Persistence unified - Revision history

Marco Piccioni: /* Design principles */

2009-04-23T15:09:02Z

‎Design principles

Marco Piccioni: /* Object versioning */

2009-04-23T15:08:16Z

‎Object versioning

Marco Piccioni: /* Design orthogonality */

2009-04-23T14:57:02Z

‎Design orthogonality

Marco Piccioni: /* Object versioning */

2007-08-30T14:28:48Z

‎Object versioning

Marco Piccioni: /* Extendibility */

2007-08-30T14:28:28Z

‎Extendibility

Marco Piccioni: /* Design orthogonality */

2007-08-30T14:27:40Z

‎Design orthogonality

Marco Piccioni: /* Persistence uniformity */

2007-08-30T14:26:03Z

‎Persistence uniformity

Bertrand Meyer at 00:32, 27 August 2007

2007-08-27T00:32:47Z

Bertrand Meyer: /* Design orthogonality */

2007-08-27T00:11:18Z

‎Design orthogonality

Bertrand Meyer at 00:11, 27 August 2007

2007-08-27T00:11:01Z

@@ Line 21: / Line 21: @@
 # Encapsulation and extension
 # Pure Eiffel
-# Object versioning
+# Object and class versioning
 # Newbie-proof

@@ Line 39: / Line 39: @@
 (Handles to existing C-based mechanisms, e.g. a relational DBMS, may as usual require short C routines.)
-===Object versioning===
+===Object and class versioning===
-PERSIST should make it possible to retrieve objects even if the class description has changed. Conversions should be safe; developers should be given the choice of how much control they exert over them.
+PERSIST should make it possible to retrieve objects even if the class description has changed. Conversions between objects of different versions should be safe. All the different class versions should be stored in a central repository, together with the appropriate conversion routines.
 ===Newbie-proof===

@@ Line 26: / Line 26: @@
 ===Design orthogonality===
-It should be possible to add persistence mechanisms to an application without affecting the other aspects of its design. For example, developers should not need to add persistence-related attributes, or require application classes to inherit from specific persistence classes.
+It should be possible to add persistence mechanisms to an application without affecting the other aspects of its design. For example, developers should not need to add persistence-related attributes to application classes, or require them to inherit from specific persistence classes.
 ===Persistence uniformity===

@@ Line 39: / Line 39: @@
 (Handles to existing C-based mechanisms, e.g. a relational DBMS, may as usual require short C routines.)
-==Object versioning==
+===Object versioning===
 PERSIST should make it possible to retrieve objects even if the class description has changed. Conversions should be safe; developers should be given the choice of how much control they exert over them.
 ===Newbie-proof===
 This is a direct application of the above requirement of simplicity: it should be possible for a novice programmer to store an object or an object structure using a straightforward single instruction, similar to what STORABLE permits today.
 ==Initial design==

@@ Line 31: / Line 31: @@
 There are many kinds of persistence media, from plain files to relational databases, object-oriented databases and networks. Programmers using PERSIST should only have to take into account the properties of the persistence medium that they choose to consider. This means in particular that it must be possible to write a PERSIST application that will work with different persistence media.
-===Extendibility===
+===Encapsulation and Extension===
 It should be possible to add new kinds of persistence medium. For a possible approach see XXX_FORMAT classes below.

@@ Line 15: / Line 15: @@
 ==Design principles==
-The first task is to agree on desirable features for PERSIST. Here is a first proposal:
+The following goals, detailed next, appear essential:
 # Design orthogonality
@@ Line 21: / Line 21: @@
 # Encapsulation and extension
 # Pure Eiffel
 # Newbie-proof
 ===Design orthogonality===
@@ Line 30: / Line 29: @@
 ===Persistence uniformity===
 There are many kinds of persistence medium, from plain files to relational databases, object-oriented databases and networks. Programmers using PERSIST should only have to take into account the properties of the persistence medium that they choose to consider. This means in particular that it must be possible to write a PERSIST application that will work with different persistence media.
 ===Extendibility===
-It should be possible to add new kinds of persistence medium. (For a possible approach see XXX_FORMAT classes below.)
+It should be possible to add new kinds of persistence medium. For a possible approach see XXX_FORMAT classes below.
 ===Pure Eiffel===
-No external calls to C macros, just plain Eiffel should be used to implement the framework
+PERSIST should entirely be implementable in Eiffel: no C routines or macros.
 ===Newbie-proof===
-Ideally the programmer should only create the desired manager object and invoke the features to store or retrieve an object  passing the object itself as an argument.
+This is a direct application of the above requirement of simplicity: it should be possible for a novice programmer to store an object or an object structure using a straightforward single instruction, similar to what STORABLE permits today.
 ===Essential abstractions===
-It should be possible to develop most persistence-aware applications based on knowledge of just three abstractions:
+We have produced a first design intended to satisfy the above criteria.
 *PERSISTENCE_MEDIUM, covering the kind of medium onto which objects are mapped; it should be possible to work with a very abstract view of such a medium, or, if desired, to take advantage of more specific properties.
 *PERSISTENCE_FORMAT, controlling the mapping between object properties and their outside representation.
 *PERSISTENCE_MANAGER: control object to specify modalities of writing and reading, and find out how the operations actually occurred.
-Possible specializations of these abstractions could be:
+Possible specializations of these abstractions include:
 * FILE_MEDIUM, NETWORK_MEDIUM, RELATIONAL_DB_MEDIUM, CUSTOM_MEDIUM, ...
@@ Line 56: / Line 65: @@
 * BINARY_SERIALIZATION_MANAGER, RDBMS_MANAGER, CUSTOM_MANAGER, ...
-==Diagrams and code samples==
+==Discussion==
-Here is a link to the [[persistence code samples]] page where you can have a look at some code and a class diagram.
+Feel free to participate in the [[persistence framework design discussion]].
-==Open discussion==
+===Name search===
-For an open discussion on the design choices please have a look at the [[persistence framework design discussion]].
+PERSIST is a placeholder name. Suggestions are welcome.
-==Additional tasks==
-===Which name?===
-Find an appropriate name for the framework is, of course, absolutely fundamental. It seems fair that anyone interested could provide one or more names within a certain period of time. After that a poll may be created to determine the winner. A first proposal could be EIUNPE which stands for EIffel UNified PErsistence.
 ==Contacts==
 *Marco Piccioni
 *Bertrand Meyer