Automation Endpoint (AE)

Servers or containers that execute a client-side workflow for configuration and deployment of an application or service on a target machine. They contain the automation scripts and their corresponding orchestration tools (for example Ansible, Terraform, Packer, Powershell,…).

Application (app)

Software entity, potentially distributed, that fulfills a larger use-case and results from linked (micro)services and the functional, non-functional and extra-functional requirements. In effect, the executing parts of a stack instance on the IT infrastructure.

Services (srv)

Software entity that performs a small piece of functionality and has a clear set of service requirements. A constituent part of an application.

Service Requirements

The functional and non-functional dependencies a service has so it performs as desired.

Functional Requirements (FR)

The configuration packets required of the operating environment for the the service to perform its functions, such as a Linux OS, DNS or Web configuration, or nginx.

Resource Requirements (RR)

The resource requirements to run the service such as CPU, memory, hard disk capacity, and so on.

Policies (POL)

Service and application requirements that give additional specifications for how the service or applications functions. These map to behavioural constraints on and across services, such as high availability of a service through redundancy or a low latency requirement between two services.


A declarative description of an application and the IT infrastructure it may run on. It consists of a SAT and SIT but is not necessarily realisable. A realisable (i.e., solved) Stack is called an ST.

Stack Application Template(SAT)

Template that models the application as a set of services with their requirements, links and any policies.

Stack Infrastructure Template (SIT)

Template that models IT infrastructure as infrastructure targets originating from the environment, location, and zone and possessing a set of infrastructure capabilities.

Infrastructure Targets

A part of the IT infrastructure, a virtual or physical entity capable of executing software (VM’s, desktop computers, …), that can be targeted to run services.

Infrastructure Capabilities

A set of properties that the infrastructure has, such as specific software, CPU, memory, and so on.

Stack Templates (ST)

Template that models a stack as a deployable set of services matched to suitable infrastructure targets. It contains all viable solutions resulting from merging the SAT and SIT at a certain point in time.

Stack Instance (SI)

An instantiation of one of the viable solutions of a ST on the IT infrastructure.


An atomic unit of work, done completely or rolled back, given by an Operator to STACKL for processing. E.g., create a stack instance.

Task Broker (TB)

The pluggable module in STACKL that manages the end-to-end life cycle of tasks ensuring they are done completely or rolled back

Message Channel (MC)

The messaging system used by STACKL to communicate with other entities for processing tasks, such as Agents or Workers.


Entities that take care of the client-side execution of tasks given to STACKL. This is mainly the instantiation of stacks instances through automation endpoints on the client’s IT infrastructure.


The entity that gives work to STACKL. For instance, a user doing a REST API call through the web interface to create a stack.


The entity that accepts or takes work, in the form of tasks, from STACKL and processes it to a desired state, including storing it or communicating it to other entities.


The pluggable storage module in STACKL that processes, retrieves and stores documents.


A JSON or YAML-based file with a specific type that models IT infrastructure building blocks, application service definitions, and their configuration data.


Category of types for documents that represent a tangible part of the clients IT domain. This can be infrastructure targets, services, or applications/stack-instances and is the result of the hierarchical key/value merging of its constituent sub-parts. For instance, an infrastructure target is the result of an environment, location and zone with a certain hierarchical relationship.


Category of types for documents that model elements related to the clients IT domain. Such as allowed types, authentication documents, etc.

Deprecated terminology for old users of STACKL

Resources → Services, inline with the microservice architecture approach

Roles → Functional Requirements (i.e., configuration packets for machines so that they can perform certain functions)

Shape → Resource Requirements

Proxy → Now Agents

Last updated on February 10, 2020