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10. The product architecture
Mobile client applications (PDA, phone) are connected to the server via the FreeTime protocol, which is a set of commands and notifications in a textual form that are sent via HTTP-protocol. The Internet-client application is implemented in PHP and is accessible from all the browsers that support JavaScript and CSS. Client applications for personal computers can also be connected to the server via the FreeTime protocol.
The server consists of the following components:
 FTVM
The FreeTime virtual machine FTVM performs all operations on schedule editing. FTVM provides a high-level object-oriented interface (API) which is a set of abstract C++ classes. There are special-purpose classes for scheduling objects, and supplementary classes for work with companies, sessions, etc. This API allows a user to create several sessions simultaneously, to load data for different companies, to modify data, to obtain solutions using different solvers, to save a modified model and obtained solutions, to receive notifications about changes in the project and to combine the projects. To save/read data, FTVM interacts with the data provider SDataProvider, and to recalculate a schedule, it uses the calculation provider FTCalcProvider.
FTSrv
The module FTSrv is the FreeTime server that contains implementation of the FreeTime protocol. It interacts with FTVM and provides maintenance, serialization and deserialization of objects, messages and notifications.
FTX
This module is an ISAPI extension for the IIS web-server. It presents implementation of the transport component of the FreeTime protocol and provides all needed transport functionality for FTSrv.
FTPHP
This module implements an extension for PHP4. It allows all classes and methods of FTVM to be accessible in php-scripts that are used in the FreeTime web-client.
FTCalcProvider
This is a set of modules for connection to different solvers. A module composes a task in terms of a concrete provider using the data from FTVM, starts computations and transfers the obtained solution to FTVM. At present, the provider for connection to the LSE computational engine (which is a part of the LEDAS Scheduler) is used.
SVM and SDataProvider
For data manipulation and storage, a library Strom (Structured Object Modeler) is used, which consists of an SVM and of the set SDataProvider.
An SVM - virtual machine of Strom allows any structured data to be stored as objects with slots. The SVM also provides a high-level object-oriented programming interface.
SDataProvider is a set of modules that supports a common protocol of data exchange with the SVM module. Each module from SDataProvider provides access to a certain data format/source. At present, an SFileProvider module is implemented for data storage in the files of a special-purpose-format Strom.
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