RE: Fallacies of Validation ... RE: Are people really using Id
1) We haven't done it yet, but almost from the start of negotiations for a DTD for patent applications we recognized the need for multiple schema. Getting a filing date is a key event for an applicant, and current rules (paper or electronic) are geared to make that as easy as possible. A fee must be paid to get a filing date, but if not paid with the application, then the a notice is given to cure the deficiency by a specified date, or the application will be considered abandoned. If the fee is paid by that date, the original filing date is secured, and if not, the applicant has to start over. There are several other requirements for filing that follow the same pattern, so when validating data on the client side at the time of submission, applicants are given the opportunity to "override" error messages and send the (defective) application anyway. At later stages of processing, validation is more stringent, and different versions of the DTD or schema will ensure that human input can be properly processed by machine at later stages in prosecution. 2) If you are integrating legacy systems through an EAI hub, it may be that the only possible place for schemas and schema validation is at the outermost edge, that is, the boundary between the systems and the hub. Migrating legacy systems to newer technology is at least 50% a social issue, not a technical issue, so I'm not sure it's fair to characterize this as a fallacy. 3) For the last one, I'm not sure the "fallacy" is "you must validate" so much as "you must structure the data". Markup costs money, but it also adds value, and if there is no value extracted, then don't pay the price up front (unless your future is really uncertain and you'd rather incur a lower cost for structuring now than a potentially much higher cost in the future). If you do structure the data, in some cases it will pay to validate as well. For example, from the start of automation at the Trademark Office of the US Patent & Trademark Office, correspondence addresses were not structured, but captured only as line 1, line 2, etc. This worked fine until about two years ago when the USPTO wanted to decrease the cost of sending official notices to trademark applicants and registrants via US mail. The USPTO began using a service of the US Post Office whereby we transmit address/message pairs to them in bulk, and the Post Office prints postcards near their destination (domestic only), at a substantial savings to us over the cost of printing, postage, and moving around big bins of postcards. To do this, however, the Trademark Office had to provide addresses that were (minimally) structured. It was clearly a cost advantage to go to the expense of parsing all the addresses (millions of them) to the necessary structure (we're talking Department of Commerce gold medals, here). In a case like this, validating key components of the address (checking against an address database, for example) before transmitting to USPS ensures timely delivery of an official notice, and is judged worth the cost. Bruce B. Cox SA4XMLT +1-703-306-2606 -----Original Message----- From: Roger L. Costello [mailto:costello@m...] Sent: Wednesday, August 25, 2004 9:05 AM To: xml-dev@l... Subject: Fallacies of Validation ... RE: Are people really using Identity constraints specified in XML schema? Hi Folks, From reading yesterday's messages, I feel like the real issues are coming out. And the real issues, I perceive, are in the various fallacies with validation. Below I provide a start at listing the fallacies. Your help in elaborating these is needed. Fallacies of Validation 1. Fallacy of "THE Schema" 2. Fallacy of Schema Locality 3. Fallacy of Requisite Validation Let's examine each of these fallacies. 1. Fallacy of "THE Schema" This fallacy was identified by Michael Kay last week: > ... there's no harm in using XML Schema to check data against the > business rules, so long as you realize this is *an* XML Schema, not > *the* XML Schema. We need to stop thinking that there can only be one > schema. Yesterday Len Bullard made a similar statement: > ... most fundamental errors are ... to consider only a single schema. and at another point Len states: > ... fall into the trap of thinking of THE schema and not recognizing > the system as a declarative ecosystem of schemas and schema > components. Both Michael and Len are stating that in a system there should be numerous schemas. This is a big mindshift for me. I admit being trapped into thinking that there should be a single schema. It would be very useful if we could have a simple example that shows how several schemas might be employed, rather than a single schema. Could someone provide an example? Len, I like the term you used, "declarative ecosystem". Could you elaborate upon what this means? 2. Fallacy of Schema Locality Yesterday Len also identified this fallacy: > ... most fundamental errors are to consider schemas only at the > external system junctions ... Len notes that many people think that validation should occur at a certain place in the system, namely, at the outermost edges of the system. (Len, I assume this to mean the user-interface?) Len argues that validation can rightfully be done at many locations in a system. Len, perhaps some more words on this fallacy would be in order? 3. Fallacy of Requisite Validation Yesterday Michael Kay made a very compelling statement with regards to whether validation should be done at all in certain situations. Michael was responding to the example of an online service validating a user's address. Here's what Michael said about the online service's insistence on validating the user's address: > The strategy (validating the user's address) assumes that you know > better than your customers what constitutes a valid address. Let's > face it, you don't, and you never > will. A much better strategy is to let them (the user) express > their address in their own terms. After all, that's what they do in > old-fashioned paper correspondence, and it seems to work quite well. Michael argues very effectively that in this situation it makes no sense to do any validation at all! I have not yet read all of yesterday's postings, so I may have missed some other fallacies. If you know of any fallacies that I missed, would you please send them along? Also, if you have comments on the fallacies identified above, please send them along. Note: examples are much needed! /Roger
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