Martin Soukup

Fundamentals of Persistence

This chapter is the heart of the book. It explains algorithms, technical details and programming tricks of various approaches to implementation of persistent data—binary and ASCII serialization, memory paging, disk paging and smart pointers. The last section presents QSP (Quasi-Single-Page), a new design of persistent data which, besides other languages, also works in Objective-C and with iPhone applications.

Automatic Persistence for Objective-C

This chapter describes the implementation details of the QSP persistence. It starts with a single page from which all the objects are allocated. When more space is needed, additional pages are automatically allocated. When storing data to disk, all data are collapsed into a single page, and the unused objects are eliminated. During each program run a temporary management of free objects is used.

Languages, Their Features and Limitations

The implementation of persistence and class libraries depends on features provided by the programming language. Even though C, C++, C#, Objective-C and Java are quite similar in many aspects, they are significantly different in what they allow us to do about persistence and class libraries.

Proposal to Add a Keyword to All OO Languages

Implementation of libraries that can handle bi-directional associations today requires a simple code generator. This code generator could be eliminated if the programming languages supported a new keyword described in this proposal.

Data Structures, Patterns, and UML

An essential part of every persistent system are persistent class libraries. Existing class libraries have two flaws: They cannot store bi-directional associations, and they do not treat associations (relations) as first class entities. We need a new paradigm for the proper design of these libraries. We will treat data structures as a database, and implement databases as data structures. The architecture will be controlled by a textual schema, not by the UML class diagram. However, this diagram will be automatically generated from the textual schema. This is just the opposite to what probably expect.

Advanced Features, Schema Migration

Advanced features involve both persistence and data structures. Schema migration deals with changes of classes and their relations when storing data to disk. Extensible property allows one to add class members without changing the class declaration. We also discuss multi-user access to persistent data, ASLR and storing objects in flash memories and smart phones.

The popularity cycle of graphical tools, UML, and libraries of associations

A historical cycle has been observed where the use of graphical tools becomes critical to software development but these tools eventually fall from use as the underlying cause of complexity is removed through a new programming paradigm. This workshop attempts to take a unified view of UML-related ideas which span from high level software design (UML and MDD) to technical details of implementing reusable associations. It also identifies gaps in the existing programming languages addressed by UML class diagrams. The discussion is not language specific and applies to both C++ and Java. For additional details see www.codefarms.com/OOPSLA07/workshop.