代写program、代做Java编程语言

日期：2024-04-14 10:58

Objective

To use a higher-level modelling language to specify and reason about a concurrent system.

Background and context

Assignment 1 has two parts. The first part, 1a, was worth 12.5% of your final mark; this

part, 1b, is worth 12.5%. In the first part (which you should complete before attempting this

part) you designed and implemented (in Java) a concurrent simulation of a hospital emergency

department. Now your task is to model that system using FSP, to use LTSA to check your

model, and to identify and mitigate any problems that you discover through modelling.

The tasks

1. Model: The first task is to model your implementation from Assignment 1a in FSP. That

is, reverse engineer an FSP model from your Java implementation. Your model should

contain comments that explain the design and its components. NB: If your implementation

in Assignment 1a was incomplete, or too incorrect to form the basis of an FSP model, you

may wish to construct your model based on the system description in the Assignment 1a

specification.

2. Check: Specify what you believe are the relevant safety and liveness properties for your

FSP model. Note: for liveness, it may be the case that only a small number of properties

are required. Use LTSA to check these properties.

3. Modify: You will most likely have discovered, either while completing Assignment 1a, or

while completing Tasks 1 and 2 of this Assignment, that there is a potential issue with the

operation of the system.)

Propose at least one modification to the design of the system that mitigates this problem

and update your FSP model. If you wish, you may also implement this modification in

your original Java implementation of the system, and satisfy yourself that it now behaves

“correctly” (ie, does not violate safety or liveness properties). Note: You do not need to

re-submit your Java code!

Be sure to create a copy of the file containing your original FSP model. You are required

to submit both the original model from Task 1, and the modified model from Task 3 as

separate files.

4. Discuss: Discuss your original and modified models. Points you may wish to address

include:

? What (if any) problems did you find in your original model as a result of using LTSA?

? Had you identified these in your Java implementation?

? If not, why do you think you picked these up now and not before submitting Assignment 1a?

? What was the reasoning behind the changes you suggested in your modified model?

Are there any trade-offs in system performance associated with your suggestion?

? If you did not find problems with your original implementation, were you convinced

when you submitted Assignment 1a that no problems existed? Why did you believe

this? Do you still believe there are no problems?

Keep your discussion to no more than 500 words

Procedure and assessment

The assignment should be completed by students individually. A late submission will attract a

penalty of 1 mark for every calendar day it is late. If you have a reason that you require an

extension, email Nic well before the due date to discuss this.

To tackle the assignment, first work through (and understand) the examples from lectures,

and do the workshop exercises. FSP is not difficult—it is simpler than most programming

languages, and much simpler than languages like Java. However, as with other languages, the

way to master it is to use it, and to learn by doing. Trying to do the assignment straight up

means you may struggle. Work through some easier examples first.

Submit a single zip file via the LMS. The file should include

? A file called model.lts with your initial FSP model, including the safety and liveness

properties from Task 2.

? A file called model_modified.lts with your modified/corrected model, including the

safety and liveness properties from Task 2.

? A plain text file called discussion.txt, containing the discussion of issues. Please ensure

that this is a plain text file; ie, not a doc, docx, rtf, or other file type that requires specific

software to read.

All model files and your discussion file should contain, near the top of the file, your name

and student number.

We encourage the use of the subject discussion board for discussions about the project.

However, all submitted work is to be your own individual work.

This project counts for 15 of the 50 marks allocated to project work in this subject. Marks

will be awarded according to the following guidelines:

Criterion Description Marks

Clarity & Abstraction FSP models are at a suitable level of abstraction. All behaviours relevant to interaction are specified, and there is

sufficient detail to implement the system from the model.

3 marks

Completeness The model is complete. All components have been modelled

and all expected behaviour is present. Suitable safety and

liveness properties have been described.

3 marks

Correctness The original FSP model accurately reflects the original Java

implementation (or specification). The modified FSP model

behaves is free of any problems identified in the original

model, does not violate any safety properties, and demonstrates all liveness properties.

3 marks

Formatting The FSP source adheres to the code format rules from Assignment 1a where this makes sense, including the use of

comments to document model components and properties.

2 marks

Discussion The discussion shows understanding of the subject material. 1.5 marks

Total 15 marks

Why backwards?

A valid question: Why are we modelling the system after implementing it? Should it not be

done the other way? Well, yes and no. Many people use modelling to understand an existing

code base (just look at the number of tools for reverse engineering UML models from code

bases). Reverse engineering is a great way to understand problems with an existing system. It

is true, however, that in many cases, it would be cheaper and easier to do the modelling first.

The other reason why the assignment is “backwards” is that trying to model a new system

using a new type of notation, such as FSP, will often end in disaster. We hope that, having gone

through the Java programming stage, you feel familiar with the system to be modelled and thus

can concentrate on the use of FSP. The exercise should be one of applying abstraction—a skill

that is of utmost importance in any engineering discipline.