Lecture Formal methods in software engineering - Lecture 30 - TRƯỜNG CÁN BỘ QUẢN LÝ GIÁO DỤC THÀNH PHỐ HỒ CHÍ MINH

AsmL can be used to faithfully capture the abstract structure and step-wise behaviour of any discrete systems, including very complex ones such as:.. Integrated circuits, software co[r]

Formal Methods in SE

Lecture 30

OSI reference model

Application

Presentation

Session

Transport

Network

Data link

Physical

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Communica tions medium

Network Data link Physical

Application Presentation Session

Transport Network Data link Physical

Application

Model-based specification

Algebraic specification

Language (AsmL)

AsmL is a language for modelling the structure

and behaviour of digital systems

AsmL can be used to faithfully capture the

abstract structure and step-wise behaviour of

any discrete systems, including very complex

ones such as:

both hardware and software

Abstract State

An AsmL model is said to be abstract because it

encodes only those aspects of the system’s structure that affect the behaviour being modelled

The goal is to use the minimum amount of detail

that accurately reproduces (or predicts) the

behaviour of the system

Abstraction helps us reduce complex problems into

manageable units and prevents us from getting lost in a sea of details

AsmL provides a variety of features that allow you to describe the 

relevant state of a system in a very economical, high­level way 

Turing Machine

An abstract state machine is a particular

kind of mathematical machine, like the

Turing machine (TM)

But unlike a TM, ASMs may be defined a

very high level of abstraction

An easy way to understand ASMs is to see

them as defining a succession of states

that may follow an initial state

State transitions

The behaviour of a machine (its run) can always

be depicted as a sequence of states linked by

state transitions

• Moving from state A to state B is a  state 

transition

paint in green paint in red

Each state is a particular “configuration” of the machine

The state may be simple or it may be very

large, with complex structure

But no matter how complex the state might

be, each step of the machine’s operation can

be seen as a well-defined transition from

one particular state to another

Evolution of state variables

paint in green paint in red

We can view any machine’s state as a dictionary of

(Name, Value)

pairs, called state variables

(Colour, Red) is a variable, where  “Colour”  is  the name of variable,  “Red”  is the value

Evolution of state variables

Names are given by the machine’s symbolic vocabulary

Values are fixed elements, like numbers and strings of characters

The  run of a machine  is a  series of

 results form applying operations

 to each state in succession

Diagram shows the run of a machine that models how orders might be processed

S1

S3

S2

Each transition operation:  

• can be seen as the result of invoking the  machine’s 

• calculates the subsequence state as output