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Rail Industry Task Team
Electronic Parts Catalog Exchange Standard

Document Object Classes

• Images
  
  1. Bi-Tonal

     The Air Transport Association (ATA) has used TIFF for the standardized interchange of raster graphics for many years in its ATA 100 and successor ATA 2100 exchange specifications. A well defined profile of TIFF 5.0 using Group IV compression was specified and developed for raster interchange. TIFF is widely implemented, especially 5.0, although apparently Group IV implementations are not so widespread. TIFF 5.0 has been superseded by TIFF 6.0, but ATA's profile of TIFF 5.0 is still a valid 6.0 profile. (TIFF 6.0 added such features as Joint Photographic Exchange Group (JPEG) compression (which is alleged to be poorly specified) and Tiling - useful features for electronic technical documentation).

     AIT has successfully mapped ATA's TIFF 5.0 profile to TIFF 6.0 (TIFF 5.0 appears to be a true subset of TIFF 6.0). This means that in utilizing ATA's TIFF profile with Group IV compression, the Rail Industry will be able to use commercially available TIFF 5.0 and TIFF 6.0 products for implementing EPCES.

     With the completion of CGM:1992 Version 3, ATA declared its intention to migrate to the CGM Tile Array element for bi-level compressed (utilizing Group IV) raster content. Therefore development on the TIFF profile was frozen, and the only changes henceforth are defect corrections. ATA realizes that it will take some time for the market to supply the CGM-raster products sufficient to replace the TIFF products. The ATA strategy is therefore a sensible one, to transition from the old TIFF specification with its superior product availability to the newer integrated CGM specification, as product availability becomes adequate.

  2. Grayscale and Color
     The Rail Industry is deferring the inclusion of grayscale and color exchanges in the EPCES until ATA's specification for CGM Tile Array with JPEG is available. There are several factors making this an advantageous decision:
     • First, the only occurrence of grayscale images (there were no instances of color images) found in Phase II analysis of Rail Industry Parts Catalogs was in vendor marketing material included in a few of the catalogs. This appeared to be supplemental, not integral to the catalog.
     • Second, there is no formally adopted and widely implemented solution to the exchange of compressed color and grayscale images that has adequate product availability and reliability.

     As of this writing, JPEG registration for use in the CGM:1992 Version 3 Tile Array element is complete, meaning that the technical standards are in place. The corresponding ATA 2100 revision should be published in 2 to 5 months. The first commercial products should be available within 6 months of publication (obviously, the future is difficult to predict, but this is a reasonable estimate).

• Drawings
  The ATA has used CGM for the interchange of vector graphics for many years, in its ATA 100 and successor ATA 2100 exchange specifications. CGM is the only format allowed for interchange of vector graphics (for technical illustrations). ATA's CGM profile has evolved continuously for several years. The original GRExchange (Graphics Exchange) was based on Version 1 CGM in ATA 100, then on Version 3 CGM in ATA 2100.
  ATA was innovative in adopting the CGM:1992 Amendment 1 "Rules for Profiles" even before their completion, and has based its 2100 CGM profile on the Model Profile. The ATA CGM profile is the industry's most advanced and highest quality profile, for this reason in part. This strategy has resulted in certification testing available from The National Institute for Standards Testing (NIST). This is a critical determinant of the success of an open interchange program. Version 3 testing components should go on-line at NIST before the end of 1996.
  ATA has continued to develop its GRExchange with fixes and minor improvements, and will soon be adding JPEG compression for Version 3 raster metafiles. The main focus of ATA work now is IGExchange (Intelligent Graphics Exchange) — the utilization of Version 4 CGM to allow CGM graphics to be better integrated into hyperlinked documents.
  In the arena of technical documentation, ATA is clearly the leader in the development and application of CGM profiles. The profiles are close to State of the Art, and ATA's GWG committee is maintaining them well.
  Because the RIF application is so similar to some of the ATA applications, RIF has an excellent opportunity to follow the ATA CGM profile. In addition, to the quality of the profile work, RIF will thereby be benefiting as well from the buying clout of the aviation industry, and the certification testing service which is being set up. The RIF deviations to the ATA profile are listed in Section 3.5 and described in Section 2.1.1.3.

• Narrative Text
  The Railroad Industry Forum made the distinction between "narrative text" and "data". RIF regards narrative text as information that is 'free-flowing' (unstructured) text that serves as explanation or clarification of the catalog in part, or as a whole. Conversely, the notion of "data" is that of highly structured information concerning specific entities (i.e., parts) that may interface with a database or external processing system.

  Outside a catalog's "front matter", a functional parts catalogs should contain little narrative text. In an effort to minimize the ability to embed maintenance and operational information in a parts catalog, the RIF resolved to severely limit narrative text within the body of a parts catalog.

  1. Front Matter
     Narrative text contained in the front matter allows for general information pertinent to the catalog as a whole.
     1. General catalog identification

        Information concerning the catalog as a whole is captured in various elements and attributes of the root element ("rif-epc"). General Catalog identification includes the following information:

        • Original Issue Date ("rif-epc" attribute "oidate")
        • Version Number ("rif-epc" attribute "rev")
        • Revision Date ("rif-epc" attribute "revdate")
        • Document Number (see "doc-nbr")
        • Document Title (see "titleblk")
        • Volume Number (see "volume-nbr")
        • Document Provider Name and Address (see "provider-info")
        • Supersedure/Destroy Notices (see "notice")
        • Model Name/Number (see "model-name", "model-nbr")
        • General Effectivity Information (see "effect")
        • (see "rif-epc" and "epc-info")
     2. Introduction Section

        The only portion of the catalog's "front" section where free-flowing text can be authored is within the "intro" element of the DTD. While this "intro" is considered an Introduction, it can also be considered a "Foreword", "How to Use", "Abstract", etc. This introductory section should not include information concerning effectivity (see Section 4.3.1.4), Vendor Codes (see Section 4.3.1.5), Abbreviations used in the catalog (see Section 4.3.1.6), Alphabetical Index or Table of Contents (see Section 4.3.1.3). The RIF-EPC DTD allows for explicit tagging of this information outside the "intro" element in an effort to provide functional capabilities to the Electronic Parts Catalog.
        The EPC Introduction Section consists of: (see "intro")
        

        • numbered and titled paragraphs (see "topic", "subtopic")
        • unnumbered untitled paragraphs (paragraph text) (see "para)
        • sequential (numbered) lists, with subordinations (see "numlist")
        • random (bulleted) lists, with subordinations (see "unlist")
        • tables (see "table")
        • graphics (see "graphic")
        • footnotes within tables and text (see "ftnote" and "ftnref")
        • warnings, notes, and cautions (see "warning", "caution", "note")
        • cross references (see "refext" and "refint")
        • emphasized text (see "emphasis")
        • revised text (see "revst" and "revend")

     3. Alphabetical/Numerical Index, Table of Contents
        Found outside the narrative "introduction", these sections may include opening paragraphs. However, the actual index and table of content data should not be tagged as information. For the purpose of ensuring valid index data, these portions should be automatically generated, based on the contents of the EPC, at the time of processing. (see "index-sect", "toc-sect")

     4. Effectivity Cross Reference Information
        Throughout the EPC (at the catalog , chapter, section, subsection, figure, graphic, parts list, and part number levels), effectivity information can be captured. For example, different part numbers may require different model numbers; different figures provide for different car numbers. Usually, the effectivity information can be captured directly at the appropriate point. However, in some cases, the effectivity information (series of model numbers, serial number ranges, etc.) is grouped and categorized (ex. "Effectivity A") at the front of the manual, and referred to throughout the manual as a single letter. The RIF-EPC DTD allows for the creation of these effectivity groups.
        For example, suppose information concerning equipment model numbers is provided at the beginning of the manual. One group of effectivity is identified as "A" and covers Model numbers 8-645E, 8-645E3B, 8-645E3C, and 8-645F3B. Another group of effectivity is identified as "B" and covers model numbers 12-645E, and 12-645E3B, and 12-645E3C.
        The SGML markup for this information would be:
        

        &ltEFFECT-DATA>&ltEFFECT-CODE ID="A"&gtA</EFFECT-CODE>&ltMODEL-NO&gt8-645E</MODEL-NO>&ltMODEL-NO&gt8-645E3B</MODEL-NO>&ltMODEL-NO&gt8-645E3C</MODEL-NO>&ltMODEL-NO&gt8-645F3B</MODEL-NO></EFFECT-DATA>&ltEFFECT-DATA>&ltEFFECT-CODE ID="B"&gtB</EFFECT-CODE>&ltMODEL-NO&gt12-645E</MODEL-NO>&ltMODEL-NO&gt12-645E3B</MODEL-NO>&ltMODEL-NO&gt12-645E3C</MODEL-NO>&ltMODEL-NO&gt12-645F3B</MODEL-NO></EFFECT-DATA>
        

        A figure found in the body of the catalog is identified as being for model numbers defined in Effectivity Group "A". At this point, the DTD allows for either the Effectivity Code ("A") or the individual model numbers to be identified. To utilize the Effectivity Groups defined above, the markup would be the following:

        &ltFIGURE DRAW-NUMBER="f100" ID="f01">&ltEFFECT>&ltEFFECT-REF EFFECT-CODE="A"></EFFECT>&ltTITLE&gtENGINE EQUIPPED AND CRANKCASE AND OIL PAN ASSEMBLY</TITLE>....
        </FIGURE>

        
        It should be noted the mapping of the effectivity codes is accomplished through the use of the SGML Attributes for the elements "effect-code" and "effect-ref".

     5. List of Vendor's Code, Name, Address, Phone Number
        The Catalog front matter may provide an overall list of vendors, organized by Name, Address, and Phone Number, and referenced by a Vendor Code. Vendor Part Numbers included in parts lists must identify the vendor code through the use of the attribute "vendor-code" of the element "vendor-part-nbr". The DTD provides for explicit tagging of this information, in an effort to provide functional capabilities to the Electronic Parts Catalog. (see "vendor-list")

     6. List of Abbreviations
        The Catalog front matter may provide a list of abbreviations, explicitly tagged as groups of terms and definitions. (see "abbrev-list")

     7. List of Definitions
        The catalog front matter may provide a list of definitions, explicitly tagged as groups of terms and definitions. (see "def-list")

     8. Body Text
        The Task Team made a concerted effort to limit the ability to incorporate maintenance and operational information within their Electronic Parts Catalogs. To be in concert with best Industry practices, the RIF envisions separate DTDs developed for Functional Maintenance Manuals. However, the RIF-EPC DTD does allow for limited narrative text in the body of an EPC, provided such text can be 'linked' or associated with a specific figure, parts list, or part number. The RIF-EPC DTD defines two elements to embody this narrative text: "Associated Text" (see "assoc-text") and "Supporting Table" (see "support-table").
     9. Associated Text
        Associated text is considered as supplemental textual information associated with a figure, parts list, and/or an individual part number. The SGML Element "assoc-text" is therefore an optional element within the content model for a Figure ("figure"), a Parts List ("parts-list"), and individual items of a Parts List ("item-group", "subitem-group").

        Associated text can consist of:

        • General Notes (see "general"), which can contain a title and an numbered/unnumbered subordinated list.
        • Safety Notes (see "safety"), which can contain a title and an numbered/unnumbered subordinated list.
        • Warnings (see "warning"), which can include paragraph text and/or graphics.
        • Cautions (see "caution"), which can include paragraph text and/or graphics.
        • Notes (see "note"), which can include paragraph text and/or graphics.
        • Tables (see "table")
        • Graphics (see "graphic")

     10. Supporting Table
         The purpose of the RIF-EPC DTD is to model parts catalog information, specifically for electronic "point-and-click" navigation. The DTD, provided in Appendix A, appropriately models Electronic Parts Catalog Illustrations and Parts Lists to enable simple point and click navigation to achieve unambiguous part number identification. However, during the process of document analysis, it was found that interpretation of supplemental physical part characteristic information was sometimes necessary for proper part selection. This supplemental physical part characteristic information is to be captured in the SGML element for supporting tables (see "supporting-table").

         It should be noted that tabular information indicating physical part characteristics necessary for part selection could be encoded using the SGML element for Associated Text (see Section 4.3.2.1). However, since such physical part characteristic information is critical, during the part selection process, an effective EPC processing system should handle a "Supporting Table" differently from a general table provided as "Associated Text". The Supporting Table is an optional element within the content model for a Parts List ("parts-list"), and individual items of a Parts List ("item-group", "subitem-group").

         Individual part numbers can be explicitly linked to a supporting table using the attribute value "supp-table", the value of which would be the ID value of the "support-table" element. In addition, individual part numbers can be explicitly linked to an individual entry within the supporting table using the attribute value "supp-tbl-ent", the value of which would be the ID value of a specific row in the supporting table. Once within a Supporting Table, the attribute value "item-ref" (the value of which would be the ID value of the "item-group" or "subitem-group" elements) provides an explicit link back to the Parts List Item. In addition, attribute value "parts-list-ref" (the value of which would be the ID value of the "parts-list") provides an explicit link back to the Parts List as a whole.

         See Appendix C for Supporting Table examples.

• Data
  
  1. Part Information
     The purpose of the RIF-EPC DTD is to provide part information during the course of rail equipment maintenance and for input to Railroad accounting applications. A basic EPC utilizes the traditional detailed parts lists ("parts-list") to capture the information necessary for part selection. Part information which can be encoded using the DTD includes:
     • Link to figure where part is illustrated (attribute "fig-ref" for element "parts list"; also see Section 4.6)
     • Internal cross reference link to other portion of document (see "ref" within "nomen-col")
     • External cross reference link to other document (see "ref" within "nomen-col")
     • Effectivity information (see Section 4.4.3 below) (see "effect" within "item-group", "subitem-group")
     • Relationship of part with it's assembly or subassembly (see "part-nbr" attributes "higher-assem" and "assem-lvl")
     • Relationship of part with it's attaching parts (see "attach-parts")
     • Part description, capturing the noun (ex "Bolt"), additional description (see "nomen-col")
     • Quantity (see "qty")
     • Unit of Measure (see attribute "um" for element "qty")
     • Vendor Part Number and Vendor Code ("vendor-part-nbr"and attribute "vendor-code")
     • Purchaser Item or Customer Item Number ("pur-item-nbr")
     • Vendor Drawing Number (attribute "vendor-draw-nbr")
     • Vendor Revision Drawing Number (attribute "vendor-rev-draw-nbr")
     • Component Location Code ("comp-location")
     • Revision number, revision date (attributes "rev" and "revdate")
     • Supporting physical part characteristics (see "support-table")

  2. Drawing Data
     Information about individual illustrations can be captured using various elements and attributes defined in the RIF-EPC DTD. The element "epc-fig" groups a figure with it's parts list in the DTD. These groups of figures and parts list may be collected in sections or subsections of a chapter. A figure is actually a collection of a figure title and at least one graphic image. The seller code associated with the figure can be identified with the attribute "seller-code" on the Figure. Drawing numbers for individual graphic images can be captured with the "graphic" element's "draw-nbr" attribute. The image is identified using the "graphic" element's "filename" attribute.

     If the graphic is to be handled as a "foldout", the attribute value "foldout" for the "graphic" element should indicate "yes". This is a paper paradigm that has no relevance to an EPC, however, it will have importance to a publishing system.

     Revision number and revision date can be captured for the figure as well as the graphic image using the "rev" and "revdate" attributes. Effectivity information can be captured for the figure and graphic image using the "effect" element.

  3. Effectivity
     Effectivity is used to associate a given set of information (illustration, part number, etc.) to a distinct category of products, and is essential for proper part selection. The RIF-EPC DTD allows effectivity information to be captured at the following hierarchical levels of an Electronic Parts Catalog: The Catalog, Chapter, Section, Subsection, Figure, Graphic Image, Parts list, and Part Number Levels. The effectivity information that can be captured at these levels includes:
     • Model name/number (see "model-name", "model-nbr")
     • Serial number (see "serial-nbr")
     • Equipment number (see "equip-id-nbr")
     • Lot number (see "lot-nbr")
     • Serial range (see "serial-range")
     • Equipment range (see "equip-id-range")
     • Lot range (see "lot-range")
     
     In an effort to provide functional capabilities to the Electronic Parts Catalog, the low and high numbers of the serial, road, and lot ranges are captured in attribute values "low" and "high".

     Alternatively, an effectivity reference code ("effect-ref") can reference effectivity information that was defined in the Effectivity Cross Reference ("effect-xref") element (see Section 4.3.1.4 above).

  4. Physical Part Characteristics
     As discussed in Section 4.3.2.2, association of part-specific data is sometimes necessary for proper part selection. In such cases a specific part cannot be selected based on a "point-and-click" from an illustration. Rather, multiple part numbers are thus identified and additional information reviewed to select the desired part (See Figure B-9 and B-10 in Phase II Document). This additional information is to be encoded as a "supporting table" and can be linked from the individual part numbers or from the entire parts list.

  5. Revision Control
     The RIF-EPC DTD provides for the tracking of revision numbers ("rev") and revision dates ("revdate") on all hierarchical elements in the DTD. The requirement for the identification of this revision history will have to be defined under each specific rail vendor/ rail company contract.

  6. Links
     The EPCES must support full 'point and click' navigation enabling the ability to drill down to the smallest component level.

  7. HyTime Links
     The RIF has concluded to limit the use of HyTime linking as follows:
     • A figure "callout" to another figure (for visual references)
     • A figure "callout" to an item-group (part number, effectivity, nomenclature, etc.).

     HyTime provides a representation of interconnections between and within components of information. The RIF-EPC DTD incorporates HyTime to provide interconnection between a point on a graphic (commonly a numerical "callout") to textual information or another graphic.

     To uniformly describe a graphic, EPCES overlays the actual graphic with a virtual 2048 x 2048 (2K x 2K) grid. Because EPCES uses a virtual grid, it is necessary to map the actual pixel value of the graphic to the virtual grid. This approach (mapping the actual graphic to the EPCES grid) enables the hot spot to be display device (hardware) independent.

     The graphic and hot spot may be thought of as a rectangle. A rectangle can be described by using two points: (left, top) and (right, bottom). The EPCES algorithm assumes that the graphic and hot spot are normalized rectangles (i.e., the left is a lesser value than the right and the top is a lesser value than the bottom).

     1. Grid and Graphic Definitions

        VGh = 2048			Virtual Grid Horizontal Size
        VGv = 2048			Virtual Grid Vertical Size
        Wg  =				Width of Graphic (Horizontal)
        Hg   =				Height of Graphic (Vertical)
        GSFh = VGh/Wg	              	Horizontal Grid Scale Factor
        GSFv = VGh/Hg                   Vertical Grid Scale Factor	

     2. Graphic Hot Spot
        The hot spot is defined by an upper left coordinate (ULx, ULy) and a lower right coordinate (LRx, LRy).

        ULx  = Upper Left Horizontal Position of Hot Spot (left of rectangle) (graphic)
        ULy  = Upper left Vertical Position of Hot Spot (top of rectangle) (graphic)
        LRx  = Lower Right Horizontal Position of Hot Spot (right of rectangle) (graphic)
        LRy  = Lower Right Vertical Position of Hot Spot (bottom of rectangle) (graphic)
        

     3. Translation of Graphic Hot Spot to EPCES Grid

        RX  =  ULx * GSFh		Upper Left Horizontal Position (left of rectangle) 	
        			        (Grid)
        RY  =  ULy * GSFv		Upper Left Vertical Position (top of rectangle) 					
                                        (Grid)
        RW  = (LRx * GSFh) - RX	        Width of rectangle (Grid)
        RH  = (LRy * GSFv) - RY	        Height of rectangle (Grid)

     4. Example
        The following is an example of the mapping algorithm utilized by HyTime in placing hot spots. This example illustrates how to map the actual graphic to the EPCES grid (determine and implement the RX, RY, RW and RH) values. In this example the desired graphic hot spot upper left coordinate (UL) is (220,360), the lower right coordinate (LR) is (240,380) and the width and height of the graphic is (256,512).
        • First, establish relative grid scale factor:

          Divide VGh by Wg 	(2048 / 256) = 8  (GSFh)
          Divide VGv by Hg	(2048 / 512) = 4  (GSFv)

        • Determine upper left-corner grid hot spot coordinates:

          Multiply ULx by GSFh  	(220 * 8) = 1760  (RX)
          Multiply ULy by GSFv 	(360 * 4) = 1440  (RY)

        • Determine lower right-corner grid hot spot coordinates:

          Multiply LRx by GSFh  	(240 * 8) = 1920     	
          Multiply LRy by GSFv  	(380 * 4) = 1520   

        • Obtain the grid hot spot Width (RW) and Height (RH) values:

          Subtract RX  from (LRx * GSFh)	1920 - 1760 = 160 (RW)
          Subtract RY  from (LRy * GSFv)	1520 - 1440 =  80 (RH)

        Figure 1

        The following is the HyTime encoding which implements the above sample hot spot:

        &ltGRAPHIC FILENAME=figure1>		&ltHOT SPOT ID=ID1.SPOT IDREF="ID1.TEXT" GRAPHIC=figure1 RX="1760"
        		RY="1440" RW="160" RH="80"><!(if there were multiple hot spots they would continue to be described as follows:)>		&ltHOT SPOT ID=ID2.SPOT IDREF="ID2.TEXT" GRAPHIC=figure1 RX=...
        		&ltHOT SPOT ID=ID3.SPOT IDREF="ID3.TEXT" GRAPHIC=figure1 RX=...
        		&ltHOT SPOT ID=ID4.SPOT IDREF="ID4.TEXT" GRAPHIC=figure1 RX=...
        &ltGRAPHIC>		

  8. DTD Navigational "Links"
     With the exception of linking to/from a figure 'hot spot', the functional "point-and-click" capabilities of an Electronic Parts Catalog will be accomplished by normal interpretation of the data constructs defined in the DTD. The content models for the hierarchical elements within an Electronic Parts Catalog Chapter allow for navigation and 'linking' to subordinate elements. For example:
     
     • The content model for "chapter" allows for navigation of it's sections.
     • The content model for "epc-fig" allows for linking of a figure with its parts list.
     • The content model for "figure" allows for linking of graphics with associated text.
     • The content model for "parts-list" allows for linking of part numbers with its supporting table and associated text.

  9. SGML ID/IDREF "Links"
     In addition, the DTD allows for explicit linking between some of the above elements by use of ID/IDREF attribute values. By using ID/IDREFs, it is not always necessary to interpret the DTD model to access desired information. In addition, sometimes cross referencing relationships cannot be achieved by DTD Navigation. The DTD uses ID/IDREF links in the following cases:
     • A Part Number ("part-nbr") can be linked to a figure via navigation of the DTD, or by use of the "fig-ref" attribute.
     • A Part Number ("part-nbr") can be linked to physical part characteristics identified in a Supporting Table (see Section 4.3.2.2) by use of the "supp-table" attribute.
     • The part number can also be linked to a specific row in the supporting table by use of the "supp-tbl-ent" attribute.
     • A Part Number can be linked to the part number for it's higher assembly by use of the "higher-assem" attribute.

     As described in Section 4.3.1.4, effectivity information defined in the "effect-xref" (Effectivity Cross Reference) Section can be referenced in the body of the EPC by use attribute "effect-code" of the element "effect-ref".
     Cross references to other portions of the catalog are achieved by use of the "Internal Cross Reference" ("refint") element. The attribute value "refid" for the element "refint" provides a link to any element within the tagged file with the attribute "id" with the same value. The attribute "reftype" for element "refint" provides information on the purpose of the cross reference. The possible types of reference include:
     

     • ADR - Additional Detail Reference. A lateral reference to other figures in the EPC displaying additional related details.
     • DBR - Detail Breakdown Reference. A reference to a figure in the EPC containing a breakdown of the part number in the part number field.
     • ILR - Illustration Reference. A reference to another figure in the EPC which displays related coverage.
  22 January 1996 Rail Industry Task Team Release 0.91 Electronic Parts Catalog Exchange Standard