/interpreter/tags/at2dist110511/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.ATNil;
 36import edu.vub.at.objects.ATObject;
 37import edu.vub.at.objects.ATTypeTag;
 38import edu.vub.at.objects.ATTable;
 39import edu.vub.at.objects.grammar.ATSymbol;
 40
 41/**
 42 * The class ATActorMirror prescribes the minimal set of methods to be provided by the default 
 43 * implementation of an actor mirror. Since new actor mirrors can be installed dynamically, 
 44 * ATActorMirror defines the dependencies of the lexically scoped objects on the dynamic 'actor 
 45 * context' to perform their duties. The hooks defined in this class relate to:
 46 * 
 47 * <ul>
 48 *   <li>Asynchronous message creation and sending to influence the communication protocol</li>
 49 *   <li>Service advertising and requesting to influence the service discovery protocol</li>
 50 *   <li>Mirror creation to provide support for true stratification</li>
 51 *   <li>Actor protocol installation to deal with actor mirror interaction and to allow freezing
 52 *   an actor with a given protocol</li>
 53 * </ul>
 54 *
 55 * @author smostinc
 56 */
 57public interface ATActorMirror extends ATObject {
 58		
 59    /* ---------------------------------------------------
 60     * -- Language Construct to NATActorMirror Protocol --
 61     * --------------------------------------------------- */
 62
 63	/**
 64	 * Creates a first-class message in the language. Note that upon creation the
 65	 * message does not have a receiver yet. This field will be set once the message
 66	 * is actually being sent, a fact which can be intercepted by overriding the sendTo
 67	 * base-level method.
 68	 * 
 69	 * @param selector the name of the method to trigger remotely
 70	 * @param arguments the actual arguments of the message
 71	 * @param types the types with which the message will be born
 72	 */
 73	public ATAsyncMessage base_createMessage(ATSymbol selector, ATTable arguments, ATTable types) throws InterpreterException;
 74	
 75	/**
 76	 * Creates a mirror on the given object. This method serves as the 'mirror factory'
 77	 * for the current actor.
 78	 */
 79	public ATObject base_createMirror(ATObject onObject) throws InterpreterException;
 80	
 81	/**
 82	 * This method implements the default asynchronous message sending semantics for
 83	 * this particular actor. In addition to the ability to override the send meta-
 84	 * operation on a single object to have specific adaptions, this hook allows the
 85	 * programmer to modify the message sending semantics for all objects inside an 
 86	 * actor. The default implementation ensures the correct passing of messages when
 87	 * they transgress the boundaries of the sending actor. 
 88	 * 
 89	 * @throws InterpreterException
 90	 */
 91	public ATObject base_send(ATObject receiver, ATAsyncMessage message) throws InterpreterException;
 92	
 93	/**
 94	 * When an actor receives an asynchronous message for a given receiver, it will delegate this
 95	 * to the meta-level 'receive' operation of the designated object. This operation is introduced
 96	 * as a mechanism to alter the semantics of message reception for all objects contained in an
 97	 * actor. It can be used e.g. to keep track of all succesfully processed messages. 
 98	 */
 99	public ATObject base_receive(ATObject receiver, ATAsyncMessage message) throws InterpreterException;
100	
101	/**
102	 * This method provides access to a snapshot of the inbox of an actor. It is however not causally
103	 * connected to the inbox; adding/removing elements to/from this snapshot will not affect the inbox of
104	 * the actor.
105	 * @return a table containing all letters that are scheduled to be processed
106	 */
107	public ATTable base_listIncomingLetters() throws InterpreterException;
108	
109	/**
110	 * This mechanism allows for changing the scheduling semantics of the actor's inbox.
111	 * Note: this method is responsible for calling the <tt>serve()</tt> method for each
112	 * scheduled message, which should be executed at a later point in time.
113	 * 
114	 * @return a letter, which can be canceled again
115	 */
116	public ATObject base_schedule(ATObject receiver, ATAsyncMessage message) throws InterpreterException;
117	
118	/**
119	 * This method fetches and processes the next letter from the inbox.
120	 * It should take into account the possibility that the inbox is empty.
121	 */
122	public ATObject base_serve() throws InterpreterException;
123
124	/**
125	 * This method provides access to a snapshot of the current published services of an actor.
126	 * The result is not causally connected; adding/removing elements to/from this snapshot will
127	 * not affect the current publications.
128	 * @return a table containing all publications of this actor
129	 */
130	public ATTable base_listPublications() throws InterpreterException;
131
132	/**
133	 * This method provides access to a snapshot of the current subscriptions of an actor.
134	 * The result is not causally connected; adding/removing elements to/from this snapshot will
135	 * not affect the current subscriptions.
136	 * @return a table containing all subscriptions of this actor
137	 */
138	public ATTable base_listSubscriptions() throws InterpreterException;
139	
140	/**
141	 * This mechanism is the most basic mechanism to provide a service. It requires 
142	 * a separate service description and an object offering the service. The return
143	 * value is a publication object which allows cancelling the service offer.
144	 */
145	public ATObject base_provide(ATTypeTag topic, ATObject service) throws InterpreterException;
146	
147	/**
148	 * This mechanism is the most basic mechanism to require a service. The return
149	 * value is a subscription object which allows cancelling the service offer.
150	 * @param bool - if true, the subscription is permanent, if false, once the subscription
151	 * has been satisfied, it is automatically cancelled.
152	 */
153	public ATObject base_require(ATTypeTag topic, ATClosure handler, ATBoolean bool) throws InterpreterException;
154	
155	/**
156	 * Create a far reference to a local object. Custom actor mirrors may override
157	 * this method in order to return different kinds of object references, e.g.
158	 * leased object references.
159	 * 
160	 * @param toObject a **near** reference to the object to export
161	 * @return a local far reference to the object being exported
162	 * @throws XIllegalOperation if the passed object is a far reference, i.e. non-local
163	 */
164	public ATObject base_createReference(ATObject toObject) throws InterpreterException;
165	
166	/**
167	 * def oldprotocol := actor.becomeMirroredBy: newprotocol
168	 * 
169	 * Installs a new meta-object protocol into this actor.
170	 * 
171	 * @param protocol meta-level code that overrides an actor's MOP methods
172	 * @return the previously installed meta-object protocol
173	 */
174	public ATObject base_becomeMirroredBy_(ATActorMirror protocol) throws InterpreterException;
175	
176	/**
177	 * def aM := implicitActorMirror.getExplicitActorMirror()
178	 * 
179	 * This method serves as the 'mirror factory' for explicit actor mirrors.
180	 * 
181	 * @return an explicit actor mirror for the current actor.
182	 */
183	public ATActorMirror base_getExplicitActorMirror() throws InterpreterException;
184	
185	/**
186	 * Provides access to this actor's "behaviour" object. This is the first
187	 * object created within an actor.
188	 * 
189	 * Note: if the behaviour is accessed when evaluating the "init.at" initialization
190	 * file of an actor, the behaviour will <em>not have been initialized</em> yet.
191	 * It will appear as an empty object.
192	 */
193	public ATObject base_behaviour() throws InterpreterException;
194	
195    /* -------------------------------------
196     * -- Object Passing Protocol Support --
197     * ------------------------------------- */
198
199	/**
200	 * This mechanism interacts with the built-in receptionists set of the actor to 
201	 * produce a new far object reference to a local object. The created far object
202	 * is by no means unique within the actor that created it. 
203	 * 
204	 * Creating such far references is performed when passing objects by reference
205	 * in the meta_pass method of scoped objects such as closures, objects and fields.
206	 * 
207	 * @param object the local object to be given a reference to
208	 * @return a newly created far object reference
209	 * 
210	 * @see edu.vub.at.objects.ATObject#meta_pass(ATFarReference)
211	 */
212	//public ATFarReference base_export(ATObject object) throws InterpreterException;
213	
214	/**
215	 * This mechanism interacts with the built-in receptionists set of the actor to 
216	 * resolve far references (which were received as part of an async message). The
217	 * method returns a local object whenever the far object denotes an object 
218	 * hosted by this actor. 
219	 * 
220	 * If the denoted object is not hosted by this actor, a far object (possibly but
221	 * not necessarily the passed one) is returned which is the local and unique 
222	 * representative of the remote object. This object will contain the queue of 
223	 * messages to be transmitted to the remote object. 
224	 * 
225	 * @param farReference the far reference to be resolved
226	 * @return a local object | a unique far reference for this actor
227	 */
228	//public ATObject base_resolve(ATFarReference farReference) throws InterpreterException;
229
230}