Office Open XML L Annex L. (informative) Primer L.5 Introduction to VML L.7.3 Future Extensibility L.7.3.4 Future Extensibility Constructs L.7.3.4 Future Extensibility Constructs The two extensibility constructs used to represent extensions in OOXML schemas are: Subsections L.7.3.4.1 extLst L.7.3.4.2 AlternateContent Blocks Last updated on March 14, 2025 L.7.3.4.1.3 Example