## 1 Introduction
Due to all the issues listed in Table 1, the c4c Paediatric Data Interoperability Working Group (PDIWG) strongly recommended future versions of the CCPDD use a more formalised modelling approach to defining the data structure. In contrast to clinical research, methods and tools to formalise clinical models (data structures and semantics) that define documentation patterns for the consistent population and interoperable communication of EHRs are well established [11]. The openEHR archetype concept is the oldest and most mature formalism for this [12,13]. In more recent years, other initiatives have adopted similar approaches [14], and quality processes for developing clinical models have also been published [15,16]. This clinical modelling paradigm has been an ISO standard since 2008--most recently published as ISO 13606 Part 2 [17]--which enables clinical models (archetypes) to be defined as use patterns of an underlying semantics-free reference model defined in ISO 13606-1 [18]. Clinical modelling tools have been used extensively by EHR interoperability communities globally in order to help them to define models that are technically and semantically aligned with an underlying reference model and offer a number of user features to facilitate good quality model development [19]. Mapping transformations have been defined between archetypes based on ISO 13606 and the CDISC Operational Data Model (ODM) standard most often used for clinical trials data [20]. There remains, however, an evidence gap in terms of the incorporation of the archetype approach within regulated clinical trials by leveraging this computable knowledge representation as a source for eCRF generation and CDISC ODM mapping. c4c therefore elected to pilot the use of the archetype approach--based on the \begin{table}
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**Issue** & **Explanation** \\ \hline \multirow{6}{*}{Version control} & As the Cross Cutting Headatric Data Dictionary (CCPDD) grew and new versions were developed, there was a risk that obsolete versions of it were used. The size of the concert4 children (c4c) consortium made this more likely. \\ \hline \multirow{6}{*}{Complexity} & As the CCPDD grew, it became more cumbersome to manage. Adding new worksheets to the spreadsheet made the document less user-friendly. \\ \cline{2-3}  & Risk of data dictionary concepts being modelled differently in different domains by different teams. \\ \hline \multirow{2}{*}{Linkage} & Due to the flat structure of Microsoft Excel, it was challenging to show nested structures and interlinking items. \\ \hline \multirow{6}{*}{Semantic detail} & Not all structure and semantic specifications can be captured, and there was no way of prompting authors about missing data properties. \\ \hline \multirow{6}{*}{Usability} & As the CCPDD grew, visualisation became increasingly important to help users to understand what the dictionary contains, and what they were now in the process of authoring. This functionality was not possible in Microsoft Excel. \\ \hline \multirow{6}{*}{Only one standard used (CDISC)} & Predominantly focussed on one standard (Clinical Data Interchange Standards Consortium (CDISC)): this reduced opportunities to link items to data from electronic health records. \\ \cline{2-3}  & The Microsoft Excel version required transcription into electronic case report form (eCRF)-generating tools. \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Challenges of using a Microsoft Excel spreadsheet to represent the CCPDD. ISO 13606 standard--to reformulate and to better formalise its initial CCPDD, including the export of these paediatric research archetypes into a CDISC ODM format and the automated configuration of eCRF templates. The scope of the problem under investigation was whether it was possible to robustly and methodically structure the content of the CCPDD into an environment that was not compliant with clinical trial standards alone.