Alistair Miles

Category: oais

On the OAIS Information Model as a Platform-Independent Model (PIM) in a Model-Driven Software Architecture

Abstract

This short paper summarises some work done on the possibility of using OAIS information model as a basis for the model-driven design and implementation of components within a digital preservation software architecture. Two model transformations were defined using the Enterprise Architect template language. The first model-transformation transforms a platform-independent UML class model (PIM) into a set of UML interfaces specific to the Java 1.5 platform (here called a Java API model). The second model-transformation transforms a platform-independent UML class model (PIM) into set of UML classes specific to the Java 1.5 platform, implementing the interfaces generated by the first model-transformation (here called a Java implementation model). Both were applied to the OAIS information model as PIM, and the generated models are presented here with discussion.

Read the rest of this entry »

The OAIS. Information Model Revisited Part 3. Towards Models for Interpretation/Virtualisation Recipes

In this note, I begin to explore the use of the Eriksson-Penker UML extensions for business process modeling, as a tool for modeling the processes or work flows required to successfully interpret or virtualise a digital object.

Previously, in part 1 of this series, I explored the abstract notions of data, information, representation information and interpretation, as defined by the OAIS Information Model. In part 2, I tried to apply these notions to a simple example of a Web page. I found that we need to go beyond the OAIS Information Model if we want to capture and represent the “recipes” that take you from a sequence of bits to something more useful, in the general case where there may be multiple steps or stages required to process, virtualise or render a digital object.

Recipes and Dependencies

Take again the example from part 2 of a simple Web page, encoded as an XHTML 1.0 Transitional document using the UTF-8 character set, and stored as a single sequence of bits.

I’m interested in modeling the “recipe” that tells me how to turn the encoded sequence of bits back into a Web page, because this recipe will define the “dependencies” for the preserved object. By “dependency” I mean those items of information and/or software that are required to execute the recipe — the ingredients and utensils, to use the cooking analogy. Note that by “execution” I do not necessarily mean execution by a computer — steps in a recipe might well be entirely manual.

If I knew what these dependencies were, I could then compare them with the knowledge and software currently held by the designated community (DC), and decide which of the dependencies also need to be preserved.

I could also design a system which computes any “gaps” that arise between the knowledge and software held by the designated community and those required for execution of the recipe. This is one of the goals of the CASPAR project.

Read the rest of this entry »

The OAIS Information Model Revisited — Part 2.

Previously, in The O.A.I.S. Information Model Revisited – Part 1, I explored the abstract notions of data, information, representation information and interpretation.

I found that the O.A.I.S. notion of interpretation makes most sense when viewed as an act or operation, taking data and representation information as input, yielding new information as output.

In this note, I’d like to explore these ideas further, and see how they related to some real world examples of digital preservation.

Recipes” for Interpreting Archived Data

In particular, I’m interested in the “recipes” that tell you how to convert a sequence of bits into something more useful.

This is a fundamental requirement for any preservation archive – when retrieving an archived information item, you need the bits that encode that information, but you also need to know how to turn those bits into something else, something you can use.

The O.A.I.S. Information Model acknowledges this, by highlighting the need for representation information, but does it go far enough? Does the model really help us to understand the problems of reconstructing a useful artefact from an archived sequence of bits?

Read the rest of this entry »