Data format translation and migration Future possibilities Alasdair Crockett, Data Standards Manager UK Data Archive

Past problems and future solutions Past/existing problems – ‘skeletons in the back catalogue’. The UKDA and other long-standing archives have old studies in column binary or other legacy formats that are difficult, time consuming and occasionally practically impossible to process/migrate. Future solutions – to ensure that we don’t store up similar problems (with vastly increased amounts of data) in 20 or 30 years time This talk covers Future Solutions

When does data format translation occur? To enable data processing (validation, etc.) From ingest format to “processing format” (this being SPSS in the case of the UK Data Archive) To ensure long-term preservation From processing format to preservation format(s), these being SPSS portable and tab-delimited text (with data dictionary) in the case of the UK Data Archive. To achieve user-friendly dissemination From preservation or processing format to dissemination format of user’s choice e.g. STATA, SAS or EXCEL, in addition to the ubiquitous SPSS. Migration when previously mainstream formats become obscure or new formats are requested by users

What are the potential problems of data format conversion? At time of processing: Rounding/truncation of numeric data Truncation of textual data Differences in handling “internal” metadata (differential label lengths, missing value handling, etc.) Corruption of specially formatted variables (especially date/time variables) Embedded special characters (line feeds, carriage returns, tabs, etc.) Migration: … all the above and added problems with Dealing with out of date, unfamiliar and/or, inaccessible formats (e.g. column binary)

The ‘Data Curation Initiative’: An XML standard and conversion utilities for survey data The ‘Data Curation Initiative’ (DCI) consists of: XML Standard: –Open standard for sharing and preserving datasets –Implemented as an XML Schema –Stores all attributes of a survey dataset – labels, missing value definitions, variable level notes, etc. Conversion software: –From proprietary formats to DEI (with no data loss) –From DEI to proprietary formats (text file +command file) –File and variable level metadata import/export to DDI XML schema

SPSS STATA SAS EXCEL ACCESS Data in DCI XML format SPSS STATA SAS EXCEL ACCESS DATA PRESERVATION DCI XML file provides preservation master copy of the dataset The key functions of the data curation software: Text file giving variable-level report of any data or metadata loss on export File and variable level metadata exported to DDI XML file RESOURCE DISCOVERY (METADATA EXPORT)

Migration strategy An approach such as the data curation initiative allows either: Traditional migration strategies – systematic migration of whole collection on preservation server Migration on request – preservation version remains the same but on-the-fly export utilities are updated to cater for new versions/formats as they become popular

Doesn’t the DDI do this? Not so far Could build onto the DDI – in any case the DCI will populate variable level of DDI Some advantages to keeping ‘data’ and ‘metadata’ separate: –Single xml file could become enormous and slow to parse –Allows communities who don’t use the DDI to use the DCI (and vice versa)