Persistence for the xmlBlaster

[manuel Kron <manuel.kron at gmx.net>]

Hi,

i will programming a persistence DOM (PDOM) with XPATH-engine.
for the xmlBlaster.

The PDOM based on a direct-mapped-cache with write-trougth
Cache-strategie. The direct-mapped-policy is very easy.

Basics
-----
1. All DOM-Node of the xmlBlaster are divided in fix pages.
    e.g. 128 Nodes -> 1. Page
           256 Nodes -> 2. Page

     ---------
     |   Page 1     |
     ---------
     |  Page  2     |
     ---------
     |  Page  N    |
     ---------

2. Caching

The cache has a fixed memory size (e.g. 4 MB DOM-Nodes). Each
cacheline consists of  next format :

 ------------------------------------------------
 |      Tag                                | V | M | LRU |     4
DOM-Node            |
 ------------------------------------------------

Tag = directory the DOM-Nodes
V     = Vaild-Bit
M     = Modify-Bit
LRU = least recently used DOM-Node

Each DOM-Node-address of the xmlBlaster is mapped  to a virtuell-
file-address on the harddisc-memory. A harddisc-memory-page is a file
now.

E.g. :
---

DOM-Tree   (in the brackets = address of each Node)
--------

  /Root
  |
  --/ A   (1)
       |
       |--/AA (2)
       |
       --/AB  (3)


Access on the cache over a virtuell adress
-------------------------------

  -------------------------------
  |   Tag      |  Block-Nr.    | Index  |  Node-Nr. |
  -------------------------------

3. Database
We store messages in files. Each file for us is a page (compare the
hardware-strategie).

Harddisc-memory
-------------
     ---------
     |   Block 1     |   <-- File 1
     ---------
     |  Block  2     |   <-- File 2
     ---------
     |  Block  N     |  <-- File N
     ---------

Summary
-------
We build a PDOM based on caching messages (DOM-Nodes). The
xmlBlaster-DOM-Tree will be divided in pages of nodes. DOM-Nodes are
cached in the RAM of your machine. Each-RAM-page is mapped on
a harddisc-file. The caching strategie is Write-Through with Write-
Allocation. We must build a XPATH-engine which knows when a node
is mapped on a database-file.

Further detail coming soon. I will start with the implementation next
week.

So long
Manuel

--
------------------------------------------------------------------------
| Manuel Kron,                        Mail:        manuel.kron at gmx.net |
| xmlBlaster                          http://www.xmlBlaster.org        |
| Office                              Phone: 07531 / 4545-00           |
| Radofzellerstr. 33, 78467 Konstanz                                   |
| Konstanz,Germany                    Phone(priv): (++49-7531) 282770  |
------------------------------------------------------------------------