package com.tinkerpop.blueprints;
import java.util.Set;
/**
* An Element is the base class for both vertices and edges.
* An element has an identifier that must be unique to its inheriting classes (vertex or edges).
* An element can maintain a collection of key/value properties.
* Keys are always Strings and values can be any Object.
* Particular implementations can reduce the space of objects that can be used as values.
* Typically, objects are Java primitives (e.g. String, long, int, boolean, etc.)
*
* @author Marko A. Rodriguez (http://markorodriguez.com)
*/
public abstract interface Element {
/**
* Return the object value associated with the provided string key.
* If no value exists for that key, return null.
*
* @param key the key of the key/value property
* @return the object value related to the string key
*/
public <T> T getProperty(String key);
/**
* Return all the keys associated with the element.
*
* @return the set of all string keys associated with the element
*/
public Set<String> getPropertyKeys();
/**
* Assign a key/value property to the element.
* If a value already exists for this key, then the previous key/value is overwritten.
*
* @param key the string key of the property
* @param value the object value o the property
*/
public void setProperty(String key, Object value);
/**
* Un-assigns a key/value property from the element.
* The object value of the removed property is returned.
*
* @param key the key of the property to remove from the element
* @return the object value associated with that key prior to removal
*/
public <T> T removeProperty(String key);
/**
* Remove the element from the graph.
*/
public void remove();
/**
* An identifier that is unique to its inheriting class.
* All vertices of a graph must have unique identifiers.
* All edges of a graph must have unique identifiers.
*
* @return the identifier of the element
*/
public Object getId();
}