Stage 1 - Introduction

About the Tersus Platform

Welcome to the Tersus Platform.

With Tersus, you can easily create web applications by drawing diagrams instead of writing code.

The Tersus technology has already been used successfully to create a range of software solutions, from small tactical applications to high-end, mission critical systems for processing financial transactions.

Tersus is especially appropriate for composite applications assembled from a combination of built-in components, self developed components and Web Services.

The Tersus Platform comprises three major components:

• The Tersus Studio, an extension of the Eclipse platform, used by modelers (developers and business experts) to graphically define the functionality of applications;

• The Tersus Model Libraries, containing building blocks for assembling applications;

• The Tersus Server, which executes the modeled solutions and performs the required database updates (can run over a J2EE application server).

Creating an application is done by defining a Model Hierarchy, in which each model is composed of lower level components. The developer starts at a top-level diagram representing the whole system, and then continues with an iterative top-down refinement process – drilling down from each model to specify its components. Employing an “infinite drawing board” that represents graphically the whole model hierarchy, it is possible for the developer to fully and precisely specify the required business logic in a visual and intuitive manner.

Deploying the application, once modeled, is immediate. The models are saved as a hierarchy of XML files, which are read by the Tersus Runtime Engine. The engine then performs the functionality defined by the models at all levels – user interface, server-side processing and database operations. It is possible to record the full details of the execution if tracing is required for auditing purposes or for root cause analysis of problems.

Maintaining an existing application is done by amending its model – changing the business flow, adding new components, or disabling redundant components. Upon completion of the required modifications, the application can be redeployed immediately.

About this Tutorial

This tutorial outlines the development of a complete sample application - a Purchase Requisition Management system - using the Tersus Modeling Tool.

The tutorial provides a step-by-step, hands-on example of the development of such a system, starting with an employee issuing a requisition, and concluding with the delivery of requested items.

Within minutes, and then at each step as you progress with building the application, you can start the application from your browser using the Tersus Runtime Engine.

Document Conventions

This tutorial uses the following style conventions:

Using the Tutorial

The tutorial is divided into multiple stages, each covering several new concepts of the Tersus development methodology.

In each stage, the tutorial covers:

- The development process (modeling, or "how to model it");

- The resulting application definition (model, or "how the model looks when done"); and

- The outcome (application, “what the user gets to use”).

Each stage is accompanied by a pre-built, functioning sample project implementing all stages up-to and including the current stage.

The aim of the sample projects is two-fold:

1. Provide a consistent reference when reading through the tutorial stages.

2. Provide additional functionality which is similar to functionality modeled in detail in the tutorial. You can use the samples and skip the modeling of the additional functionality, or decide to model it yourself (the additional functionality is described in short rather than in a detailed step-by-step manner, but given what you have done earlier in the same stage, these descriptions should be sufficient for you to model the functionality yourself).

It is highly recommended that you follow the tutorial stage by stage and in the order outlined.

The Sample Application

Acme corp. wants to replace its manual, paper-intensive purchase requisition process with a computerized web-based system that will allow employees to request the purchase of products (e.g. PCs, furniture, office supplies).

A purchase requisition always goes through, at the very least, the following steps:

1. An employee enters a new requisition;

2. The requisition is approved/rejected by the employee's manager;

3. The approved requisition is handled by a purchaser, who issues a purchase order;

4. When the items ordered are delivered, the requisition is considered fulfilled and closed.