Question

Insatiable Enterprises, Inc., is a highly decentralized conglomerate company consisting of a large number of independent divisions located all over the world. The company's computer facilities have just been interconnected by means of a clever network-interfacing scheme that makes the entire network appear to any user to be a single computer. Insatiable's president, in her first attempt to exploit the ability of the network to extract administrative information from division files, is dismayed to discover that, although all the division files have been implemented as data structures in Scheme, the particular data structure used varies from division to division. A meeting of division managers is hastily called to search for a strategy to integrate the files that will satisfy headquarters' needs while preserving the existing autonomy of the divisions. Show how such a strategy can be implemented with data-directed programming. As an example, suppose that each division's personnel records consist of a single file, which contains a set of records keyed on employees' names. The structure of the set varies from division to division. Furthermore, each employee's record is itself a set (structured differently from division to division) that contains information keyed under identifiers such as address and salary. In particular: a. Implement for headquarters a get-record procedure that retrieves a specified employee's record from a specified personnel file. The procedure should be applicable to any division's file. Explain how the individual divisions' files should be structured. In particular, what type information must be supplied? b. Implement for headquarters a get-salary procedure that returns the salary information from a given employee's record from any division's personnel file. How should the record be structured in order to make this operation work? c. Implement for headquarters a find-employee-record procedure. This should search all the divisions' files for the record of a given employee and return the record. Assume that this procedure takes as arguments an employee's name and a list of all the divisions' files. d. When Insatiable takes over a new company, what changes must be made in order to incorporate the new personnel information into the central system?

Short answer

Use a central dispatch table system to map division identifiers to functions for data access, enabling easy retrieval and updates when new divisions join.

Step-by-step solution

Understand Data-Directed Programming

Data-directed programming is a design pattern used to handle multiple data representations without including the conditional logic that handles different cases explicitly everywhere. Instead, it uses a data structure to map types to procedures that handle these types.

Structure for the Personnel File (a)

Create a uniform structure across divisive files by having a dispatch table that maps division identifiers to corresponding data access procedures. The files are accessed via these procedures, abstracting away differences in actual data structures.

Implementing get-record Procedure

Define a global table mapping each division's identifier to a record retrieval procedure for that division. The `get-record` function looks up a division in the table to call the appropriate retrieval function for the specified employee's record.

Structuring the Employee Record (b)

Within a division's file, each employee's record also follows a type-dispatch architecture with key-type identifiers mapping to access procedures for fields like 'salary' or 'address' in records.

Implementing get-salary Procedure

Similar to `get-record`, the `get-salary` function consults a dispatch table keyed on the record type to retrieve the procedure for accessing salary information. It then calls this procedure using the employee's record.

Implementing find-employee-record Procedure (c)

Loop over all divisions' files or use functional mapping to call `get-record` on each division. Combine the results to check which division contains the record, returning the complete employee information.

Adding New Divisions to the System (d)

Incorporate new divisions by registering their data access procedures in the central dispatch tables. This involves adding an entry for their file retrieval and record field access procedures, ensuring compatibility with the existing framework.

Key concepts

Decentralized Organizations

Decentralized organizations, like Insatiable Enterprises, Inc., distribute decision-making powers across various divisions. Each division operates independently but collaborates towards common company goals, leveraging the interconnectedness of their computer systems. This kind of structure enhances flexibility and empowers division managers to make decisions swiftly.

In the context of the problem, each division's autonomy in handling personnel records creates challenges when trying to integrate and retrieve information across a decentralized network. The widespread independence can sometimes lead to inconsistencies, as divisions might adopt different data structures or systems. However, the network ensures that all divisions are linked digitally, making it appear as a single, cohesive unit to users. Thus, although decentralized, they need a strategy for standardizing information retrieval.

Data-directed programming offers an exemplary approach to managing decentralized systems by mapping various data formats to consistent access procedures. It maintains division autonomy while standardizing data access, creating a seamless experience when retrieving data from distributed files.

Scheme Programming

Scheme is a functional programming language known for its minimalist design, which makes it suitable for data-directed programming. In this scenario, Scheme's flexibility and its powerful abstraction capabilities come into play significantly. With Scheme, you can define global structures and functions to handle diverse data structures, accommodating the unique needs of each division at Insatiable Enterprises.

The granularity of Scheme allows it to handle multiple data representations smoothly by utilizing dispatch tables. This mechanism helps in achieving uniformity across different divisions' files. Each division can maintain its unique setup, but the central system connects these through common interfaces. This is done by mapping division-specific identifiers to their respective data-access methods, which Scheme handles gracefully.

In our specific problem, procedures like `get-record` and `get-salary` become straightforward as they leverage Scheme's capability to dynamically select the correct processing function. This is achieved through a central dispatch table, allowing each division's file to be processed consistently, without altering individual division structures.

Information Retrieval

Information retrieval becomes both an art and science in decentralized settings like those at Insatiable Enterprises. While each division may have its own way of structuring data, the goal is to retrieve necessary information efficiently across this heterogeneous system.

The articulated challenge involves extracting a specific employee's record from numerous databases that vary from division to division. Through data-directed programming, this is possible by creating a uniform access point for record retrieval. By setting up dispatch tables, each division can register its record retrieval procedures, thus standardizing operations like `get-salary` retrieval across the entire system.

Moreover, when dealing with vast networks, the ability to find a record quickly becomes crucial. Instead of querying them one by one, function maps can be applied, using the `find-employee-record` to swiftly locate the desired information.

• Efficiency: Without centralized data, individual databases are searched more efficiently.
• Scalability: The network can handle new divisions and a vast number of employees with ease.
• Flexibility: Each division retains the flexibility of its data structure without hampering the whole system.