4. Bridges: A set of interconnected tools

4.2. The Bridges Communication System and System Manager (CS)

4.3. Specialised "bridges" to transport models (GTF) and to GIS and Database managers (GTF_GIS)

4.4. Bridges Core Utilities (NIS): Bridging database structures attached to transport graphs

4.5. Bridges Expert System: Towards a Decision Support System (ES/DSS)

4.6. Bridges Data Sources Directory: The Bridges Digital Data Sources Guide (DDG)

Bridges research followed a highly interconnected and de-centralised development process, based on continuous feedback. As a result, all Bridges elements share fundamental concepts making them fully compatible with each other.

According to the "Value Stream" approach adopted, each Bridges Work package was led by one research partner who had to produce a specific deliverable defined to fulfil a precise user need, as illustrated in Figure 1. Bridges partners were urged by the coordinator to produce "throw away rapid prototypes" to provide a view of each partner's ideas and thoughts at an early stage of the research. Based on the analysis of these prototypes, and the spontaneous cross-fertilisation provided by the simultaneous viewing of all final deliverables, successive "evolutionary prototypes" were developed. This process allowed all partners to "begin with the end in mind", an essential requirement for highly innovative (so very risky) research projects.

Figure 1 Bridges Technology for building transport policy support systems
In more conventional "Stovepipe" management systems, work packages respond to the internal logic of the developer rather than that of the final user (consumer or client), and each one can be divided into different activities with many developers working with complex interrelations and input-output dependencies. While this management structure may be well suited to mature areas and mature partnerships (with little risk of failure at intermediate input-output steps), this is not the case for immature technologies (such as software development) and immature partnerships (based on heterogeneous multinational organisations) as in Bridges. For these cases the "value stream" approach adopted is much more suitable. This is illustrated in Table 1.

A Bridges brochure has been produced with a precise and synthetic description of the final research outcomes. This Final Report constitutes another step forward from that brochure in that it provides a clearer picture of what Bridges technology is because it includes the experience of partners developing real support systems using Bridges. Only the personal interaction with policy makers and experts, the practical observation of how much Bridges technology helps to solve their requirements in a productive manner, has helped the Bridges partners to communicate what Bridges technology is all about more efficiently.

As most Bridges tools remain at the expert level, they have to be used by system's developers to produce OPEN MULTI-SOFTWARE SUPPORT systems, fully customised to the needs of end users.

Some Bridges components can be used directly by end users because they have friendly interfaces (e.g. the DDG, NISystem routines, GTF-GIS Translator), some tools enjoy friendly interfaces even if they will be used typically by developers (e.g. the ES/DSS) and others have no friendly interface as such (e.g. the Communication System has to be configured by writing ASCII files according to an script language, self-explanatory for developers with experience but cryptic for most end users). A number of systems intended for very different end users has already been developed using Bridges tools for a variety of European and Local Public Administrations . For each one of these systems (see Section 11.2) a specific combination of tools has been applied.

In order to understand the technology, the Bridges tools can be differentiated by the different levels of expertise needed for their use:

• Specialised transport routines and applications, not available or poorly implemented in the market place, which can be used by non-expert users (e.g. DDG, some NIS routines),
• Ready-to-use applications and formats to be used by expert users to link advanced transport models to pre-existing systems (e.g. ES/DSS, GTF Format)
• Other tools to enable multiple software modules to work together in an integrated system (e.g. Communication System). They also allow the organisation and management of a number of personal user workspaces within the overall system and distributed via a Local Area Network. These are tools for expert users and system managers.

Bridges components are described below in more detail.

The Bridges Communication System harnesses OLE/COM technology to integrate stand alone applications. The Bridges Communication System is based on managing flows of command messages between stand alone applications. Bridges Communication System was designed to work in an Intranet but its decentralised architecture allows the addition of a new bridge to the Internet.

The Bridges Intranet Communication System facilitates simultaneous on-line dialogue with commercial applications . Transport models, even those supported by the few available OLE/COM compatible modelling packages, pose additional problems for "bridging" such as when they are based on independent non-interactive modules or they use incompatible data models. This requires more specific tools for example common data formats, such as Bridges/GTF.

In addition, "bridges" which allow different applications to share the same database were developed. However, the simple import and export of databases is not the main problem to be solved: The main problem is to define a common data model and format protocol for the exchange of complex transport oriented databases, which can grow into a standard for transport modellers.

The Bridges System Manager helps to personalise an open systems architecture to the specific needs of each user connected to it. Because of the modular and scalable character of systems developed by Bridges technology, each user has their own "personal Work space", which may contain different applications and different databases. "Friendliness" is therefore achieved by customising the architecture of the system to the needs of each specific user and problem. The Bridges System Manager allows an unlimited number of users to access the system, each with multiple customised workspaces. The Bridges Manager takes care of user passwords, work space maintenance and confidentiality issues.
Finally, the Bridges Common Interface allows the development of fully personalised menus and options, even beyond the design constraints of Microsoft Windows.

The Bridges Communication System, Management and User interface utilities have been programmed in Borland C++. Looking ahead, major improvements could be achieved by achieving Bridges communication through the Internet. Needless to say, this achievement would be a major step, placing Bridges technology in the forefront of software innovation.

A GTF (Generalised Transport Format) has been defined as a format to store and exchange any transport oriented database. Data exchange between transport models requires that models share a common data model. The GTF data model was defined to be sufficiently open to cover all strategic models at European scale. Bridges' aim is to propose GTF as standard format to be adopted by EC and international institutions.
The GTF data model is able to deal with the complex graph structures and topologies used by transport models (including demand, supply and specific modelling aspects). Following the IDEFIX approach to data modelling, the following entities were defined: node, link, interchange, route service, zone, main mode, persons/goods, carrier, modal stage, and flow/movement. The GTF data model includes the categorisation of relationships. In addition, the adopted GTF format description is public, compatible with international standards (UN/GESMES) and complementary to other database and GIS standard formats. It includes both topological information related to transport entities and the statistical data attached to them.

GTF has been tested with MKmetric VIA and MEAP MEPLAN modelling tools, and it has been extended to cover GIS in cooperation with the GTF_GIS work. A GTF Translator to and from VIA Model formats to GTF has been programmed, with a separate version in Java to allow Internet accessibility.

The GTF_GIS data model is based on adding transport topology to conventional GIS structures, according to the GTF definition (e.g. routes-route segments, stops. The format description is very intuitive with simple ASCII files.

GTF_GIS entities are compatible to GTF but can enrich public transport entities: links, nodes, turns, routes-route segments and segments, stops, changes, terminals, zones, fictive links, matrices-flows, vessels, units-persons/goods and milestones. Topological information related to entity relationships (e.g. allowed vessels and units on links, routes and flow matrices) is also included. Names of data tables containing statistical data and metadata information are listed within GTF_GIS but the actual data is not included.

Arc/Info, one of the most advanced GIS, is unable to handle the complex network topologies required for transport modelling (e.g. defining centroid's connectors, public transport routes and services etc.). Because of the high GIS productivity of Arc/Info tool, and its widespread use within European institutions, a specific "bridge" from Arc/Info's encrypted data format to GTF has been developed. The translator converts the Arc/Info GIS format into GTF_GIS by adding transport topology. A GTF_GIS-Arc/Info translator has been programmed based on MapObjects libraries, the only way to overcome the Arc/Info encrypted data format. The unavoidable use of such libraries makes the translator not totally royalties free.

Translators to standard CAD (DGN, DXF), GIS and Desktop mapping (MIF, SHP, GEO) formats have also been programmed. Given the limited GIS capabilities of these tools, they are unable to support advanced transport database structures. The interest of bridging these formats lies in the import of graphs developed on CAD, simple databases on GIS and the export of results to be displayed graphically. These translators have been programmed in Borland C++. Translators to DBS applications have been programmed based on ODBC drivers and Data Access Objects (DAO).

Bridges Core Utilities (Network Information System, NISystem utilities) have been developed as external stand alone applications to be linked to any system by the Bridges Communication System, just like any other stand alone application. This guarantees that systems developed by Bridges are fully scalable and independent even from Bridges own Core Utilities. Any Core utility can be removed and/or substituted by others when needed.

The paramount goal of NISystem Core Utilities is to complement transport modelling, GIS and DBS applications with missing utilities, particularly in the context of the ETIS reference requirements. NISystem provide:
§ Specialised routines for harmonising heterogeneous transport oriented databases and graphs. Examples are "Graph matching" utilities to "bridge" databases attached to graphs with different link segmentations covering the same zone, "Graph checking" utilities to check topological properties on CAD files, "Graph editing" utilities to modify graphs and add topology to CAD files etc.).

• An original GIS binary format (MGS), based on GTF and GTF_GIS data models has been created to increase the productivity of CAD-GIS core utilities and also to overcome possible confidentiality concerns for data dissemination.
  
• Graphic management routines for CAD, Desktop mapping and GIS have been programmed and included in the system as "core utilities", mostly to support "bridges" which required more than simple data format exchange (e.g. the above-mentioned Graph matching). Moreover, core utilities facilitate maximum flexibility in customising user interfaces and also make Bridges technology not completely dependent on commercial applications but complementary to them.
  
• A complete database management application has been programmed in Visual Basic 5.0, allowing an optimum degree of user interaction with large and complex databases as well as enjoying several management utilities. Bridges database manager uses Microsoft MDB as default data format but is open to other formats through standard ODBC drivers and DAO.
  
• Operational research and statistical algorithms for analysing transport databases have been plugged into the system to provide Bridges users with specialised easy-to-access tools for checking, exploring and exploiting databases.

Core Utilities have been programmed in Borland C++ (CAD, GIS and Operational research algorithms) and Visual Basic 5.0 (Database management, EXCEL macro-language).

NISystem utilities have been encapsulated in a number of modules (e.g. the DATABASE module contains all Visual Basic DAO-based functions to manage databases, as well as Microsoft Graph; VIEW contains all C++ routines to provide GIS visualisation capabilities; GRAPH contains all C++ routines providing edition, quality control and analysis of transport networks as graphs etc.). Each NIS module is an executable file which enjoys its own user-interface. It can be activated in the user-interface of the system similarly to any stand-alone application, simply by placing a button linked to the execution of the module.

ES/DDS has been developed and integrated into Bridges' toolbox to provide a tool to build intelligent translators between end users questions and sophisticated transport model outputs. The Bridges Expert System helps users to establish legitimate queries to models and interpret the model results. The ES has been tested by building the expert translators to MKmetric VIA, MEAP MEPLAN, and with the Spata Airport environmental impact model. ES/DSS has been defined and programmed with a medium and long-term ambition: the more sophisticated and numerous are the models "bridged" to ETIS, the more useful the ES/DSS tool will become in providing the expert interface.

ES/DSS architecture is composed of a user-interface (Object Oriented Interface, OOI) and the Expert System (ES). The OOI comprises a set of menus, forms, dialogue boxes etc. which are either pre-set or generated at run-time to facilitate user dialogues. The design part of OOI guides the expert user though the standard options of calling up a DSS module (data dictionary, template parser, expert system etc.) or a utility (Visdata, DSSview etc.).

The main task of the Expert System (ES) is to analyse user queries, decompose them into queries to be passed on to other modules, and to combine results into a meaningful form for the user to understand. In doing so, the ES may apply default values, assumptions and rules to fill in any missing data required for running other modules. ES comprises a Template parser, a Query processor, an ES Shell and a Multicriteria evaluator.
ES/DSS has been programmed in MS Visual Basic 5.0, Visual C++ 5.0, Access 7.0, ESRI's MapObjects 1.2 and Amzi! Prolog 4.0, according to OLE/COM. DSS is an OLE container application, therefore easily "bridged" to the rest of the components of a multi-software system by using the Bridges Communication System.

DDG has being developed as a stand alone application which contains European data sources and database descriptions (based on ETIS definitions). DDG follows a similar approach to the "Directory of Transportation Data Sources" published each year by the US Department of Transportation (Bureau of Transport Statistics).

The rational for including DDG in Bridges Toolbox was the assumption that ETIS (as with any other support system) would be limited to a minimum core of data useful for most studies, with links to additional data source providers as needed. On the other hand it was important to develop a public directory of transport information sources in Europe in the framework of Bridges to demonstrate the value of such a tool in the frame of policy support systems.

Currently, DDG is a data sources directory which contains updated information related to the main European Data providers and Data products, as well as available transport models and software products. Initially, DDG was focused on information databases and sources available in electronic format (CD-ROM) and sources accessible throughout the Internet but it was subsequently enriched by including sources available in conventional paper-form. It was also extended to cover available models/modellers and the major software products/providers.

DDG contains:

• 558 European database products, providing information such as availability, cost, periodicity, legal reference, data etc.,
• 732 European information providers with contact information and Website summaries,
• 85 modelling products with information based on previous studies undertaken by DGVII,
• 76 modelling providers with contact information,
• 71 software products and
• 74 software providers have also been included.

DDG has a user friendly interface to define queries and achieve customised answers, as well as to establish direct links to data sources through their Internet Websites. It also allows users to update the directory themselves; therefore, it includes a precise codification of fields and checks to validate any new information introduced. DDG has been programmed in MS Visual Basic 5.0, and information has been obtained from a variety of sources.

info@mcrit.com