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Stochastice Performance Logic is a formalism for capturing performance assumptions. It is, for example, possible to capture assumption that newer version of a function bar is faster than the previous version or that library foobar is faster than library barfoo when rendering antialiased text. The purpose of this framework is to allow evaluation of SPL formulas inside Java applications.

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/*
 * Copyright 2015 Charles University in Prague
 * Copyright 2015 Vojtech Horky
 * 
 * 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.
 */
package cz.cuni.mff.d3s.spl.formula;

import cz.cuni.mff.d3s.spl.Result;
import cz.cuni.mff.d3s.spl.data.DataSource;
import cz.cuni.mff.d3s.spl.interpretation.Interpretation;

import java.util.Set;

/** SPL formula.
 * 
 * It is up to implementing classes to construct the actual formula
 * and provide the implementation how to evaluate it.
 * 
 * The expected usage is following: user creates the formula, using
 * aliases for the random variables.
 * She then binds the aliases to actual random variables.
 * Before evaluating, it is necessary to set the mathematical apparatus
 * used for evaluating.
 * The apparatus can be used to determine relation between two random variables
 * (greater/smaller, etc.).
 * The evaluate then returns result of the evaluation at the time of calling
 * the function.
 */
public interface Formula {
	
	/** Set how to evaluate statistical tests and other mathematical
	 * operations.
	 * 
	 * @param interpretation The mathematical interpretation to use.
	 */
	void setInterpretation(Interpretation interpretation);
	
	/** Bind given variable alias to a concrete data source.
	 * 
	 * This method must be called for all variables in the formula prior
	 * formula evaluation.
	 * 
	 * @param variable Variable name as used in the formula.
	 * @param data Actual data source to use (must not be null).
	 */
	void bind(String variable, DataSource data);
	
	/** Evaluate the formula.
	 * 
	 * @param significanceLevel Requested significance level of the result.
	 * @return Whether the formula evaluates to true.
	 */
	Result evaluate(double significanceLevel);

	/** Get set of variables, which needs to be bound before evaluation.
	 *
	 * @return Set of variables inside formula.
	 */
	Set getVariables();
}