XLSXXLS

XLSXXLS is a proposed open specification for a cross-application spreadsheet format designed to improve interoperability among spreadsheet programs. The name suggests a synthesis of Microsoft's XLSX format and the longer-standing XLS lineage, signaling support for both modern and legacy workbook structures. It is described in speculative and collaborative discussions as an extensible, container-based format that can represent worksheets, formulas, charts, and embedded resources in a portable way.

Specification overview: XLSXXLS defines a ZIP-based container containing a manifest, one or more worksheet documents, and optional assets such as images or external data links. The core data model uses a combination of XML for deterministic structure and optional JSON for metadata and API bindings. It supports common spreadsheet features such as cell values, formulas with reference semantics, named ranges, data validation, conditional formatting, and charts, as well as pivots and basic macro-like scripting within a sandboxed environment.

Execution and safety: To address security concerns, formula evaluation is intended to be deterministic and independent of locale, with an optional sandbox for any executable scripts.

Compatibility and migration: XLSXXLS provides translation layers to convert between XLSXXLS and existing formats like XLSX and ODS, enabling import and export paths in adopter software. In addition, it proposes a clear versioning and feature negotiation mechanism to handle evolving capabilities.

Status: As a proposal, XLSXXLS has not been standardized by major standards bodies. Prototype implementations exist in some open-source projects and research efforts, but practical adoption remains limited and contested due to complexity and licensing considerations.