The formal approach to systems modeling offers a sound theoretical basis for modelling any universe of discourse and enterprise. In the approach the combined use of object and transition system specification techniques has been well established.
Since many years already, UML domain modelling techniques  offer a standard for modelling the entities that occur in the universe of discourse associated with any service or information system. The possible states of a (work) system and (relevant parts of) its environment are represented by a (possibly large) set of object-diagrams (or token models), in which each object is instance of one or more classes. Any information system will include representations of those entities and of relevant events involving them.
Umbrello UML Modeller is a convenient open source tool for making UML models.
There exist several tools to capture the enterprise models that support people to plan and implement change in their livelihoods. The (EA)2 approach  illustrates practices applying the Sparx Enterprise Architect tool.
As an Enterprise Architecture practice is very content intensive, the costs for implementing such an approach "singly and severally" becomes high,.. too high or prohibitive for many.
Doing enterprise architecture in a multi-level perspective implies enormous content-reuse opportunities. The Wikiworx systematized content commons which include this Ens Dictionary offers some of the components that will enable us to collaboratively achieve those reuse benefits.
We use Archi - The Free ArchiMate Modelling Tool for creating and sharing the models that we make for the Addis Ababa Action Agenda. For these enterprise architecture models we apply the layers and aspects of ArchiMate Framework and the (scope) levels of Federal Enterprise Architecture Framework.