Fellow library code wranglers,
Coding questions don't come up often here, but I think this might be the best group to ask, as my question somewhat involves both coding and the nature of metadata and data. A considerable amount of my work involves ingesting materials into our institutional repository. We get this material from many sources in many formats; PDF, Quicktime, WAV, etc., with metadata in XML, MARC21, or even spreadsheets. It might be organized as filesystem directories, zip files, or images with imbedded metadata. Before loading into the repository, the metadata must be extracted and transformed, and the data files reorganized for convenient ingest.
To make this easier, we have written a toolkit (in Ruby) which handles the conversion. You select the source type (e.g. zipfile of electronic theses from Proquest), specify the directory/zipfile/whatever containing the data, and the toolkit executes all the transforms and organizes into a convenient directory structure, ready to ingest into the repository. The problem is that the code in the toolkit is clunky, making it difficult to add new sources and the needed transformations.
I am rewriting the toolkit from scratch, with a modular design. I want a consistent set of methods defined in an abstract class for a package of data (which I am calling a Tree), with subclasses defining the exact behavior of the methods for directories, zipfiles, images with imbedded metadata, etc. I'm sure this is familiar to some of you. A file or directory (or analog) within a Tree is defined as a path from the root of the Tree
The question I have is the best model to use for the arguments of the methods of this class. For instance, I want an analog to the copy method, to copy a file from the input Tree to the new ingest Tree. The ruby filesystem copy method is .cp(src, dest). An analog method would have to specify the input Tree along with the input path, and the output Tree plus the output path. So I could define the method as Tree.cp(srctree, srcpath, desttree, destpath). Or I could go a little more abstract and define a class Node which is a combination of a Tree and a path. Then I could create Tree.cp(srcnode, destnode), which looks more like the familiar filesystem methods.
Does anyone have an opinion on which would be better? Using Nodes looks a lot cleaner and appeals to my sense of organization. I will be defining a Tree.glob method, so that should handle instantiating source Nodes, but output Nodes would need to be instantiated. The first method avoids the complication of instantiating Nodes before using them in copy and move commands. I'm not sure which would be easier for writing specific ingest routines for a new data source, since someday someone else will have to write them. Any thoughts?
Steve McDonald
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