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This file is part of Logtalk <https://logtalk.org/>  
Copyright 1998-2021 Paulo Moura <pmoura@logtalk.org>  
SPDX-License-Identifier: Apache-2.0

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
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To load this example and for sample queries, please see the `SCRIPT.txt` file.

This folder contains Logtalk versions of two examples of network modeling
for recognizing polyhedra represented as graphs as described in the following
paper:

	@inproceedings{Markov1989AFF,
		title={A Framework for Network Modeling in Prolog},
		author={Z. I. Markov},
		booktitle={IJCAI},
		year={1989}
	}

A copy of the paper can be downloaded from:

	https://www.ijcai.org/Proceedings/89-1/Papers/013.pdf

The Logtalk versions of the examples use parametric objects and the
coroutining library to approximate the semantics of the original examples.
The object parameter variables approximate the concept of "net-variables"
described in the paper. The implicit use of the `dif/2` constraint is
mentioned in the paper third page: "(The use of a special Prolog extension,
ensuring all different variables to be bound to different objects, is
essential in this example. Such an extension is also available in
Prolog III.)".

Note that the use of the coroutining library limits the backend Prolog
systems that can be used to run this example to ECLiPSe, SICStus PRolog,
SWI-Prolog, and YAP.
