Tabular Data, Representation, Storage and Ingest

This section explains the basics of how tabular data is handled in the application and what happens during the ingest process, as the files uploaded by the user are processed and converted into the archival format in the Dataverse application.

What Happens During this “Ingest”?

The goal of our ingest process is to extract the data content from the user’s files and archive it in an application-neutral, easily-readable format. What does this mean? - Commercial applications such as SPSS and Stata use their own, proprietary formats to encode their files. Some companies publish the specifications of their formats (Thank you Stata - much appreciated!), some don’t (SPSS - yes, we are still frowning at you here at the Dataverse Project). Either way, reading these specially-formatted files requires some extra knowledge or special software. For these reasons they are not considered idea for the purposes of archival preservation. Dataverse stores the raw data content extracted from such files in plain text, TAB-delimited files. The metadata information that describes this content is stored separately, in a relational database, so that it can be accessed efficiently by the application. For the purposes of archival preservation it can be exported, in plain text XML files, using a standardized, open DDI Codebook format. (more info below)

Tabular Data and Metadata

Data vs. Metadata

A simple example is a numeric data column in a user’s Stata file that contains 0s and 1s. These numeric values will be extracted and stored in a TAB-delimited file. By themselves, if you don’t know what these values represent, these 1s and 0s are not meaningful data. So the Stata file has some additional information that describes this data vector: it represents the observation values of a variable with the name “party”; with a descriptive label “Party Affiliation”; and the 2 numeric values have categorical labels of “Democrat” for 0 and “Republican” for 1. This extra information that adds value to the data is metadata.

Tabular Metadata in Dataverse

The structure of the metadata defining tabular data variables used in Dataverse was originally based on the DDI Codebook format.

[TODO: a brief explanation of the DataVariable and related objects? A link to a more technical documentation writeup in the developers guide?]