Language of the framework.

Complete set of technical components on which a digital system operates, from physical infrastructure (servers, networks, energy) to the business logic the user perceives. The word means, literally, «pile»: these components rest on each other and dependence is directional — whoever controls the deep layers ultimately controls what the upper layers can do. When the document speaks of the global stack it refers to the set of platforms, models, compute infrastructure and protocols on which the digital world effectively operates today: a handful of companies, almost all American, some Chinese, none Latin American. When it speaks of the double stack it refers to the framework's central idea: the technological modernization of a nation, company or person requires distinguishing what is contracted from the global stack from what must be built and operated locally.

In Latin American colloquial use, especially in business, «infrastructure» is frequently used as a synonym for hardware and telecommunications — servers, networks, data centers, physical equipment. The framework uses the term in a broader sense, the technical-architectural sense of the last fifteen years: infrastructure also includes orchestration layers, shared base services, common processes and interoperability rails on which multiple applications are built. When the document speaks of horizontal infrastructure or horizontal stack, it doesn't refer to compute centers: it refers to the shared functional layers that multiple sectors and applications consume — interoperable digital identity, payment rails, modernized public registries, data exchange protocols. PIX in Brazil is infrastructure in this sense, not hardware: it's a functional rail on which thousands of applications operate. The distinction between infrastructure as physical object and infrastructure as shared functional layer is critical to understand principles 1 and 3.

A rail is a standardized circulation route: a shared and neutral infrastructure on which multiple actors can operate under common rules, without each having to build their own route. The metaphor comes from the railway — rails that are there, that any authorized train can use, on which trains with different destinations circulate. PIX is a payment rail: the infrastructure on which Brazilian banks make transfers, without each having built their own system. India Stack is a set of rails: identity, payments, data exchange. When the document speaks of building national or regional horizontal rails, this is what it refers to: common routes on which multiple applications, sectors and actors can operate with genuine interoperability. A well-designed rail multiplies all applications built on top of it. A rail handed to a single provider is a permanent capture point for all traffic that circulates above.

Functional level within the stack that fulfills a specific purpose. The framework's most important distinction is the difference between execution layer (where the system processes, computes, executes tasks) and decision layer (where criteria, rules, taxonomies and thresholds the system applies when executing are defined). The distinction is technical but also political: a nation or company can contract the execution layer without surrendering the decision layer, and that difference is the column of the entire framework.

Classification: the set of categories a system uses to organize the world. When a scoring system decides who is «high risk» or «low risk», it is applying a taxonomy. When a tax agency decides what counts as a «suspicious return», it is applying a taxonomy. Taxonomies are not neutral: they carry assumptions about the world, political values, and frequently biases inherited from whoever built them. That's why the framework insists that the decision layer — where taxonomies live — must remain under sovereign control.