[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Validation - Is it worth it ?
Recently I've been involved in building a validation process using a combination of schema based and rules (schemaTron) and it got me thinking about how much validation is the right amount. The 'type' of validation processing I'm talking about is that which might be performed at a B2B gateway and is perhaps better categorized as 'technical' validation (ie. basic structural conformance and some content) rather than business rules (although the distinction is pretty thin). From the business perspective, it is undesirable to reject any message and thus lose an opportunity to complete a transaction. So from this point of view one might imagine that validation at this stage should be minimal, perhaps not even full schema (or perhaps a 'more relaxed' version of the published interface). This might be justified on the basis that rules, perhaps in a business process engine or application logic, are better at determining whether a message is business processable or not. Plus one can always push messages to a manual process and let a human decide ! On the flip side, we want to protect the integrity of our operational systems from erroneous data and, perhaps the most obvious reason, validation can provide an optimization of the process in the sense that, when the interaction is asynchronous (and possibly long running), it may be preferable to let a caller know right away that a message has some 'bad data' rather than for them to find that out some time later after having received an initial acknowledgement of receipt. To me this highlights the conundrum of a desire for strongly typed [service] interfaces versus the looser coupling and tolerance to change that we also typically seek. I am trying to find the 'sweet spot' that allows through messages that 'may' be processable, but rejects those where even if directed to a manual (human workflow) process would still not be worth the effort. I sometimes refer to this as 'compatible' messages versus enforcing strict adherence to a technical specification. I also have noted that versioning service interfaces (or even just XML schemas) can be somewhat problematic and can exacerbate validation issues, and to some extent mitigates against using them for validation purposes, particularly if they haven't been designed with any extensibility mechanisms at all to accommodate 'non breaking' change (e.g. xs:any/anyAttribute). Some of you may be thinking 'is there a question here anywhere ?', sorry I have meandered on somewhat. What I'm really after is finding out what others have found to be a good approach to message validation and whether there are views about how to achieve a balance between optimizing business opportunity and rejecting 'junk mail'. Cheers Fraser.
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