---++ Introduction

The ATerm (Annotated Term) Format is a format for exchanging structured data between tools. The ATerm format is a generic internal and external representation of data by means of simple prefix terms.

---++ Abstract Data Type

An ATerm is an expression according to the following grammar:
<verbatim>
  t  := bt					  -- basic term
		 | bt { t }			 -- annotated term

  bt := C						-- constant
		 | C(t1,...,tn)		-- n-ary constructor
		 | (t1,...,tn)		 -- n-ary tuple
		 | [t1,...,tn]		 -- list
		 | "ccc"				 -- quoted string
		 | int					-- integer
		 | real				  -- floating point number
		 | blob				  -- binary large object
</verbatim>
Here =C= is a constructor name, which is either an identifier or a quoted string. 

---++ Format

ATerms can be exchanged in several formats:
	* The Binary ATerm Format (BAF) is an efficient format that preserves maximal sharing.
	* The Textual ATerm Format (TAF) preserves maximal sharing but is not as efficient as BAF.
	* The plain text format (TEXT) is a textual format that does not preserve maximal sharing.

The ==baffle== tool in the [[ATerm Library]] can be used to convert the formats.

---++ Library

The ATerm Format is supported by [[ATerm Library][ATerm Libraries]] for C, Java, and Haskell.

---++ Application

The ASF+SDF Meta Environment operates on AsFix representations of source code in the ATerm format.

The [[Stratego.WebHome][Stratego]] program transformation language uses ATerms to represent abstract syntax trees:
	* Specification defines transformation of ATerms
	* ATerm library is used in implementation of terms
	* Exchange of syntax trees as ATerms

---++ Publications

The ATerm format is described in the following publication:
	* M. G. J. van den Brand, H. A. de Jong, P. Klint, and P. A. Olivier. [[Transform.EfficientAnnotatedTerms][Efficient Annotated Terms]]. _Software - Practice \& Experience_, 30:259-291, 2000.