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Key Differences between IMPA ETSF and MTML
MTML has been based, as much as practical, on the
IMPA ETSF EDIFACT messaging format. A tradeoff
has been made between human readability and understandability of MTML messages and the ability for IMPA ETSF users to utilize MTML with little effort and system rework. The latter has been the overall driving factor in MTML design. The intent has been to allow companies that have already invested in
IMPA ETSF to best leverage their investment, while not excluding other companies from readily participating in electronic marine purchasing transactions.
For example, the structure, sequence and content of MTML messages remain very close to that used in IMPA ETSF. Some key differences are listed below, and a complete bi-directional mapping between IMPA ETSF constructs and MTML equivalents is available through Member Services.
- IMPA ETSF is a subset of the UN EDIFACT standard. As such, it is designed to be produced and read solely by computers. MTML, on the other hand, is based on XML and can be produced and read both by computers and by people.
- IMPA ETSF therefore relies heavily on encoded and abbreviated constructs while MTML uses more explicit, human readable section names.
- XML inherently provides distinct message sections and does not therefore require the explicit message headers and trailers contained in
IMPA ETSF. Knowledge that had been contained in the headers and trailers has been incorporated into attributes of the message itself.
- For a similar reason, MTML has eliminated explicit message section separators.
- IMPA ETSF has been constrained to fit into the generic message structures provided by UN EDIFACT. In some cases, important business knowledge related to customer requirements has thus been forced into the same message section used for other non-specific information like comments. MTML separates the specific and non-specific information into distinct message sections, allowing the
former to be more readily visible and accessible for verification and automation.
- Similarly, some information that had been placed in generic messages in IMPA ETSF because of UN EDIFACT structures has been moved into attributes of the MTML message to allow for greater automatic validation by XML parsers. In some cases, this has changed the sequence of the message contents. At the same time, however, it has reduced the amount of information that must be transmitted and reduced the possibility of undetected transmission errors because of the automated validation.
- IMPA ETSF specifies a number of enumerated codes and qualifiers. If properly defined in a DTD, XML parsers are able to validate the use of these enumerated values in message content. However, XML does not support this capability for entirely numeric values. Therefore, an underscore has been placed before the IMPA ETSF numeric codes in MTML to support use of the automatic validation capability.
- IMPA ETSF prescribes the values for certain message fields such as information describing the version and controlling agency for the IMPA standard itself. MTML makes use of the XML capability to fix the values of these fields. These fields can then either be left out of an MTML message and automatically filled in, or put in the message and automatically constrained.
- All IMPA ETSF message segments and tags that are specified as not for use (“N” indicator) have been eliminated entirely from MTML.
- All EDIFACT tags that have to do with message segment counting and synchronization have been eliminated from MTML. The intent is to replace these with cross-industry standards being developed in this area such as the OASIS www.ebxml.org effort.
- MTML includes several extensions to more completely cover the marine trading process including support for requisitions, message exchange to vendors that may be
members of organizations other than IMPA (e.g. ISSA), support for additional contact methods (e.g. cell phone), support for specifying the tax exempt status of a trading transaction, support for prioritizing trades and line items, and support for specifying product quality guidelines on line items.