Table of Contents - APTAStandards.com

e given careful consideration for adoption as the basis for development of an
interchan ge specification for transit. This will require
significant efforts to define
common elements and aggregates of the transit industry specific data elements in XML.
Secondly, it requires definition of the APTA proposed message types
as XML schemas.
XML is widely accepted, and replacing a variety
of fixed and variable format messages
in other industries. With the rapid emergence of fast and efficient
XML parsers,
interface software development is minimized. XML parsers that create and breakdown
XML messages and convert them to and from
internal formats are widely available.
Microsoft is s trongly supporting XML throughout their software products, which
encourages even wider familiarity and adoption of the standard.
Tags theoretically add
bulk to data transmission, however,
this is becoming
less significant in practice with the
advent of faster and cheaper communication networks. Also, schemas are traditionally
more complicated than message layouts but are more powerful, describing
the
requirements, and enumerations of values in a consistent, and standard manner.
Extensibility is critical when designing a message protocol. A consistent problem with
fixed and vari able format messaging is that new needs are often difficult to
accommodate.
XML is easier to extend to new device and message needs.
4.3.3 Common Message Structure
Basic OFX data consists of a declaration and an OFX data block. The standard XML
declaration must come first, which includes an option to specify the version of XML
being used, and options to show such things as the encoding declaration and the
standalone status of the document as illustrated in Exhibit 4.3-2.
Exhibit 4.3-2 Processing Instructions
The OFX declaration must come next in the file with the following attributes as
described in the following list and Exhibit 4.3-3.
• OFXHEADER
• VERSION
• SECURITY
• OLDFILEUID
• NEWFILEUID
Page 33