Alan Dearle

In orthogonally persistent systems, data is treated independently of its persistence allowing
storage management details to be ignored by programmers. The coexistence
of all data within a persistent repository provides new opportunities
for the persistent environment to participate in a number of software
engineering processes, namely, software: o construction, o debugging,
o maintenance, o evolution, and o distribution. A novel programming methodology
supporting various styles of binding allows the persistent environment
to participate in the software construction process. Existing programs
and data may be bound to an application at different times during the
application’s lifetime, namely, at run-time, compile-time and program
construction-time. This wide range of binding styles enables the programmer
to trade off binding safety and binding flexibility. A mechanism called
Octopus enables the programmer to access a rich source of information
about the bindings within arbitrary values. Using this information, existing
applications may be interrogated and manipulated in ways in which the
programming language alone would not normally permit. However, Octopus
ensures that the type system of the programming language remains inviolate,
thus providing a type safe mechanism for constructing debugging, maintenance
and evolutionary tools. Another feature of Octopus is that it permits
portions of an application’s object graph to be isolated and transmitted.
Nodules permit a style of template programming that enables data values
and executable code to be shared between different Nodule instances. The
essence of this mechanism is to allow programs to be constructed and compiled
without the requirement that the values used by the program be present.
In this manner, individual components may be constructed independently
and later assembled to form a complete application. Nodules also provide
a rich source of information about the structure of an application and
may be used in conjunction with Octopus to develop and maintain software
components. This thesis describes in detail a persistent programming environment,
the Octopus and Nodule mechanisms, and illustrates how each of these mechanisms,
when used in conjunction with each other, provide a persistent integrated
programming environment that supports a wide variety of software engineering
activities otherwise lacking in conventional, or non-persistent systems.