Methodology and meta-model
In addition to a set of maps, we also need a set of legends for these maps. For different sets of data, in order to read them, you need to have their data models. For example, for a database of information about concerts in Paris in the fall of 2022, we need a data model for such information, not just the information itself. We need a meta-model of concert information, not just the concert information itself. The combination of the multi-model with its defining meta-models will be called the mega-model.
If our role of interest is geographical, then it is represented by geographical descriptions - maps. For the geographical description/modeling of a hill in a neighboring village, we will need a variety of models (maps) that make up a whole atlas (multi-model). In addition to this, we will need to know what types of models should be in the atlas (for example, physical map, political/administrative map, map of mineral resources, population density map, flora map, fauna map, soil map, etc.), defined by meta-models (legends of the respective types of maps developed by geographers and usually available in culture, they can be "Googled").
If we need to model a hill near another village, we will have a different multi-model while retaining all the same meta-models. Only the mega-model can be considered and discussed as a whole: without discussing the types of maps, agreeing on symbolic representations on these maps, and other aspects related to meta-modeling, discussing maps is not possible. If you didn't agree on the language in which you write project documentation (Chinese, Swahili, or Romanian), you may need to rewrite it - but before rewriting, you still have to agree on the language. If you didn't agree on the format for presenting the profit and loss report, you may need to rewrite it, but before the correspondence, you still need to agree on the meta-model from the financial description method - what format of the profit and loss report needs to be provided. Modeling without knowledge of the meta-model and agreement on what it can reflect about the subject of interest of the project role is impossible. If you don't know the types (don't have education, for example), didn't find the necessary textbook, and made up the meta-model "off the top of your head," "on the fly," didn't document the meta-model - there will be endless failures due to the inability to explain the meanings of important characteristics reflected as objects of bad or completely unknown/unintelligible types. " - Petka, instruments! - Eight! - And why eight?! - And what are the instruments For?!".
When learning modeling, they teach not models (the model will be new each time for each new system!), they teach a set of types of a meta-model, objects for which need to be able to find in the subject area of interest. This set of types, that is, the meta-model, will be the same for different models. If you didn't model a certain object - then you couldn't later reason using it, missed something important in the project.
They teach modeling methods - they will be the same for different systems, they will help take into account the interests of the same project roles, although different people will play these project roles in different projects - knowledge of meta-models helps transfer the experience from project to project about what is important in the system and what satisfies the interests of the project roles. You learn 3D or even 4D modeling of engineering systems once, then use this modeling skill in a variety of projects.
If you give someone a system description, you must also indicate how you obtained this description, specify the method used, define the types of important objects reflected in the model. You must understand that this description is the result of modeling, so it should only contain important facts for the project role to which you give this description, and should not contain anything else that would be informational noise for this project role. If you can't say what method you used to describe the system, if you don't know if this method reflects the subject of interest of the project role, you are making a mistake, this mistake will cost you dearly.