As the name implies, a lump assembly is an assortment of lumps arranged into an assembly (inside a folder). It is also possible to include a hierarchy of folders inside a Lump Assembly (therefore puting lumps into “namespaces” where they can have a load order implied; see below). It is even possible to nest wads inside an assembly.
The automatic loading of data files can be utilised to load directories that contain individual data_lumps. This kind of a directory is called a “lump assembly” and it can be used instead of a wad file. Note that a lump assembly can only be loaded via the autoload mechanism (but it can be inside a pk3 that is loaded manually).
The assembly can be built using a hierarchy of directories. For example the contents of a pk3 might be:
#assembly/ data1.lmp data2.lmp powerplant.2/ a-E2M3.lmp b-THINGS.lmp xyz.lmp
#assembly would be mapped to Data\<Game>\Auto\assembly\.
By default, the contents of a lump assembly are loaded in alphabetical order. However, some kinds of data require that the lumps are in a specific order (for instance map data). You have two options if you want to enforce a specific order:
The first three characters of the file name are ignored (“01_”) and LUMPNAME becomes the name of the lump.
The order in which assemblies are loaded is governed by the autoload mechanism. In short, all folders and files inside the Auto folder are loaded in alphabetical order. Note that this means that it makes no difference in which order the files containing the assemblies were loaded.