O PAPERS 1 OF 6 Managed Data: Modular Strategies for Data Abstraction

Managed Data is a two-level approach to data abstraction in which programmers first define data description and manipu- lation mechanisms, and then use these mechanisms to define specific kinds of data. Managed Data allows programmers to take control of many important aspects of data, including persistence, access/change control, reactivity, logging, bidi- rectional relationships, resource management, invariants and validation. These strategies for implementing these features are implemented once as reusable modules. Managed Data is a general concept that can be implemented in many ways, including reflection, metaclasses, and macros. In this paper we argue for the importance of Managed Data and present a novel implementation of Managed Data based on interpreta- tion of data models. The paper also discusses strategies for implementing Managed Data. In object-oriented languages, Managed Data typically requires programmer control over the meaning of the field/method access operator (the "dot" operator). Bootstrapping poses difficulties, because imple- menting the first data manager requires some data. As a case study, we used Managed Data in a web development frame- work from the Ens¯ o project to reuse database management and access control mechanisms across different data defini- tions.