Database Architecture

Contents

• Abstract
• Introduction
• Implementation
  • Base Class for database related objects
  • Table - Userlist
  • Table - Projects
  • Table - Roles
  • Table - Role_Names
  • User Object
  • Project Object
• Files
• Database creation via Makefile
• Configuration Files
• Reference

Abstract

This document describes the organization of the ACDE data base. The Database is based upon the MySQL product. This document describes the tables in detail and the access methods used for these tables.

Introduction

The ACDE is based upon the data bases product MySQL. This is realtional data base with an SQL like query language. For support of this environement the following package are available:

For each object to managed in the ACDE a component does exist which hides the interface to the SQL database. The priciple is quite simple. An abstract base class for all data base related objects has been defined which requieres the implementation of the store/delete and get code. Key values are supplied to the implementation by means of attribute functions. The object may be loaded/stores or deleted by applying a procedure from the base class. This mehthod hopefully ensures an implementation independant from the data base system.

Implementation

Base Class for database related objects

In order to seperate the ACDE implementation from the data base part, a base class for all database objects has been defined. Towards the application it provides an interface, which does not depend on the underlying data base. In direxction of the data base system three procedues (store/delete/get) are required by the implementation of an data base object. These procedures do depend on the implementation of the underlying database system.

The class provides the following interface:

The life cycle of a typical data base object will most likely look as below:

Step 1. Create an instance

Step 2. Add the object to a database

Step 3. load the instance from the database

Step 4. Use the data / update

Step 5. Update the data in the database

.. go back to 4

Step 6. If desired the object is deleted by deleting it.

Instance creation of an data base object may be done by exp. specifying the data base object or simply leaving is empty.

item : User.Object( dbase );
...
Initialize( item, debug );

-- This step is done only if during instanciation, the dabase has not been referenced.
Data_Base( Item, dbase );

Loading instance data from data base is done by first setting the requiered key attributes of the object and then issuing the Load method. In order to verify that the object has been loaded completly, the status of the object has to be verified by means of the Is_valid attribute,

Name( item, "erdmann" );
....
Load( item );
if not Is_Valid( item ) then
            ... error handling ..
end if;  

After the object has been manipulated, the data in the database may be updated/delete by means of the Update method.

Update( item );
  or 
Delete( item );
...
Finalize( item );

A help full mechanism to keep dependent information upto date is the Watch feature. If an instance is updated, a list of procedures is processed which has been added to the object by means of the watch method. Each procedure is called with the following arguments:

procedure( source : in Object'Class; target : in Handle ); 

Where source is the changed object and target is the handle of the object which may depend on this object. The prcoedure may access the data of the source object by attribute functions to interrogate the changed data.

Table - Userlist

The userlist table contains all users of the ACDE environement and their basic properties. There are no consitency rules to other tables known.

Files

This section contains the table of all files and there purpose which are related to the databse of the ACDE. The path is taken relative to the ACDE source root directory:

Database Instanciation via Makefile

The database of test system may always deleted and rebuild by using the following make file commands in ./DB:

make cleandb
make newdb

The target cleandb deletes the whole ACDE database. Currently no tables are saved! After building newdb check always the contents of the *.log files for all tables.

Configuration Parameters

The configuration file db_config.def contains a data base section.

[db]
serverUser=ACDE_USER
server=SERVER
....

Constants are defined in the common.sql file.

References