| Prev | Next | Start of Chapter | End of Chapter | Contents | Glossary | Index | Comments | (7 out of 8)

Managing Source Code

When working on a large G2 project, especially in a team development environment, you will naturally build up several copies and versions of the source code. Managing the various copies and versions of the code is the focus of source code control (SCC).

Commercial Source Code Control System Features

Many commercial systems for SCC exist, most of which provide the following functionality:

Check in/check out - The ability for the developer to "reserve" a source code module, so that no one else can make changes simultaneously in the same module
Backup or version control - Preservation of older versions of the source code
Differencing- The ability to summarize the differences between two versions of a source code module

Using SCC Systems with G2

G2 applications present certain challenges for SCC systems:

G2 applications are partially encrypted.
Small changes such as moving an object to a different workspace can result in large changes in the saved KB file.

Because of these factors, it is not possible to use the differencing or dependency tracking features of commercial SCC systems. Additionally, the backup and version control systems usually must store the entire KB file, instead of just incremental changes, each time the KB is saved. Despite these limitations, SCC is still essential for managing G2 team development projects.

Note: Within the G2 5.x timeframe, G2 will support text-based KB files, which are not encrypted and will work effectively with most source code control systems.

Essential Features of G2 Source Code Control

The essential functions of an SCC system for modular KB development are:

Maintain the source files on a file server accessible to all team members
Allow a team member to check out a module, leaving a record that the module is reserved
Allow a team member to check in or commit a changed module, optionally releasing the lock on the file
Optionally provide update notification to team members possessing locks on dependent modules, when a new version of a supporting module is committed
Provide backups, for reference, for rollback, and in case of hard disk failure

Even when a commercial SCC system is not available, a competent system programmer can create a SCC system that provides these functions.

Using G2 Facilities for Source Code Control

Because SCC systems cannot provide information about what has changed in a KB, G2 provides several facilities for recording incremental changes:

The Authors attribute, found on most definitional items, such as class definitions, methods, procedures, and rules, records who made changes to the item and when.
The Change-log attribute records the full description of the prior state of an item when you make a change. You activate and deactivate the Change-log attribute in the Saving Parameters system table.

The change logging feature records the entire text of items such as procedures whenever you make a change. However, change logging only records incremental changes to class definitions, rules, and other small items.

Other Techniques for Source Code Control

Another technique you can use to manage source code is to create a procedure that writes all your methods and procedures to a file and then to compare the text of the file with earlier versions.

In addition, you might consider creating your own user menu choice for deleting an item or saving the KB, which checks the timestamp of the last module that was saved and warns you if a newer version of the module exists.

You can also use GFR to manage module versions and keep track of which versions the application requires to run.

For more information on using GFR for version control, see Version Control.

| Prev | Next | Start of Chapter | End of Chapter | Contents | Glossary | Index | Comments | (7 out of 8)

Copyright © 1997 Gensym Corporation, Inc.