*Subject:* DFDL: potential problem ALCON
re: idea for checksum calculations in DFDL <https://lists.apache.org/thread.html/r85112d45e552a1f5b467406aeeee0f0a4bcaf143372b95c8e72f2669%40%3Cdev.daffodil.apache.org%3E> We may have a potential ‘situation’ as part of our DFDL/Daffodil offering as follows… My DFDL schema development process consists of examining the exit codes of a four (4) part mechanism: 1. DFDL parsing – “Houston, we have a go.” 2. DFDL unparsing – “Houston, we have a go.” 3. *End-to-end source/destination data comparison – “Houston, we have a problem.”* 4. Intermediate xml validation against reconstituted data – “Houston, we have a go.” I have an *unintentional* error in my DFDL schema - unfortunately the data/schema is lost that created this situation. Per above, both parse and unparse execute successfully and xmllint validates Daffodil’s intermediate XML file successfully against the reconstituted/unparsed data as well against the DFDL [erroneous] schema. However, the source and target data are *NOT* congruent. This is one situation I did not anticipate this situation. This means, our model and incorporation of Daffodil in our situation leaves [albeit] a *possibility* to have an erroneous DFDL schema that will ultimately send data end-to-end but because the two [gateway] ends do not communicate directly w/ each other there is no way for the destination gateway to verify if the data is identical w/ the data received by the source gateway. To address above and perhaps along the lines of 'checksum calculations' re: IPV4 element, what is the collective opinion of having a SHASUM capability added to Daffodil allowing the parser to optionally ("invisibly") incorporate a SHASUM in the intermediate XML file allowing the destination unparser to validate the reconstitute the data against the incorporated SHASUM? Perhaps a lame suggestion, could Daffodil optionally insert a comment tag while parsing identifying it as a Daffodil inserted shasum comment which the unparser can identify and validate the reconstituted data. Thx in advance, v/r Attila
