--- Release version 1.01 21.22.2003 -------------------------------------
Initial release

--- Release version 1.02 25.02.2003 -------------------------------------
1. Support value types
2. Add FieldIndex interface
3. Fix bug in unique index support

--- Release version 1.03 03.03.2003 -------------------------------------
1. Fix bug in LinkImpl constructor
2. Make it possible to call IPersistent.deallocate multiple times.

--- Release version 1.04 12.03.2003 -------------------------------------
1. Fix bug in rollback method
2. Add IPersistent.onLoad method
3. Fix bugs in BtreeFieldIndex
4. Add TestLink example

--- Release version 1.05 04.04.2003 -------------------------------------
1. Add optional garbage collection

--- Release version 1.06 09.04.2003 -------------------------------------
1. Add obejct level locking

--- Release version 1.07 18.04.2003 -------------------------------------
1. Add Persistent.modify method, allowing to mark object as dirty. 
Object will be automatically saved during transaction commit.
2. Add index iterator.
3. Add spatial index.


--- Release version 1.08 22.04.2003 -------------------------------------
1. Implement more sophisticated iterators for index search  
2. Fix bug in R-Tree
 
--- Release version 1.09 06.05.2003 -------------------------------------
1. Fix bug in packing array of strings. 

--- Release version 1.10 28.05.2003 -------------------------------------
1. Add Storage.isOpened() method
2. Change store() with modify() in Btree implementation

--- Release version 1.11 09.06.2003 -------------------------------------
1. Add methods for database import/export in XML format. 

--- Release version 1.12 18.06.2003 -------------------------------------
1. Fix bug in Btree (replacing existed values in scalar index)
2. Using CSharp serialization mechanism to store in database alien objects

--- Release version 1.13 04.07.2003 -------------------------------------
1. Make it possible to provide user specific implementation of PERST file interface. 
For example it can be used to work with flash card or encrypted files.

--- Release version 1.14 09.07.2003 -------------------------------------
1. Add Storage.getObjectByOID method
2. Add autoincremented field support: FieldIndex.append method

--- Release version 1.15 16.07.2003 -------------------------------------

1. Add Index.GetDicitionaryEnumerator() method which makes it possible to access both key and value.

--- Release version 1.16 23.07.2003 -------------------------------------

1. Fix bug in index iterator (iterating through empty index)

--- Release version 1.17 01.08.2003 -------------------------------------

1. Store weak references in modified object list to make it possible to GC to reclaim these objects
2. Support sets of persistent objects (Storage.createSet method)

--- Release version 1.18 19.09.2003 -------------------------------------

1. Add enumeration and indexation methods to Link interface. 

--- Release version 1.19 24.09.2003 -------------------------------------

1. Provide new implementation of modified object list. Old implementation introduced in 
version 1.17 and based on weak reference in finalize method in Persistent class
can cause loose of modifications if weak reference is cleared by GC, but finalize
method is not invoked before transaction commit.

--- Release version 1.20 02.10.2003 -------------------------------------

1. Add FieldIndex.contains method
2. Port to Visual Studio 2003
3. Support of Compact .Net framework
4. Conditional compilation of code supporting raw binary type
(System.Runtime.Serialization.Formatters.Binary.BinaryFormatter class in not supported in Compact.Net framework)
5. Replace '+' in C# identifiers during XML export

--- Release version 1.21 08.10.2003 -------------------------------------

1. Support of main-memory databases. 

--- Release version 1.22 17.10.2003 -------------------------------------

1. Add SortedCollection container class
2. Fix bugs in main-memory database support
3. Fix bug with lost modifications

--- Release version 2.01 23.10.2003 -------------------------------------

1. Automatic scheme evaluation support.
Attention: database format is incompatible with version 1.22!
2. New implementation of modified object list
3. Make it possible to tune most of database parameters using Storage.setProperty/Storage.setProperties methods


--- Release version 2.02 07.11.2003 -------------------------------------

1. Support indices for byte arrays
2. Support compound indices
3. Fix bug un unpacking arrays of enums.

--- Release version 2.03 19.11.2003 -------------------------------------

1. Add IPersistent.invalidate method. Transaction rollback will now invalidate all modified objects.
2. Support per-thread transactions (Storage.beginTransaction and Storage.endTranasction methods)
3. Yet another attempt to eliminate modification list and handle modified object using weak references.
4. Rename all public Perst methods according to C# naming convention.

--- Release version 2.04 26.11.2003 -------------------------------------
1. Derive ISet from IPersistent and IResource interfaces

--- Release version 2.05 28.11.2003 -------------------------------------

1. Make it possible to profile storage memory using Storage.getMemoryDump() method 

--- Release version 2.06 11.12.2003 -------------------------------------

1. Make it possible to index properties
2. Fix bug in packing char fields.
3. Support of decimal and Guid types

--- Release version 2.07 14.12.2003 -------------------------------------

1. Fix critical bug in object index relocation algorithm
2. Fix bug in recovery procedure

--- Release version 2.08 20.12.2003 -------------------------------------

1. Add Blob class

--- Release version 2.09 23.12.2003 -------------------------------------
1. Fix bug in Link.insert method
2. Add ClassLoader interface and Storage.Loader property

--- Release version 2.10 30.12.2003 -------------------------------------
1. Fix bug in XML import

--- Release version 2.11 07.01.2004 -------------------------------------
1. Add Storage.backup method which can be used for online backups and database compactification
2. Add support of time series
3. Fix bugs in unpacking arrays of values

--- Release version 2.12 12.01.2004 -------------------------------------
1. Dynamically generate packing/unpacking code for persistent objects. 
This feature works only for public classes with public members
and not having components of the following types: value, 
array of value, array of objects, arrays of enums.
Also it is not supported in Compact.NET version. 
Dynamic generation is automatically used when class meets described
above criteria.


--- Release version 2.13 24.01.2004 -------------------------------------
1. Fix bugs in dynamic packing/unpacking code generation algorithm
2. Support persistency for MarshalByRef objects (add MarshalByRefPersistent class)

--- Release version 2.14 30.01.2004 -------------------------------------
1. Fix bug in Guid pack method
2. Fix bug in object modification mechanism which can cause deadlock.
3. Make it possible to specify part of compound key in query

--- Release version 2.15 06.02.2004 -------------------------------------
1. Fix bugs with unpacking fields of byte, sbyte, ushort and uint types.

--- Release version 2.16 10.02.2004 -------------------------------------
1. Fix bug in Persistent.invalidate method

--- Release version 2.17 26.02.2004 -------------------------------------
1. Fix bug in code checking when pack/unpack method generation is possible
2. Add check for concurrent modifications in B-Tree iterator
3. Add Projection class
4. Add Index.getPrefix, Index.prefixIterator, FieldIndex.getPrefix and FieldIndex.prefixIterator methods
5. Fix bugs in RelationImpl class

--- Release version 2.18 07.03.2004 -------------------------------------
1. Add default comparer for SortedCollection class (expecting that members of collection 
   implement Comparable interface)
2. Fix bug in Index.Set method for non-unique indices
3. Support of database file encryption 

--- Release version 2.19 18.03.2004 -------------------------------------
1. Fix bug in file encyption
2. Optimize class lookup algorithm
3. Add perst.code.generation property which allows to enable or disable dynamic generation
of pack/unpack methods.
4. Generation of pack/unpack methods in background (by separate thread)

--- Release version 2.20 04.04.2004 -------------------------------------
1. Add Link.Pin and Link.Unpin methods. Do not implicitely pin accessed Link elements.
2. Change class descriptor loading algorithm to avoid stack overflow
   in applications with large number of classes
3. Detect bugs related with incorrect serialization of persistent object as raw or value type
4. Fix bug in automatic scheme evalaution implementation.

--- Release version 2.21 16.04.2004 -------------------------------------
1. Add Index.KeyType, FieldIndex.IndexedClass and FieldIndex.KeyFields properties
2. Add Index.PrefixSearch method which can be used to locate keys which are prefixes of the specified word.

--- Release version 2.22 10.04.2004 -------------------------------------
1. Fix bug in dbTimeSeries class
2. Implement reallocatable bitmap (now database size is not limited by dbDatabaseOffsetBits constant)

--- Release version 2.23 09.05.2004 -------------------------------------
1. Make StorageImpl.swizzle and StorageImpl.unswizzle method protected to be allow
their redefinition in derived class.
2. Fix problem with parsing ulong literals in XMLImport

--- Release version 2.24 17.05.2004 -------------------------------------
1. Index.Remove(Key), Index.Set(Key,IPersistent), FieldIndex.Remove(Key) and FieldIndex.Set(IPersistent)
methods now return reference to the removed/replaced object.

--- Release version 2.25 28.05.2004 -------------------------------------
1. Optimized version of T-Tree algorithm

--- Release version 2.26 07.06.2004 -------------------------------------
1. Fix bug in FieldIndex.remove(Key) introduced in version 2.24

--- Release version 2.27 15.06.2004 -------------------------------------
1. Add handling of Decimal and Guid types to Btree.getKeyFromObject() method 
2. Fix bug in XMLExporter.exportBinary
3. Change R-Tree and rectangle implementation to calculate rectangles area using long type

--- Release version 2.28 28.06.2004 -------------------------------------
1. Add PersistentContext and TransparentPersistenceAttrribute classes to provide
transparent persistence for C# objects using .Net remoting API. If application
class is derived from PersistentContext and marked with TransparentPersistence attribute, 
it will automatically load on demand its content from the database and automatically store
content if the object is modified. But remoting API can handle only public members of the class
and also cause significant performance overhead (invocation of method through remoting API
is about 100 times slower than normal method invocation)

--- Release version 2.29 05.07.2004 -------------------------------------
1. Make it possible to use Storage.Gc() for verification of consistency of database.
Now this method returns number of deallocated (garbage objects) and detects dangling references in
the database. 
2. Add SpatialIndexR2 and RectangleR2 classes for spatial objects with floating point coordinates.
Also new spatial index is more efficient for large collections (it doesn't pin all its pages in memory).
SpatialIndexR2 class provides iterator to accessed overlaped object one-by-one.
3. Add SpatialIndex.WrappingRectangle and  SpatialIndexR2.WrappingRectangle properties
4. Add set method to Link.Length property.

--- Release version 2.30 15.07.2004 -------------------------------------
1. Invoke Win32 FlushFileBuffers in addition to System.FileStream.Flush to 
really flush changes to the disk. 
2. Port to Mono compiler

--- Release version 2.31 06.08.2004 -------------------------------------
1. Add L2List and L2ListElem classes
2. Fix bug in importing/exporting of raw fields introduced in version 2.23
3. Fix critical sycnhronization bug in writing modified objects to the disk

--- Release version 2.32 21.08.2004 -------------------------------------
1. Fix critical synchronization bug in writing modified objects to the disk
2. Support new kind of per-thread transactions: serializable transactions
3. Alternative B-Tree implementation (as normal C# object and not using direct access 
   database pages). New implementation of B-Tree will be used instead of old implementation
   if "perst.alternative.btree" property is set. New B-Tree has incompatible format with 
   old B-Tree, so you could not use old database or XML export file with new indices. 
   Alternative B-Tree is needed to provide serializable transaction (old one could not be used).
   Also it provides better performance (about 3 times comaring with old implementation) because
   of object caching. And B-Tree supports keys of user defined types. 
4. Fix bug in Index.set method
5. Fix bug in packing array of string
6. Fields of System.Object type are now serialized decpite to whether 
   "perst.serialize.transient.objects" property was set or not
7. Add Persistent OnStore method which is invoked before object is stored in the database

--- Release version 2.33 27.08.2004 -------------------------------------
1. Background garbage collection
2. Add Storage.UsedSize and Storage.DatabaseSize properties

--- Release version 2.34 16.09.2004 -------------------------------------
1. Add "perst.file.noflush" property. When it is assigne true value, 
Perst will not perform flush of file during transaction commit. It will greatly increase performance because
eliminate synchronous write to the disk (when program has to wait until all changed
are actually written to the disk). But it can cause database corruption in case of 
OS or power failure (but abnormal termination of application itself should not cause
the problem, because all data which were written to the file, but is not yet saved to the disk is 
stored in OS file buffers and sooner or later them will be written to the disk)
2. Fix possible problems with GC memory consistency verification for T-Tree and R-Tree classes


--- Release version 2.35 02.10.2004 -------------------------------------
1. Fix problem with supporting compund keys in alternative implementation of B-Tree
2. Fix bug (cuase inefficient execution) in TimeSeries.Contains method.

--- Release version 2.36 07.10.2004 -------------------------------------
1. Make it possible to specify encoding for storing string
2. Add StorageListener class
3. Fix compilation problem with Compact.Net framework and multifield alternative indices

--- Release version 2.37 10.10.2004 -------------------------------------
1. Add PATRICIA Trie container
2. Fix problem with generated pack/unpack functions introduced in 2.36 version

--- Release version 2.38 29.10.2004 -------------------------------------
1. Fix bugs in XML import/export
2. Fix check for invalid OID in Storage.getPos method 
3. Change BLOB implementation to support work with very large BLOBs 
(done by Mikhail Kotelnikov <mikhail@kotelnikov.com>)
4. Fix bug with restoring autoincrement counter in XML import
5. Add TimeSeries.Deallocate wethod
6. Fix bug in backup with compactification (incorrect setting of bitmap end)

--- Release version 2.39 14.11.2004 -------------------------------------
1. Fix problems with handling weak references and finalization
2. Replace elements of Link with stubs after storing Link in the database
   to avoid memory overflow caused by pinning objects in memory.
3. Stop pack/unpack code generation thread in Storage.Close method
4. Add Ttree.Deallocate method
5. Support per-thread transactions for Compact.Net framework

--- Release version 2.40 16.11.2004 -------------------------------------
1. Add LRU object cache. Make it possible for user to selcet between "weak", "soft" and "lru"
   cache implementation.
2. Add PersistentString class to be able to store string in the database as independent object.
3. Fix bug in Persistent.assignOid method introduced in version 2.39
4. Fix bug in Link.indexOf method introduced in version 2.39
5. Fix synchronization problem (deadlock) in background GC activation

--- Release version 2.41 28.11.2004 -------------------------------------
1. Fix bug in comparison of int keys in multifield index
2. Fix problems with supporting more than 2^28 objects

--- Release version 2.42 06.12.2004 -------------------------------------
1. Fix bug in range search implementation in T-Tree (SortedCollection)
2. Make it possible to specify different range types (inclusive/exclusive) in SortedCollection search methods

--- Release version 2.43 10.12.2004 -------------------------------------
1. Add BitIndex collection (allowing to select object by bit vector of boolean properties)

--- Release version 2.44 14.12.2004 -------------------------------------
1. Implement yet another transparent API to the database based on virtual properties.
Now it is possible to transparently load and modify persistent objects
by accessing persistent object components through virtual properties. 
It is not needed any more to explicitly invoke IPersistent.Modify method
or redefine IPersistent.RecursiveLoading method. You only need to replace 
components of your objects with definition of abstract properties. 
Perst will automatically generate class which will provide implementations
of these properties. You only have to use IStorage.CreateClass method to construct objects
instead of direct invocation of constructors. See "PropGuess" sample.
2. Add file locking to prevent modification of database file by more than one application

--- Release version 2.45 16.12.2004 -------------------------------------
1. Derive Index and FieldIndex interface from common base GenericIndex
2. Add StreamFile 
3. Make it possible to toggle "perst.file.noflush" property on the fly (not only before storage open).
4. Fix bugs in virtual property based transparent API implementation
5. Add PArray class to be used instead of array of references in virtual property based transparent API
6. Change semantic of IPersistent.MakePersistent method, now it doesn't store transparent object
in the storage, it just assigns OID and marks it as modified

--- Release version 2.46 19.12.2004 -------------------------------------
1. Add Storage.createThickIndex method for efficient support of indices with a lot of duplicate 
   values of of the key
2. Add Storage.createScalableSet method for efficient (space and speed) support of set of references 
   small as well as large number of members
3. Fix bugs in virtual proxy transparent API implementation

--- Release version 2.47 28.12.2004 -------------------------------------
1. Support C# 2.0 generics. When Perst.NET is build with USE_GENERICS defined, 
all Perst collections will be provided as parameterized classes implementing
System.Collections.Generic.ICollection<T>

--- Release version 2.48 03.01.2005 -------------------------------------
1. Replication support. Now Perst supports master-slaves replication model.
Single master node replicates changes to one or more slave nodes.
It is possible to access database at slave nodes in read-only mode.
Look at TestReplic example.

--- Release version 2.49 09.01.2005 -------------------------------------
1. Change implementation of Link to automatically set modified bit in contaning object.
Now it is not necessary to explicitly call modify() for object which Link component is updated.

--- Release version 2.50 25.02.2005 -------------------------------------
1. Change Perst license. Starting from this version Perst it is necessary to buy 
commercial license for using Perst in commercial products. 
2. Fix race condition problem in Persistent.load method

--- Release version 2.51 07.02.2005 -------------------------------------
1. Integrate JSQL - make it possible to select collection members using SQL-like queries
2. Fix bug in fetching classes with privite fields declared in base classes

--- Release version 2.52 11.02.2005 -------------------------------------
1. Add Database class emulating object-relational database on top of Perst

--- Release version 2.53 22.02.2005 -------------------------------------
1. Support concurrent iterators (recover iterator state instead of throwing 
   ConcurrentModificationException if underlying collection is modified outside iterator)
2. Support generics for the latest release of Visual Studion 2005.

--- Release version 2.54 2.03.2005 -------------------------------------
1. Fix bugs in AltBtree iterators introduced in 2.53 version

--- Release version 2.55 21.03.2005 -------------------------------------
1. Add versioning support (Version and VersionHistory classes)
2. Avoid false ambiguity exceptions if same assembly is specified twice in assembly list

--- Release version 2.56 19.05.2005 -------------------------------------
1. Add "perst.slave.connection.timeout" storage property allowing to specify connection timeout for
   replicated model.
2. Do not insert entries in object cache during finalization
   
--- Release version 2.57 08.06.2005 -------------------------------------
1. Add Storage.merge(Iterator[]) and Storage.join(Iterator[]) to efficiently merge and join 
   results of several index searches. It allows efficient implementation of complex search conditions.
2. Force assignment of OID to objects referenced by fields used as a key in FieldIndex 
   when object is inserted in index. 
3. Fix problem with interference of explicit deallocation of objects and garbage collection

--- Release version 2.58 19.06.2005 -------------------------------------
1. Support compound indices (before Perst supports only compound multi-field indices)
2. Support RDF data model (http://www.w3.org/RDF/): store/fetch/searching RDF data, XML based queries
3. Change Database class to support table inheritance and polymorphic queries.