XML for Rail Systems Maintenance Documentation
ABSTRACT
ALSTOM Transport has developed with EURODOC standard for maintenance documentation..The project was initiated by a global rail system product documentation content creation challenge. It was then decided to replace the old linear and paper oriented documentation production mode by a new one leveraging the potential of electronic and modular documentation.
Table of Contents
1. Product data standard
1.1. Exchange format
For industry major corporations, when it comes to bind a set of documentation components produced by various internal departments, partners or suppliers in order to manage it in a centralized way and publish it with a set of selected tools, it is highly recommended to define a vendor-neutral exchange format handling both content and meta-content.
When it comes to publish on various media with their specific display features from a single content source without rewriting each time, it is highly recommended to use XML for content.
When it comes to factorize documentation components use, use them at different locations in publications or for different equipment variants, it is recommended to adopt a modular approach : to define documentation granules which are independents from their point of use, to identify and organise them in meta-content distribution so that they can easily be projected in publications.
Three years ago, ALSTOM Transport attempted to face such challenges beginning for a generic tramway equipment fitting well into this model. A standard to describe maintenance documentation was developed with EURODOC.
The first step consisted in defining an exchange neutral format. A neutral format must be independent from content creation tools to allow exchange of data throughout a documentation production, management and diffusion chain involving various actors and tools. This aspect, tools-independency, is probably the most difficult to handle as the actual content creators usually express their needs in the following way :
-
We want to use our popular word processor application to create documents,
-
We want to use our popular spread-sheet application to create document properties if really necessary.
As a corollary the content creation tools should try, as far as possible, to let the content creators habits unchanged. As we will see, this leads to technical oddities, and may in the long term be turned into more rational approaches.
The actors in the process must be able to inject into or extract from their system, neutral content. Typically in the project, neutral content as files structures is addressed by content providers to ALSTOM transport for integration into a PDM central repository.
Neutral format approach deals with encoding of documents and graphics modules content itself, but also of meta-content describing a collection of document modules. Modules for ALSTOM Transport are organized into two products top-down breakdown structure :
-
Functional,
-
Organic.
Concerning the meta data allowing to organize modules in products top-down breakdown nodes and describe attributes for these nodes, since the initial production environment was a well-known spread-sheet application, a simple ASCII delimited approach was adopted for exchange.
This organisation is directly inspired from the way data are managed in PDM systems but is actually independent of its use. It has the major advantage to be independent from the way modules will be projected into paper manuals or electronic publications, just describing the product in a generic way. As in many industrial sectors, the manuals used by maintenance operators are :
-
Maintenance manuals,
-
Descriptive and Functional manuals,
-
Illustrated part catalogs.
The difficulty to assume electronic document neutrality is typically an issue addressed by SGML or XML encoding for the textual components of documentation. At the very beginning of the project XML was at an early stage, it was then decided to use an AECMA 1000D derived SGML DTD for descriptive and procedural textual modules and to adopt an approach similar to IETP-L to build assembled manuals and to stay in the world of SGML technology.
It was decided to use JPEG, TIFF for raster and CGM as being the traditional neutral formats for graphics.
1.2. Modular approach
The modular approach was another key point of the project. Derived from the AECMA philosophy, documentation modules are created independently from their point of use in a set of technical manuals. A same module can be assigned to several points of use in product documentation. It is not strictly affected to a product variant but can be re-used for different ones managing the notion of effectivity. An assembling specification, hold in an XML file, gives the content and structure of each manual.
This approach is extremely powerful and seems ideal, but it is also a technical challenge because the human decisions concerning content creation and the whole software chain must be modular-aware.
1.3. SGML to XML
During the course of the project it was decided to switch from SGML to XML, the expected benefit was to replace old generation SGML tools by mass-market, standardised and robust software tools brought by the XML wave. This had a serious impact on AECMA-derived DTDs which had to be simplified according to XML shortcuts, but left the structured content mainly unchanged.
2. System design
We currently distinguish three stages in a global documentation management system documentation :
-
The production system,
-
The management system,
-
The diffusion system.
Using XML to encode content allows to streamline its circulation from production to diffusion using the large scope of standard XML transformation processes. The Figure 1 illustrates the general architecture implemented for ALSTOM.
2.1. Production system
A production system enables the production of documentation modules. Initially the SGML editing environment was MS WORD adapted, according to technical writers requirements. A specific environment constrained by an RTF style sheet and macros was developed. RTF structure was converted to SGML using a DTD-adapted converter developed in BALISE language. This tool was successfully used in production environment, The main problems using such an environment were :
-
Lack of real-time validation,
-
Specific error recovery to develop,
-
Necessity to deploy SGML parser engine and scripts minimizing the actual advantage of using MS WORD which is supposed to be widely spread,
-
Specific conversion program to develop and maintain,
-
High maintenance impact as the DTDs evolve.
Seizing the opportunity of SGML to XML switch, in order to gain on quality control, this MS WORD editing environment was replaced by a native lightweight XML editor. This environment was finally well accepted by technical writers not really hostile to tags when understanding the fundamentals of structured documentation.
Graphic are extracted through relevant filters from main technical graphic production environment, in this context, the AUTOCAD to CGM filters available on the market were used.
2.2. Content management system
Once produced, content must be managed. For large volume, collaborative work, configuration management a simple file system storage approach quickly reaches limitations in the field of data integrity and limits also the potential to automate data processing.
Content management needs are different for the industry integrator centralizing the content in a single point and major content providers having to enable collaborative technical writing and prepare documents sets for deliveries on a regular basis.
ALSTOM transport managed documentation granules attached to PDM documents storage module along with technical data attached to the rail system.
As a major content provider. EURODOC developed its own management system on a popular DBMS system being enriched with basic electronic document management features such as :
-
Versioning,
-
Meta content data management including,
-
Check in / Check out,
-
Access Control Lists,
-
Secured storage,
-
Distributed collaborative framework based on WEB standards.
This kind of lightweight highly-flexible, documentation production management system should be the backbone information system of any major content provider interacting with major industry players.
2.3. Diffusion System
When trying to convince about XML structuration, we often stress on the ability to deploy electronic interactive documentation on WEB or CD. Traditionally, the paper or electronic paper (PDF) requirement is first to occur. Technically speaking, it is often more difficult to produce paper with complex page setting requirements just because the corresponding software tools did not evolved at the speed of WEB technologies. Finally the success of an XML implementation often depends on the ability to still produce paper, as before.
Based on an assembling specification in XML, manuals assembly is automated using XML transformation languages. The result, as a linear large SGML manual, is sent over a popular page-setting software. application. The page setting application is exporting PDF directly. As a typical oddity, the page-setting application is still SGML-aware (through an import application), but not XML. Once the chain was switched to full XML, an XML to SGML converter had to written to keep compatibility.
It is currently under study to replace the page-setting application by a fully automated XSL FO based process.
HTML table of contents and module contents are also automatically produced to be used in a documentation Intranet portal and electronic publications. All of the diffusion system makes intensive use of XML transformation technology through XSLT.
3. Use in real life
This system has been successfully deployed and used for production of tramways metro and train documentation for more than one year. It demonstrates which functional requirements can be achieved in the field of documentation production, which technical choices are reasonable for the current time and evolutions expected through the use of latest XML evolutions. It has also reduced the the documentation price by giving us the ability to reuse information.
As an extension showing the potential of diffusion, ALSTOM has developed a system to manage and to consult information at the maintenance depot level. This system is coupled with the MMS system (Maintenance Management System). When a user access an information (procedure, illustrated part catalog, wiring diagram), this information is computed according to the train and according to the evolutions that have been applied to the train (system) he has to maintain. This improve the global system availability which is time and cost saving.
Modularity and product based structuration has made that possible .This system is developed using the WEB technology.