LibreOffice 26.8 adds basic support for importing and exporting a range of chart types that Microsoft Office includes in OOXML files: box-and-whisker, funnel, Pareto, radial, treemap and waterfall charts. LibreOffice is unable to display or edit these charts, but it does recognise them, informs the user that the chart type is not yet supported, preserves the underlying definition unchanged, and rewrites it when the file is saved.
At first glance, this appears to be an admission of incompleteness, whereas it is actually an example of what implementing a proprietary format entails when the aim is interoperability – for the benefit of users, rather than a commercial strategy that treats users as mere tools.
What happened
Microsoft added these chart types to Office from 2016 onwards, storing them in a namespace generally referred to as ‘chartex’. The namespace is not part of the ISO/IEC 29500 text approved as an international standard, but is documented separately in Microsoft’s extension documentation.
This is entirely legal and perfectly normal commercial behaviour: a vendor improves its product and the file format evolves accordingly. The consequence, however, is that the format in everyday use is no longer the one that was standardised. The ISO number continues to be cited in tender documents and policy documents, but the files being exchanged are different.
For any implementer other than the vendor, this creates a permanent state of delay. This is not a one-off gap to be bridged with sufficient effort, but a structural delay, as the specifications are in the hands of a vendor that does not publish its release schedule, with priorities defined according to commercial criteria.
Three possible responses
An office suite that encounters a chart it does not recognise has three options:
- It can reject the file. This is an honest but pointless solution: the user is left with a document they cannot open and concludes that the software does not work.
- It can discard what it does not understand. The file opens, the chart disappears, and the user only realises this when the document is forwarded to a colleague and the chart is no longer present. This is the most damaging outcome, as the loss occurs silently and the blame falls on whoever opened the file last.
- They can retain what they are unable to display. The user is informed that this type of chart is not supported, so they see a placeholder rather than a blank space, and the underlying definition remains intact when the document is transferred from one application to another. The document is restored in full when returned to the source application.
LibreOffice 26.8 adopts the third option, the only one of the three that respects the fact that the document belongs to the user rather than to the software – or, indeed, to the company that develops the software.
Unfortunately, there is a limitation, and this is an exception. Charts with regional maps contain extensive geographical information that LibreOffice is unable to preserve. The chart type survives the import-export cycle, but very little of its content remains intact.
Why this is important beyond charts
The Chartex case is of limited scope. The model, however, is not.
All organisations whose documents are written in a format controlled by a single vendor accept a dependency they are unable to manage, because the specifications may change without notice, with the addition of features that are only understood by a single implementation.
Nothing untoward needs to happen for the organisation’s archives to become progressively more difficult to read by all other software.
The Open Document Format is not immune to change, but it changes differently. Revisions are proposed, discussed and approved by a technical committee at OASIS, whose work is public, and are published as version specifications that anyone is free to implement.
An implementer wishing to support ODF 1.4 can read the ODF 1.4 specification and put it into practice. This is the only difference, and it is sufficient.
The bidirectional preservation of unsupported features is what distinguishes a responsible implementation under current conditions, but it does not constitute an improvement on those conditions. LibreOffice is the only office suite to adopt this approach, in order to protect users and the content within their documents.