Our initiative aims at designing a controlled vocabulary for the description of the layout of textual sources: SegmOnto. Following a more physical approach rather than a strictly semantic one, it is designed as a pragmatic and generic typology, coping with most of the Western historical documents rather than answering specific needs. The harmonisation of the layout description has a double objective: on the one hand it facilitates the mutualisation of annotated data and therefore the training of better models for page segmentation (a crucial preliminary step for text recognition), on the other hand it allows the development of a shared post-processing workflow and pipeline for the transformation of ALTO or PAGE files into DH standard formats, which preserves as much as possible the link between the extracted information and the digital facsimile. To demonstrate the capacity of SegmOnto to answer both these objectives, we aggregate data from multiple projects to train a layout analysis model, and we propose a prototype of a generic pipeline for converting ALTO-XMLs into XML-TEI.