analytics/math3/src/main/java/org/apache/edgent/analytics/math3/json/JsonUnivariateAggregate.java

/*
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to you under the Apache License, Version 2.0 (the
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  http://www.apache.org/licenses/LICENSE-2.0

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*/
package org.apache.edgent.analytics.math3.json;

import org.apache.edgent.function.Supplier;

/**
 * Univariate aggregate for a JSON tuple.
 * This is the declaration of the aggregate that
 * application use when declaring a org.apache.edgent.org.apache.edgent.topology.
 * <P>
 * Implementations are typically enums such
 * as {@link org.apache.edgent.analytics.math3.stat.Statistic Statistic}.
 * </P>
 * <P>
 * Each call to {@code get()} must return a new
 * {@link JsonUnivariateAggregator aggregator}
 * that implements the required aggregate.
 * </P>
 * 
 * @see JsonAnalytics
 */
public interface JsonUnivariateAggregate extends Supplier<JsonUnivariateAggregator>{
    
    /**
     * JSON key used for representation of the number
     * of tuples that were aggregated. Value is {@value}.
     */
    public static final String N = "N";
    
    /**
     * Name of the aggregate.
     * The returned value is used as the JSON key containing
     * the result of the aggregation.
     * @return Name of the aggregate.
     */
    public String name();
}