/interpreter/tags/reactive-pattern-matching/src/edu/vub/at/actors/ATActorMirror.java

  1/**
  2 * AmbientTalk/2 Project
  3 * ATActorMirror.java created on Aug 21, 2006
  4 * (c) Programming Technology Lab, 2006 - 2007
  5 * Authors: Tom Van Cutsem & Stijn Mostinckx
  6 * 
  7 * Permission is hereby granted, free of charge, to any person
  8 * obtaining a copy of this software and associated documentation
  9 * files (the "Software"), to deal in the Software without
 10 * restriction, including without limitation the rights to use,
 11 * copy, modify, merge, publish, distribute, sublicense, and/or
 12 * sell copies of the Software, and to permit persons to whom the
 13 * Software is furnished to do so, subject to the following
 14 * conditions:
 15 *
 16 * The above copyright notice and this permission notice shall be
 17 * included in all copies or substantial portions of the Software.
 18 *
 19 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 20 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
 21 * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 22 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
 23 * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
 24 * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 25 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 26 * OTHER DEALINGS IN THE SOFTWARE.
 27 */
 28
 29package edu.vub.at.actors;
 30
 31import edu.vub.at.exceptions.InterpreterException;
 32import edu.vub.at.exceptions.XIllegalOperation;
 33import edu.vub.at.objects.ATBoolean;
 34import edu.vub.at.objects.ATClosure;
 35import edu.vub.at.objects.ATObject;
 36import edu.vub.at.objects.ATTable;
 37import edu.vub.at.objects.ATTypeTag;
 38import edu.vub.at.objects.grammar.ATSymbol;
 39
 40/**
 41 * The class ATActorMirror prescribes the minimal set of methods to be provided by the default 
 42 * implementation of an actor mirror. Since new actor mirrors can be installed dynamically, 
 43 * ATActorMirror defines the dependencies of the lexically scoped objects on the dynamic 'actor 
 44 * context' to perform their duties. The hooks defined in this class relate to:
 45 * 
 46 * <ul>
 47 *   <li>Asynchronous message creation and sending to influence the communication protocol</li>
 48 *   <li>Service advertising and requesting to influence the service discovery protocol</li>
 49 *   <li>Mirror creation to provide support for true stratification</li>
 50 *   <li>Actor protocol installation to deal with actor mirror interaction and to allow freezing
 51 *   an actor with a given protocol</li>
 52 * </ul>
 53 *
 54 * @author smostinc
 55 */
 56public interface ATActorMirror extends ATObject {
 57		
 58    /* ---------------------------------------------------
 59     * -- Language Construct to NATActorMirror Protocol --
 60     * --------------------------------------------------- */
 61
 62	/**
 63	 * Creates a first-class message in the language. Note that upon creation the
 64	 * message does not have a receiver yet. This field will be set once the message
 65	 * is actually being sent, a fact which can be intercepted by overriding the sendTo
 66	 * base-level method.
 67	 * 
 68	 * @param selector the name of the method to trigger remotely
 69	 * @param arguments the actual arguments of the message
 70	 * @param types the types with which the message will be born
 71	 */
 72	public ATAsyncMessage base_createMessage(ATSymbol selector, ATTable arguments, ATTable types) throws InterpreterException;
 73	
 74	/**
 75	 * Creates a mirror on the given object. This method serves as the 'mirror factory'
 76	 * for the current actor.
 77	 */
 78	public ATObject base_createMirror(ATObject onObject) throws InterpreterException;
 79	
 80	/**
 81	 * This method implements the default asynchronous message sending semantics for
 82	 * this particular actor. In addition to the ability to override the send meta-
 83	 * operation on a single object to have specific adaptions, this hook allows the
 84	 * programmer to modify the message sending semantics for all objects inside an 
 85	 * actor. The default implementation ensures the correct passing of messages when
 86	 * they transgress the boundaries of the sending actor. 
 87	 * 
 88	 * @throws InterpreterException
 89	 */
 90	public ATObject base_send(ATObject receiver, ATAsyncMessage message) throws InterpreterException;
 91	
 92	/**
 93	 * When an actor receives an asynchronous message for a given receiver, it will delegate this
 94	 * to the meta-level 'receive' operation of the designated object. This operation is introduced
 95	 * as a mechanism to alter the semantics of message reception for all objects contained in an
 96	 * actor. It can be used e.g. to keep track of all succesfully processed messages. 
 97	 */
 98	public ATObject base_receive(ATObject receiver, ATAsyncMessage message) throws InterpreterException;
 99	
100	/**
101	 * This method provides access to a snapshot of the inbox of an actor. It is however not causally
102	 * connected to the inbox; adding/removing elements to/from this snapshot will not affect the inbox of
103	 * the actor.
104	 * @return a table containing all letters that are scheduled to be processed
105	 */
106	public ATTable base_listIncomingLetters() throws InterpreterException;
107	
108	/**
109	 * This mechanism allows for changing the scheduling semantics of the actor's inbox.
110	 * @return a letter, which can be canceled again
111	 */
112	public ATObject base_schedule(ATObject receiver, ATAsyncMessage message) throws InterpreterException;
113	
114	/**
115	 * This method fetches and processes the next letter from the inbox.
116	 * It should take into account the possibility that the inbox is empty.
117	 */
118	public ATObject base_serve() throws InterpreterException;
119
120	/**
121	 * This method provides access to a snapshot of the current published services of an actor.
122	 * The result is not causally connected; adding/removing elements to/from this snapshot will
123	 * not affect the current publications.
124	 * @return a table containing all publications of this actor
125	 */
126	public ATTable base_listPublications() throws InterpreterException;
127
128	/**
129	 * This method provides access to a snapshot of the current subscriptions of an actor.
130	 * The result is not causally connected; adding/removing elements to/from this snapshot will
131	 * not affect the current subscriptions.
132	 * @return a table containing all subscriptions of this actor
133	 */
134	public ATTable base_listSubscriptions() throws InterpreterException;
135	
136	/**
137	 * This mechanism is the most basic mechanism to provide a service. It requires 
138	 * a separate service description and an object offering the service. The return
139	 * value is a publication object which allows cancelling the service offer.
140	 */
141	public ATObject base_provide(ATTypeTag topic, ATObject service) throws InterpreterException;
142	
143	/**
144	 * This mechanism is the most basic mechanism to require a service. The return
145	 * value is a subscription object which allows cancelling the service offer.
146	 * @param bool - if true, the subscription is permanent, if false, once the subscription
147	 * has been satisfied, it is automatically cancelled.
148	 */
149	public ATObject base_require(ATTypeTag topic, ATClosure handler, ATBoolean bool) throws InterpreterException;
150	
151	/**
152	 * Create a far reference to a local object. Custom actor mirrors may override
153	 * this method in order to return different kinds of object references, e.g.
154	 * leased object references.
155	 * 
156	 * @param toObject a **near** reference to the object to export
157	 * @return a local far reference to the object being exported
158	 * @throws XIllegalOperation if the passed object is a far reference, i.e. non-local
159	 */
160	public ATObject base_createReference(ATObject toObject) throws InterpreterException;
161	
162	/**
163	 * def oldprotocol := actor.becomeMirroredBy: newprotocol
164	 * 
165	 * Installs a new meta-object protocol into this actor.
166	 * 
167	 * @param protocol meta-level code that overrides an actor's MOP methods
168	 * @return the previously installed meta-object protocol
169	 */
170	public ATObject base_becomeMirroredBy_(ATActorMirror protocol) throws InterpreterException;
171	
172	/**
173	 * def aM := implicitActorMirror.getExplicitActorMirror()
174	 * 
175	 * This method serves as the 'mirror factory' for explicit actor mirrors.
176	 * 
177	 * @return an explicit actor mirror for the current actor.
178	 */
179	public ATActorMirror base_getExplicitActorMirror() throws InterpreterException;
180	
181    /* -------------------------------------
182     * -- Object Passing Protocol Support --
183     * ------------------------------------- */
184
185	/**
186	 * This mechanism interacts with the built-in receptionists set of the actor to 
187	 * produce a new far object reference to a local object. The created far object
188	 * is by no means unique within the actor that created it. 
189	 * 
190	 * Creating such far references is performed when passing objects by reference
191	 * in the meta_pass method of scoped objects such as closures, objects and fields.
192	 * 
193	 * @param object the local object to be given a reference to
194	 * @return a newly created far object reference
195	 * 
196	 * @see edu.vub.at.objects.ATObject#meta_pass(ATFarReference)
197	 */
198	//public ATFarReference base_export(ATObject object) throws InterpreterException;
199	
200	/**
201	 * This mechanism interacts with the built-in receptionists set of the actor to 
202	 * resolve far references (which were received as part of an async message). The
203	 * method returns a local object whenever the far object denotes an object 
204	 * hosted by this actor. 
205	 * 
206	 * If the denoted object is not hosted by this actor, a far object (possibly but
207	 * not necessarily the passed one) is returned which is the local and unique 
208	 * representative of the remote object. This object will contain the queue of 
209	 * messages to be transmitted to the remote object. 
210	 * 
211	 * @param farReference the far reference to be resolved
212	 * @return a local object | a unique far reference for this actor
213	 */
214	//public ATObject base_resolve(ATFarReference farReference) throws InterpreterException;
215
216}