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Building a simple social server using java and maude

October 28, 2015 0 Comment

Assignment Requirements

this assignment consists of many tasks that includes the use of maude programming language as well as java.

link: http://cgi.csc.liv.ac.uk/~grant/Teaching/COMP213/Assignments/FriendFace/Ass1/index.html

Background: The FriendFace Server

FriendFace is intended to be a social networking application for people who are more interested in networking than socialising. Users of this application can do the following.

Register to become a member of FriendFace. In order to register, a user need only supply the name by which they wish to be known. We shall assume that this name is a string that doesn’t contain a newline, but you don’t need to check for this condition. Henceforth, we’ll refer to a registered user as a “Member”. Names should be unique: if a user attempts to register with a name that has already been taken by an existing Member, then the attempt will be ignored.
Request to become friend to another Member. Each Member has a list of friends. All of these friends are Members (i.e., registered users). A friend-request is therefore determined by two strings: the name of the Member requesting the friendship, and the name of the Member they want to be friends with. If one or both of these strings turns out not to be the name of a Member, then the request is ignored.
Get a list of all friend requests for a particular Member. Given the name of a member, this should return a string containing the names of all members who have requested to become friends with that member, where each name occurs on a separate line. For example, if Roy and Jen have requested to become friends with Moss, then getting the friend requests for “Moss” should return the string “RoynJenn” (the order in which the names occur is not important).
Reject a friend request. The request will be removed from the system, in that it will not appear in any further list of friend requests.
Accept a friend request for a given member. The request will be removed, and the requester will be added to the list of friends of the member; the member will also be added to the list of friends of the requester.
Get the friends of a given Member’s friends. This should return a string with all the friends-of-friends’ names on separate lines. For example, if Jen and Roy are friends of Moss, and Roy is a friend of Jen, and Delina is a friend of Jen, then the getting the friends-of-friends for Moss should return the string “RoynJennDelinan” (again, the order in which the names occur is not important).
This basic functionality is partially specified in the Maude module FRIENDFACE in the file friendFace.maude, which specifies the sort FriendFace and six operations, register, addRequest, getRequests, acceptRequest, refuseRequest, getFFriends and which give the functionality described above. All of the other sorts and operations in the module are “helper” sorts and operations; they are only there to help us specify the functionality of our six main operations.

Task 1: complete the Maude specification

The module includes equations that define all the operations except acceptRequest; you should complete the specification by adding equations to define the functionality of this operation: this may involve adding some helper operations (one helper operation, remove, is declared but needs equations to define it: you should add these equations). In addition, the operations addRequest and getRequests have helper operations isIn and getReqs that are missing equations: you should add equations to complete the specification of the functionality. Add your equations and helper operations to the file friendFace.maude and submit this completed specification.

Task 2: test the Maude specification

The file friendFaceTest.maude contains some test reductions. These only test the functionality of register, getRequests, and getFFriends; you should add more test reductions that test all of the six main operations. These test reductions will give a test of your solution to Task 1. Add your tests to the file friendFaceTest.maude and submit your edited file.

Task 3: implement the FriendFace functionality in Java

To implement this in Java, you need to implement a class FriendFace with six public operations. A skeleton of such an implementation is given in the file FriendFace.java. Your implementation should use various lists (e.g., of members, requests, etc.), you should implement these yourself as linked lists (possibly generic): do not use, for example, arrays or java.util.LinkedList.

Note that you need to implement the functionality of the six operations register, addRequest, getRequests, acceptRequest, refuseRequest, getFFriends; you do not need to implement any of the helper sorts or operations. Some of the helper operations, such as isIn will be useful, but others will not be useful. For example, you can implement getFFriends with a simple nested loop, which will give a much more elegant solution than implementing helper methods getAllFriends, etc. Similarly, if you implement a class Member, it would make sense to store their list of friends as a list of Members rather than a list of strings as in the Maude spec.

It is also possible to change the types of some of the operations in the Maude spec. For example,

op register : String FriendFace -> FriendFace .
could be implemented as
public void register(String name) { … }
but in FriendFace.java it has a boolean return type, which will be useful in Assignment 2 when you implement the FriendFace server: if a user tries to register with an existing name, register will return false and the client can be informed that the name is already taken.
Similarly, if you choose to implement a helper method isIn you could make its return type the same type as type of the elements in the list, returning null if there is no element in the list with the parameter string as name, and returning the found object itself if there is such an element. Such a method might be used as follows

SomeType result = myList.isIn(“Moss”);
if (result == null) {
// no object called “Moss” in myList

} else {
// found object named “Moss”, do something with result

Apart from the requirement that you use linked lists, you are free to implement FriendFace in any way that meets the given specification.
Task 4: test your Java implementation

Class FriendFace in FriendFace.java has a main method with tests corresponding to the three test reductions in friendFace.maude. You are asked to add more Maude test reductions, and you should add corresponding tests to the main method in class FriendFace. These tests should give the same results as the test reductions you add to friendFace.maude.

Task 5: document your Java implementation

Each class, method, field and constructor in your Java implementation should have a javadoc comment, even if its scope is private. You should use @param and @return tags where appropriate.


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