CompSci 308
Spring 2024
Advanced Software Design and Implementation

Lab Team Meeting: Preparing for SLogo

In this lab, you will practice designing APIs, the public classes and their public methods. Thinking about public methods as a service has the power to change your purpose: from simply programming to finish functionality to providing a means to help other programmers innovate (even those on your own team!). An API then, is essentially a contract with developers, now clients, who are enticed to use the API because they know they can rely on the stability of that contract (even if the underlying implementation changes). Thus, many see API design as the most critical part of designing a program, because it affects the design of other dependent components.

In your SLogo teams, complete the following steps:

  1. Introduce yourselves by sharing:
    • your background and how you are doing in general this semester
    • your motivation/interest in this course
    • your knowledge/interest in other programming languages (especially Logo, Alice, Scratch, Lisp, or something similar) and APIs
    • areas of the project you interested/concerned about
  2. Discuss each person's team experiences and expectations:
    • share good and bad past team experiences and what you learned from them
    • share preferences and styles regarding expectations, communication, and debating/conflict
    • go over the Team Contract (which you will submit individually)
    • choose a time for the next team meeting
  3. Practice thinking critically about API design
  4. Practice designing APIs
  5. Project API design
  6. Plan your project

For shared Markdown editing, you can work

The result of this lab will be a set of documents that captures the important points of your team's several directed discussions.

Practice Thinking Critically about API Design

Complete this exercise to examine Java's Collections API from a design perspective (instead of as a user) to compare your experiences with its documented goals and motivations.

Before Moving On: Add your names and summary of your critical discussion to the file doc/, then add, commit the file, and push it to your shared slogo_teamNN repository.

Practice Designing APIs: Cell Society

In many projects, APIs serve two different goals based on the clients (other programmers): consumers that use the API and providers that implement/maintain the API:

Examine one person's Cell Society project the perspective of APIs by categorizing each public or protected method in the Model as:

A simplified view of only the public/protected methods for each team is available here.

Now that you have a sense of the kind of service your project actually provides to programmers, think about the kind of service you wish it provided. In other words, spend this time designing the API instead of just having it happen. Write a simplified (i.e., less than "one page" each) description and goals of both the internal and external Model API. Note which classes are abstract/interface and which concrete and, for concrete classes that are part of the external API, justify why they do not need to represent an abstraction.

Then describe how to use your new external and internal APIs to do the following tasks:

Your written explanation should include both English and Java descriptions of the task:

Before Moving On: Add the following to the file doc/, and add, commit the file, and push it to your shared slogo_teamNN repository:

Project API Design: SLogo

Discuss high level design ideas and possible APIs for the SLogo project without worrying about the implementation details (a specific data structure, the parsing algorithm, or the exact layout and OpenJFX components needed). Also discuss any issues or concerns anyone has about the project's specifications or goals.

Consider the following questions:

Write a simplified description for the Model's External and Internal APIs (i.e., no more than "one page" each) that incorporates your vision for each as well as the classes and methods. Note which classes you expect to be abstractions (e.g., abstract or interface) and which concrete. For the concrete classes, justify why they do not need to be an abstraction. A class's behavior is its public methods, including any parameters and a return value. These method signatures can be written as they would appear in Java code, but your focus should be on describing their purpose in the class, not their implementation. To summarize a class and its purpose, highlight only the most important methods in this first draft.

Ideally, without any coding or requiring any specific implementation, try to explore trade-offs between several designs and to determine the best one to explore in detail (creating simplified UML style pictures can be helpful here using Markdown).

Class-Responsibility-Collaborator Cards

Now that your team has thought about the problem generally, use CRC cards to refine your design and help you focus on interface instead of implementation issues. A CRC card help show the objects more conceptually and the logical relationship between objects more explicitly, making it is easier to understand, evaluate, and modify a design. Answering the following questions about each class helps see them as smart/anthropomorphic collaborators:

Here are some examples of completed CRC cards. In these examples, the actions are given in English, not as a Java method signature (name, parameters, and return type). Your version must be written as a Java signature to provide more details about the flow of the program.

Use Cases

The following scenarios are provided to help test the completeness of your design. By writing the steps needed to complete each case below you will be able to see how effectively your design handles these scenarios and others will be able to better understand how deeply you have considered the basic issues. It may help to role play or draw a diagram of how your classes collaborate to complete each case. For this exercise each step, try to include both the class used and the method used to accomplish the step.

Here are some examples of completed Use Cases. In these examples, the steps are given in English, not as a Java method calls. Your version should be written as a sequence of calls to only those Java methods on your CRC cards to provide more details about the flow of the program.

To make things more interesting, pair up with another team and try to do this part using their CRC cards!

Submitting your Work

At the end of lab, push your team's Markdown files to the doc folder of your provided, shared, slogo_teamNN repository to submit your notes about your teams' discussions.

Make sure the text of your final commit message is of the form "lab_slogo_design - NetIDs".