A1 Modeller Concept

Abstract: This document is the concept for the A1 modeller, a tool that has evolved from the needs of the Haven project . End users may wish to see the A1 product page instead. See also A1 Modeller Treatment .

Availability: Public

Introduction - Basic Properties - Details - Formats - Release Conditions and End User License - Status - Future Work - References - Thanks - Copyright

Introduction

I've been frustrated many times by lack of a decent but simple modelling/diagramming tool. Visio is ok but it's really about diagrams, not models. Rational Rose is the other way around with in-depth developer support but poor on usability and very unflexible. Neither has decent export or open formats and both are expensive. Free/Shareware tools are not good enough (most are simple diagram/flowchart tools). Of open source applications only Dia (which is basically a Visio clone) is worth mentioning.

Basic Properties

A1 is an attempt to create a tool that fills the needs of primarily developers, without the rather extreme focus (and cost) of Rose but with the graphical flexibility and ease of use of more graphics oriented tools.

Fundamentally, it is a symbolic diagram editor. There is support for drawing basic shapes and lines, adding text and callouts, all with standard features like pens, brushes and fonts.
It has support for shapes. Shapes can be defined in a meta-drawing format (similar to WMF files or postscript) [secondary feature] or with static blueprints (image files) [secondary feature]
Each document (or model) can have several different views (or diagrams). Different views can show different properties of the document or different subsets of the content.

([secondary feature] indicates features that may not be fully implemented in the initial release.)

It has special support for development related content:

Support for UML diagrams with the usual symbols
Support for standard practice OOA/OOD/OOP symbols/models
Support for database descriptions/models
Support for flowcharts
Support for Design Patterns

It is flexible

Supports user defined objects, relations, shapes and composites
All definitions are specified in XML format with published semantics
Definitions can include behaviour [secondary feature]
Graphics format exports for use in other context such as documentation
Printing support with many options
Supports embedding in applicable contexts (OLE, KDE and GNOME, as applicable [KDE, GNOME secondary features]), both as container and as server

It has support for team development

Database support for storage allowing development teams to share data [secondary feature] as an alternative to XML documents
Repositories for sharing and reusing designs and constructs [secondary feature]

A1 does not feature

Code generation
Round-trip engineering
Electrical engineering (board or circuit layouts) applications
Focus on any type of trivial drawing applications such as floor plans or organization charts

The design priorities when creating A1 include

Flexibility
Ease of use
Openness and extendability
Output quality in external formats
Clarity

A1 is not designed with A1. The application architecture internally is less polished than the ones it is meant to support.

Using A1 to sketch an application or component design should be very straightforward. Start the application, and lay out the main building blocks in a view of your choice. For a larger or more thorough design, start in the appropriate views and apply your UML modelling skills. Integrating design fragments should also be relatively simple - for example a small state diagram fragment can easily be grafted onto a larger document, fusing the objects and states involved to those in the main document.
A1 does not enforce any design model or philosophy, nor is it meant to teach, endorse, advertise or tie the user to a product or manufacturer.

A1 is an enabler for the user, not a product for the maker.

Details

Shapes

Symbols

Object, class, state... symbols are the main building blocks when creating a document

Relations

Relations connect symbols. Together with symbols, relations are what the user is interested in when applying A1 to a problem.

Subsymbols

Handles, connect points, arrow heads and so on - the basic constituent parts of a diagram tool

Parts

The symbolic content parts of relations and symbols: properties and parameters

Definitions

Data types

A1 allows the user to define new data types and reuse them. Most of the data types used by the fundamental shapes in the application are defined in the same way.

Shapes

Shapes are defined in terms of constituent parts (member data), graphical properties and relational or semantic properties.

Diagram types (views)

Diagram types expose certain aspects of the document's (the model's) total data. An interaction diagram for instance shows the run-time interaction between object instances, while the class diagram shows the classes to which the objects belong and their structural relationships. Behind the views, the objects and the classes exposed in the two diagrams are connected and adding a method to the class in the class view makes the method available in the interaction view.

Formats

All application data is in XML using the semantics described for A1 (there will be a published format). This is also the document format for documents on file, and is the definition format for the built in types and user extensions. Database storage is slightly more complicated and not documented at this time.

Release Conditions and End User License

The initial plan for release is to release A1 as shareware. This means a time limited trial period after which a license must be paid or the application uninstalled. This shareware release would be for the Windows platform, specifically targetting Windows 2000 and later (including Windows XP but not Windows ME). Releasing A1 for open source platforms is under consideration - most likely this would be completely free and possibly in source form. The platforms under consideration are KDE and GNOME, compile targets primarily Linux (2.2 and later) and FreeBSD.

Status

A1 is currently (March 2002) under implementation. It will not be released until the basic feature set is completed. Whether it is released before the secondary features are implemented or not remains to be decided.

Temporary or intermediate working releases may appear in the A1 Product Page .

Current screenshot (click for full view )

Current Status

Features Missing

Lots of them.

Known Bugs

Most crash bugs are eliminated (in some cases by shutting off user access to a selection.
Opening/closing document views is still a crash bug. The same bug also provokes a crash when opening a view inside a host document (OLE).
OLE in itself does not work, possibly this is only caused by the previously mentioned view bug.
The model browser toolbox has a sizing bug causing it to gradually corrupt its display.

Future Work

Once the basic and secondary feature sets are completed further development will be considered. Extending the set of supported database platforms is one obvious feature. Depending on whether a non-Windows client is made or not (see above) there may be need for non-ODBC implementations as well. Apart from ODBC, the database targets are PostgreSQL (primary target), mySQL, Microsoft SQL Server, Oracle.

References

The UML specification - Rational Corporation
Grady Booch, "Object-Oriented Analysis and Design with Applications", second edition, The Benjamin/Cummings Publishing Company, Inc., 1994
Erich Gamma, Richard Helm, Ralph Johnson, John Vlissides, "Design Patterns" ("Elements of Reusable Object-Oriented Software"), Addison-Wesley (Addison Wesley Longman, Inc.), 1994
The XML Specification, W3C (World Wide Web Consortium, w3c.org )
Bjarne Stroustrup, "The C++ Programming Language", third edition, Addison-Wesley, 1997
"The PostgreSQL User Guide" and other documentation, www.postgresql.org

Thanks

Thanks to friends and colleagues who helped and provided input - especially Jan Mattsson and people at IT-huset, Ulf Lindbäck.

Copyright

This text was written in its entirety by Olof Ekström. For more information about the author of this page, see Olof Ekström's personal information in the Haven Project Profiles document.

Rational Rose is a registered trademark of Rational Corporation. Visio is a registered trademark of Microsoft Corporation.

In no way is the A1 Modeller or Extro System related to or endorsed by any other company or trademark holder mentioned in this document.

Bälinge/Uppsala, Sweden, February-March 2002