Adelfa is an interactive proof assistant for reasoning about
specifications written in the Edinburgh Logical Framework (LF).
Adelfa is based on a new logic named 𝓛_{LF} whose atomic
formulas
represent typing judgements in LF and in which complex formulas can be
constructed using the usual collection of propositional connectives and
quantifiers over variables representing LF terms and
contexts. Quantification over terms is qualified by *arity types*
that indicate functional structure but that leave dependency information
to the domain of the body of the formula.
Context quantification is governed by a special kind of type, referred to
as a *context schema*, that describes a finite collection of patterns
of declarations out of which an instantiating (ground) context may be
constructed.
The meaning of formulas in this logic is described by using derivability
in LF to determine the validity of ground atomic formulas and attributing
a substitution semantics to the quantifiers.
Complementing the logic is a proof system that provides the basis for
establishing the validity of formulas in the logic.
Particular proof rules in this proof system embody a means for carrying
out case analyses relative to LF derivability and for reasoning
inductively over the heights of LF derivations.
The logic also provides a flexible basis for additional rules, such as
ones that encode meta-theorems related to derivability in LF. Adelfa
implements a collection of such rules as well.

An expository presentation of Adelfa can be found in the paper entitled "Adelfa: A system for reasoning about LF specifications." The reader may also consult a walkthough of a development that we have provided on this page and also some of the small, but growing, number of reasoning examples that are currently available. A detailed theoretical development of the logic underlying Adelfa is to be found in the paper entitled "A logic for reasoning about LF specifications."

The current working version of Adelfa can be obtained by downloading this tarball.

- The Adelfa reference guide has a brief description of the system syntax and tactics.
- A first walkthrough of an example Adelfa development is available for new users.
- Further examples are included in the distribution of Adelfa.

Work on Adelfa was supported by the National Science Foundation under Grant No. CCF-1617771. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author and do not necessarily reflect the views of the National Science Foundation.

The views and opinions expressed in this page are strictly those of the page
author(s). The contents of this page have not been reviewed or approved by the
University of Minnesota.