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STAM: Stand-off Text Annotation Model

STAM is a data model for stand-off text annotation. The underlying premise is that any information on a text is represented as an annotation. We define an annotation as any kind of remark, classification/tagging on any particular portion(s) of a text, or on the resource or annotation set as a whole, in which case we can interpret annotations as metadata. Additionally, rather than reference the text directly, annotations may point to other annotations (higher-order annotation). Examples of annotation may be linguistic annotation, structure/layout annotation, editorial annotation, technical annotation, or whatever comes to mind. Our model does not define any vocabularies whatsoever.

The underlying resource is taken in its most bare form without further information; e.g. plain text (an ordered sequence of unicode points). Any additional information would be considered an annotation in our model. Interpreting and supporting particular formats/encodings is up to the implementations and opaque to the data model.

STAM does not depend on other more complex data models such as RDF, W3C Web Annotations, TEI, FoLiA or whatever, but instead addresses the problem from a more functional and pragmatic perspective. We separate pragmatics from semantics and define a kind of lowest common denominator upon which further solutions can be built. The user is free, and in fact encouraged, to use vocabularies that are formalised elsewhere.

STAM is primarily intended as a model for data representation, and less so as a format for data interchange. It is designed in such as way that an efficient implementation (both speed & memory) is feasible. The form of such an implementation either in a relational database, triple store, directly modelled in memory, is left open to the implementation. Our model should also be reducible to a more generalised acyclic directed graph model without much difficulty.

Goals/characteristics of STAM are:

  • Simplicity - the data model must be easy to understand for a user/developer to use and only contain what is needed, not more. We provide a minimal foundation upon which other projects can build more complex solutions. These are deliberately kept out of STAM itself. The notion that everything is an annotation is at the core of STAM and one of the things that keeps it simple.

  • Separation from semantics - The data model does not commit to any vocabulary or annotation paradigm. It must be flexible enough to express whatever annotation paradigm a researcher wants to use, yet provide the facilities to be specific enough for practical purposes. The model basically allows for any kind of directed or undirected graph.

  • Standalone - No dependency on other data models (e.g. RDF) aside from Unicode and JSON for serialisation, no dependency on any software services.

  • Practical - Rather than provide a theoretical framework, we primarily aim to provide a practical specification and actual low-level tooling you can get to work with right away.

  • Performant - The data model is set up in such a way that it allows for efficient/performant implementations, with regard to processing requirements but especially memory consumption. The model should be suitable for big data (millions of annotations). We sit at a point where we deem to have an optimal trade-off between simplicity, flexibility and performance.

  • Import & Export - Reads/writes a simple JSON format. But also designed with export to more complex formats in mind (such as W3C Web Annotations / RDF) and imports from common formats such as CONLL. Note that although STAM puts no constraints on annotation paradigms and vocabularies, higher data models may.

The name STAM, an acronym for "Stand-off Text Annotation Model", is Dutch, Swedish, Afrikaans and Frisian for "trunk" (as in the trunk of a tree), the name itself depicts a solid foundation upon which more elaborate solutions can be built.


The following implementations are available:

  • stam-rust - A STAM library written in Rust, aims to be a full STAM implementation with high performance and memory-based storage model.
  • stam-python - A STAM Library for Python. This is not an independent implementation but it is a Python binding to the above Rust library.
  • stam-tools - A set of CLI tools for STAM.