There are a few commonly-overloaded terms which refer to specific things in the LIT APIs and codebase:

  • Component, a backend component in Python. Includes things like counterfactual generators, metrics classes, UMAP and PCA implementations, and salience methods.

  • Element, a Web Component or another HTML element. The client/elements/ folder contains many custom elements used for visualizations and parts of the UI, but which are not full-fledged LIT Modules.

  • Example or Datapoint, an element of a dataset - the things that we feed to models and get predictions back.

  • Instance, a specific implementation of LIT (e.g. a binary) or server job running the former.

  • LIT, the Learning Interpretability Tool. Always fully capitalized, sometimes accompanied by a 🔥 emoji. Pronounced “lit”, not “ell-eye-tee”. Formerly known as the Language Interpretability Tool.

  • Lit, the web framework consisting of lit-element and lit-html and maintained by the Polymer project. LIT is built on this framework, but the naming is coincidental (we like it, of course).

  • Model, a machine-learning model that we’re exploring or debugging with LIT. Doesn’t need to be a single neural network; could be a pipelined or composite system, and may be hosted remotely.

  • Module, a frontend visualization module (see Frontend Dev Guide). Strictly speaking, this is something that inherits from LitModule, renders a part of the UI, and interacts with the frontend framework. Usually found in client/modules/. All modules are elements, but not all elements are modules.

  • Potato (noun or verb), a frontend error. See

  • Server, the Python backend. A WSGI application that provides a handful of HTTP endpoints to serve models, datasets, and other components.

  • Service, a part of the frontend framework that handles state and provides helper methods. Most of these are global singletons, with the notable exception of SelectionService which is duplicated when in example-comparison model.

  • Slice, a set of examples from a dataset. Often created by Faceting along a specific feature.

  • Widget and Widget Group, elements of the frontend layout. A Widget is a thin wrapper over a Module, and a Widget Group contains one or more widgets along with header bars, resize, and minimize/maximize controls - roughly, like a regular GUI window. Sometimes we refer to a widget or a widget group as a Panel.