timeout is between 10000 and 120000 milliseconds we have a good delay level.

If the response time is longer than 30000 milliseconds, the delay level drops down to 40%.

12

ATM – QoS Requirements in XML

<c title = "ATM"> <c title = "Security"> <p meta = "satisfaction check"> <s>The length of the encryption byte should be bigger than 3 and the allowed attempts has to be smaller than the maximum allowed attempts</s> </p> <p meta = "level update"> <s>If the encryption byte length is 6 and the allowed attempts is less than 5 then the system is 80% secure</s> </p> <p meta = "attribute update"> <s>If the account type is a savings account or the maximum allowed connections of the bank is less than 50 or the delay level is less than 50 then the maximum allowed attempts is limited to 4</s> </p> </c> <c title = "Delay"> <p meta = "satisfaction check"> <s>If the user timeout is between 10000 and 120000 milliseconds we have a good delay level</s> </p> <p meta = "level update"> <s>If the response time is longer than 30000 milliseconds the delay level drops down to 40%</s> </p> </c></c>

13

ATM - Knowledge Base

14

A T M

Security

Delay

sat isfact io n check

update level

be b igger than 3Lengt h o f encrypt io n byt e

be sm aller thanA llow ed attem pts

be 6Encrypt io n byt e lengt h

M aximum allo w ed at t empt s be less than 5

updat e at t ribut es

Maxim um allow ed attem pts

be 80% secureSystem

be a savings accountA ccount type

M aximum co nnect io ns o f bank be less than 50

be lim ited to 4Maxim um allow ed attem pts

Delay level be less than 50

sat isfact io n check

update levelbe longer than 30000 m illisecondsR esponse tim e

dro p do w n t o 4 0 %Delay level

be betw een 10000 and 120000 m illisecondsUser tim eout

have Good delay level

ATM – Two-Level Grammar (TLG)

class Property. Level :: int.end class.

class Bank_Capacity extends Property. Maximum_Connections :: Integer.end class.

class ATM_Delay extends Property.

Response_Time :: Integer. User_Timeout :: Integer.

check satisfaction : User_Timeout > 10000, User_Timeout < 120000.

update level : Response_Time > 30000, Level := 40.

end class.

15

ATM – Two-Level Grammar (cont’d)

class ATM_Security extends Property.

Maximum_Allowed_Attempts :: Integer. Encryption_Byte_Length :: Integer. Allowed_Attempts :: Integer. Account_Type :: String.

check satisfaction : Encryption_Byte_Length > 3, Allowed_Attempts < Maximum_Allowed_Attempts.

update level : Encryption_Byte_Length = 6, Allowed_Attempts < 5, Level := 80.

update attributes : Account_Type = "savings", Maximum_Allowed_Attempts := 4; Bank_Capacity Maximum_Connections < 50, Maximum_Allowed_Attempts := 4; ATM_Delay Level < 50, Maximum_Allowed_Attempts := 4.

end class. 16

ATM - Unified Modeling Language (UML)

17

Conclusion

18

Summary

Formal specification of QoS using TLG

QoS specifications in natural language using NLP

Express the constraints in Object Constraint Language (OCL)

Future Work

Combine Model Driven Architecture (MDA) and formal methods in representing the QoS properties, and implement the representation within MDA

THE END

Beum-Seuk Lee : leebs@cis.uab.edu

www.cis.uab.edu/info/grads/leebs

UniFrame : www.cs.iupui.edu/uniFrame

Contact info :