Final Exam Review - Spring 2002

Explain the Design Methodology

• What are some ways of getting the development team to understand the customers' problems?
• How do they allow their teams to work separately and yet have easy integration?
• How do they improve the readability of their code?

Designing the Segway Palm

Palm wants some of these features to interoperate. For example:

• The single speaker jack should be internally connectable to either the radio source or the MP3 source. The volume control effects the speaker jack directly, while the band selector effects only the radio source and the clip selector effects only the MP3 source.

• Map objects will be used by the GPS locator (e.g., to tell you where you currently are), by the Zagat's guide (e.g., to show you where the nearest Starbuck's or Waffle House is), and by the address book (e.g., to show you where your Aunt Millie's house is and the quickest way to get there). This means that the map needs to be indexed both by global GPS coordinates and in terms of street addresses, e.g., the maps have to know the GPS coordinates associated with 800 Atlantic Drive. Locations in the address book and in the Zagat's guide can be specified in terms of either GPS coordinates or in terms of street addresses, and the Map objects have to handle translations between them. A single Location will appear on multiple Maps, and if the Location is asked for its coordinatesInGPS or coordinatesOnStreet, it should know one of those and be able to ask any of its Maps for the other. A Map should know how to map any Location to its own graphical representation, such that the Map can highlightFor any Location.

1. (10) Draw a UML class diagram for the interactions between Maps, Locations, the address book, and the Zagat's guide, including any additional objects you think are necessary. You must account for all of the functionality described in this problem, but you needn't add any other (e.g., you don't have to handle the address book user interface). You do need to show attributes and services that would be necessary to implement the given functionality. Describe briefly what each of your services would do.

2. (6) Identify one design pattern that would be useful in this problem. Explain how it would be useful, and identify specific classes that you would use in a design for this problem that would correspond to the design pattern participant objects.

3. (10) Palm is using Squeak to implement the SegPilot. Imagine that you have an ordered collection errands of Location objects that represent places to which you have to run errands. You have a Map gridMap on which all the Locations appear. You are to write workspace code:

   1. To tell gridMap to highlightFor each of these Locations, and

   2. To ask each of the errands locations for its streetname (assume given, returns a string with the name of the street). For each street containing more than one errand location, print to the Transcript a message announcing ``There is more than one errand on street: '' with the street name.

Post comments, discussion, answers at Sp02 Final Exam Review: Segway Palm Pilot.

Programming A Sensor Management System

Helping the Video Game Industry

Given your experience with designing and implementing epic adventure games, you have been hired as a consultant to Electronic Arts as they develop their response to the Myst series of adventure games.

• (5 points) The computer game and video game industry is enormous these days. EA realizes that there are two different potential markets for these games: The 12-18 year old market (low-budget, intense competition with movie industry), and the growing 25-40 year old market (can afford more expensive hardware). EA wants to know if they can have one user interface for both of these markets, or should they think about two user interfaces. How would you help them answer this question? What should they do before they start designing their user interface(s)?
• (5 points) Time passes, and now EA has some storyboards of the game and its interface. They want to know now, before they start coding and without spending too much money, if they're on the right path or have come up with a completely awful interface. What would you recommend they do and why?
• (10 points) EA is considering using a Model-View-Controller (MVC) structure for implementing the user interface for their new game. For example, if the user opens the Arkenchest, all the objects in the room touched by the evil ArkenLord should begin to glow. Trace out for EA the flow of messages in an MVC structure (assuming an object-oriented language, and that all objects in the visible world are View objects) between the user's opening the Arkenchest and the glowing of the objects.
• (5 points) EA used Squeak for their implementation, especially for the multimedia and portability aspects. Now they're looking to optimize some features. For example, parsing the 3-D objects is taking too long. Name at least two things that EA could try in order to speed up their code.

Language Choices

For each of the below applications, you are to pick the object-oriented language of your choice for implementing the application (e.g., Smalltalk in general, Squeak in specific, Java, C++, Eiffel, etc.) and provide your rationale! We don't have a right answer in mind for each of these, but we are looking for true, reasonable statements in your rationale. (E.g., ``I'm going to pick C++ because it gives me the most robust implementation'' would be a bad answer.)

A. You're building a claims-entry system for a large insurance firm. You're not using the Web because you're using your own proprietary secure networking protocol. You have to run on whatever platform the insurance agent may purchase. New claims forms are defined by the company fairly frequently-usually several a month. This requires new GUI forms and new processing code to be implemented for each new form.

B. You're building a new adventure game based on the movie Shrek to run only on Windows boxes with hardware acceleration. You're going to be distributing the code on CD. You'll have a small, hand-picked group of developers who are expert in your language of choice. There is intense pressure to have the game out by summer's end, so you only have a month or two to implement the complete game.

C. The Bell operating companies have decided to finally rewrite TIRKS, the massive multi-million line database system that keeps track of all the phone lines in the country, including keeping track of change records, etc. TIRKS is currently written in PL/1 and System 360 assembler. This rewrite is a huge investment, and it's not expected to be rewritten again for another 30 years-but it must be maintained. It's going to be done in an object-oriented language with a team of hundreds of programmers.

D. You're building an MPEG library for a set-top box. MPEG decoding, of course, is a numeric code that is very compute intensive. The library will be burned into ROM and executed from an embedded ARM processor running only a single application. You expect to sell millions of these boxes, and the library is expected to change very, very little, if at all, after it's finished, since the MPEG spec is cast in stone.

E. You're building a distributed Doom-like game, intended to support players on home PCs and Macs, that tie into a central server over the internet (possibly via a slow link, like a phone line). The game requires heavy, compute-intensive 3D rendering. Players are allowed to define their own characters and weapons; the 3D models and behavioral code for these entities are uploaded to a central server. Instead of running the behavioral code and rendering the models on the central server, they are broadcast to all the other players' computers, where they are executed locally. This allows for crisp interaction over slow communications links-when Felicia fires her laser blaster at George, the laser-gun simulation runs and renders locally on George's computer.

F. You need to choose a language & language implementation to allow people to define the programed behaviors for game characters and weapons-i.e., the bits of code that get shipped around between players.

Cellular Web-browser

You're designing a web crawler for a new cellular-phone service that's going to offer wireless Internet access. The key features that you need your web crawler to provide:

• You have to follow links breadth-first from a list of most-popular sites that marketing is going to provide you, to a depth of 5 clicks from the top.
• As you find these pages, you need to convert them into your company's BCML (Bizarre Cellphone Markup Language), and convert all GIF, JPEG, PNG, and BMP images into the BCI (Bizarre Cellphone Image) format.
• All documents should be stored into the database of the ``cellphone faux HTTP server'' that will serve the appropriate BCML or BCI document for a given URL. This server sits at the phone company, and ships web documents (translated into BCML and BCI format) out to cellphones in response to URL requests.

You begin your design, and you make several decisions about your classes:

• You want a class named CFHserver (Cellphone Faux HTTP server). An instance will handle the store:forURLs: message (defined in detail below), and produce a document when sent the forURL: message. A CFHserver will also know its urlDatabase.
• A class named BCObject will be an abstract superclass, and its concrete subclasses will be BCMLObject and BCIObject. All BCObjects will know how to displayOn: a given Canvas. They will also respond to isBCML and isImage.
• You want the URLdatabase to understand the messages storeDocument:forURL: for BCML documents and storeImage:forURL: for BCI documents. The instances of URLdatabase will know its current file and index.

The CEO is betting the entire company on this new application. Once he discovers you've had CS2340, he instantly promotes you to chief architect of the system. Here are your immediate tasks:

(15 points) Draw a class diagram for the classes CFHserver, BCObject, BCMLObject, BCIObject, and URLdatabase.

(10 points) Identify at least one other UML diagram (your choice which one!) that would be useful in describing how this design would work. Describe the UML diagram you have chosen, why you have chosen it, and what it would show that the class diagram does not.

(10 points) Imagine that you are now actually implementing this design. Your CFHserver will be sent the message store:forURLs: which will take two arguments: An ordered collection of BCMLObject and BCIObject objects, and a matching ordered collection of Strings containing the URLs for the HTML/GIF/whatever matching documents. You want to store these into the database of the server. You may use any of the methods described above.

Write the Squeak method store:forURLs: for CFHserver.

Virtual Machines

• Give three reasons that one might use a virtual machine (and compiling to native code) instead of a compiler to compile directly to machine code.
• Give three good and frequent reasons that one might add a primitive to a VM.
• What takes up the majority of time and effort in a VM (typically)?
• Why are VMs so often stack-based architectures? Why not have registers?

Optimization: Collection Differences

The Issues of Serialization

• Identify three challenges to the strategy adopted by Microsoft in their .NET Framework where objects will be serialized to XML and XML instances (defined through XML Schemas) can be compiled to objects.

• What are XML schemas? How are they like and unlike class definitions?

• What's the argument that XML "instances" aren't really objects?

eXtreme Programming

1. "XP programmers don't document their code!?! How can their code still be readable after they write it?"

1. "What in the world do they mean that code written by an individual has to be thrown away? What other kind of code is there?"

1. "Integrating daily sounds like we'll spend all our time in integration. How can we make daily integration work more smoothly?"

1. "Is there any evidence that this really works?"

Re-designing a Networked Computer Game

Tools for Space Scientists

• Data Collection Documents: Containing live satellite data in a form appropriate for doing numeric calculations with.

• Data Visualization Documents: Does 2-D and 3-D graphs of satellite data linked to it.

• Data Planning Documents: For organizing modules both on the satellite and off for gathering and processing sensor data.

Designing Networked Games

Transposing a Dictionary

MVC vs. Morphic

HCI Design

Tradeoffs

Design Patterns

Multimedia Programming in Squeak

(AbstractSound noteSequenceOn:
    (FMSound soundNamed: 'brass1')
    from: #((c4 1.0 500) (d4 1.0 500) (e4 1.0 5000))) play
    "Triplet are note, duration, and volume"

Whiz-O Toys

• "We usually have multiple teams of developers working on different parts of the programs at once. How does object-orientation help us with that?"
  
  
• "We rely heavily on simulation when developing sophisticated toys. What would be absolutely perfect would be if we could take parts of our simulation and use it in the code for the real toy. Can we do that? How?"
  
  
• "What happens if we develop add-ons for a toy, like a new Laser Gun for our Omega Video Game System? Or if we develop a new variation on a toy, like the Phaser Range Finder Gun (which is like the Laser Gun)? Can O-O help our productivity in doing this?"
  

Design an Alarm System

• For any kind of alarm, you need to send all the alerts necessary for a given alarm. For example, for all fire alarms, the fire department is always called. The head of the house or business is always called for all alarm, and one or more "local experts" might also be called. For example, if there is a fire or intruder in the warehouse, the warehouse manager should also be called.
  
  
• You need to respond to Intruders by sounding the audio alarm in the vicinity. Assume that you just send the message trigger to the audio alarm object and it will sound.
  
  
• You need to respond to Fire by triggering the sprinklers in the vicinity, if available. Assume that you just send the message trigger to the sprinklers object.
  
  
• Your system is pretty sophisticated with respect to alerting authorities. It can handle IP or phone messaging. You can assume that the messaging is handled by another piece of the system. You need to provide the address of the authority (i.e., either a phone number or an email address) and the message to be sent (which should include, for example, the kind of alarm and the alarm vicinity).
  
  

• What classes do you need? What service do each need to provide? What attributes do each need to know?
  
  
• Where are there generalization-specialization relationships? Where are there part-whole relationships?
  
  

Note! This is an important one!

Links to this Page

• Reviews last edited on 24 July 2007 at 2:44 pm by balladeer.cc.gatech.edu
• Spring 2002 Announcements last edited on 19 July 2005 at 12:36 pm by c-24-98-52-85.hsd1.ga.comcast.net