Question

Ben Bitdiddle has missed one meeting too many. Fearing that his habit of forgetting meetings could cost him his job, Ben decides to do something about it. He adds all the weekly meetings of the firm to the Microshaft data base by asserting the following: (meeting accounting (Monday 9am)) (meeting administration (Monday 10am)) (meeting computer (Wednesday 3pm)) (meeting administration (Friday 1pm)) Each of the above assertions is for a meeting of an entire division. Ben also adds an entry for the company-wide meeting that spans all the divisions. All of the company's employees attend this meeting. (meeting whole-company (Wednesday \(4 \mathrm{pm}\) )) a. On Friday morning, Ben wants to query the data base for all the meetings that occur that day. What query should he use? b. Alyssa P. Hacker is unimpressed. She thinks it would be much more useful to be able to ask for her meetings by specif ying her name. So she designs a rule that says that a person's meetings include all whole-company meetings plus all meetings of that person's division. Fill in the body of Alyssa's rule. (rule (meeting-time ?person ?day-and-time) \(\langle\) rule-body \(\rangle\) ) c. Alyssa arrives at work on Wednesday morning and wonders what meetings she has to attend that day. Having defined the above rule, what query should she make to find this out?

Short answer

a. Query: `(meeting ?division (Friday ?time))`. b. Rule: `(or (meeting whole-company ?day-and-time) (meeting ?person-division ?day-and-time))`. c. Query: `(meeting-time Alyssa (Wednesday ?time))`.

Step-by-step solution

Understanding the Database Queries

We start by interpreting Ben's data. Ben uses a database to store information about meetings. Each entry has a meeting type (division-specific or whole-company), a division name, and a day-time object representing when the meeting occurs. Our task is to create queries to retrieve this information.

Query for Friday Meetings

For part a, Ben needs to query for all meetings happening on Friday. The database uses the format \( (meeting \; \text{division-name} \; (day \; time)) \). Thus, the query must specify the day as Friday without providing a division name or time to implicitly "match all". The correct query is `(meeting ?division (Friday ?time))`.

Design Alyssa's Rule

For part b, Alyssa needs to write a rule that matches meetings where a person must attend. This includes the whole-company meetings and the meetings of the person's division. A possible rule body would unify for a person's meeting times by querying `(meeting whole-company ?day-and-time)` AND `(meeting division-name ?person-division ?day-and-time)`. The full rule body looks like this: `(or (meeting whole-company ?day-and-time) (meeting ?person-division ?day-and-time))`.

Query Alyssa's Wednesday Meetings

For part c, Alyssa wants to know her meetings on Wednesday. The query will use her rule, targeting specifically Wednesday. Assuming her division is known and named `alyssa-division`, the query would be `(meeting-time Alyssa (Wednesday ?time))` which retrieves all `?time` values on Wednesday for Alyssa's meetings.

Key concepts

Query Formulation

Query formulation is about creating the right commands to extract the necessary data from a database. Ben Bitdiddle needs to find all meetings on a specific day, like Friday. By accurately forming his query without specifying divisions or time, he can retrieve all meetings on that day. The syntax `(meeting ?division (Friday ?time))` is used. Here, `?division` and `?time` act as variables, representing any division and any time, respectively. This method allows for broad data retrieval based on simpler criteria, which is essential when specific details are not needed initially. Crafting queries using placeholders enables us to form questions that can adjust to different facets of the stored information. This flexibility helps in exploring various data patterns without modifying the core data each time.

Logic Programming

Logic programming is a style of programming where you define rules and relationships. Alyssa wants to identify meetings she must attend using her name instead of division names. Her approach involves creating a rule that captures a mix of personal and company-wide meetings. The rule for this is `(or (meeting whole-company ?day-and-time) (meeting division-name ?person-division ?day-and-time))`. Using `or` logic here is crucial, as it allows for multiple scenarios:

• A person attends a whole-company meeting, or
• A person attends their division's meeting.

This logical setup means the program doesn't rely on just one factor to provide results. Instead, it encompasses a broader scope, aiding in querying complex data.

Data Definition

Data definition involves specifying what kind of information the database holds. In Ben Bitdiddle's context, each entry represents a meeting with fields such as division/type, day, and time. Defining data this way enables database queries to be both specific and flexible. Having a consistent format, like `(meeting division (day time))`, ensures that all queries can be standard and predictable. By using this consistent definition, you streamline the query formulation process and maintain robust and error-free database entries. Additionally, structured data definition makes updating or adding data simple and consistent, reducing the chances of data mishaps.

Information Retrieval

Information retrieval is a process of obtaining relevant data from a database based on a defined query. For Alyssa, retrieving her meeting schedule on Wednesday involves using the rule she defined, combined with a specific day focus. The query `(meeting-time Alyssa (Wednesday ?time))` demonstrates this. Here, `?time` is a variable representing different meeting times available for Alyssa on Wednesday. By effectively defining and using queries, Alyssa can dynamically access her meeting data without sorting through irrelevant information manually. This approach streamlines data access, making it efficient and user-friendly, an invaluable asset for managing data within large systems.