Re: [xml-dev] Need a language whiz: An XML Schema "specifies" howdata is

SGML has the idea of a "document type" which had a "definition", part of which was achieved by the "declarations" i.e. the DTD. Due to the limitations of any schema language, the document type definition would never be entirely specified using the various declarations available.

XML Schemas does not have the concept of a document type or language as such: it has groupings of element types of namespaces, at least one of which will be a global declarations suitable for the root element. For Roger's enquiry, perhaps saying that the schema declares element types in namespaces, and valid documents conform to these types, is a good approach.

(Schematron also does not have an idea of a document type: it has patterns arranged into phases, where the context of some rules may be the document element. A "Pattern" is an ad hoc "type".)

Regards

Rick

On Thu, Jan 4, 2018 at 3:24 AM, Michael Kay <mike@saxonica.com> wrote:

The essence of the semantics of XSD is that the specification defines a process, variously called "validation" or "assessment", that takes a schema and an instance document as input and produces an assessment outcome as its result.

assess(schema, instance) => outcome

(It's slightly more complicated than that because you can specify other inputs to the assessment, e.g. strict/lax).

The specification does not use any specific term (such as "describes" or "constrains") for the relationship between a schema and the set of instance documents for which assessment has an outcome labeled "valid". You're perfectly welcome to use a term such as "describes" for this relationship if you wish, but it's not a term-of-art in XSD itself; so if you use it, you should say carefully what you mean by it.

Michael Kay
Saxonica

> On 3 Jan 2018, at 14:40, bryan rasmussen <rasmussen.bryan@gmail.com> wrote:
>
> The word choices betray viewpoints of reality -
> stating or specifying how data is to be structured assumes a blank
> canvas and the schema tells you how that canvas may be filled
> constrains assumes that data is a realm of many, perhaps infinite
> possibilities, XML Schema then constrains or limits the possible to
> the manageable.
>
> I am a specifying how data is to be structured man myself.
>
> On Mon, Nov 13, 2017 at 2:13 PM, Costello, Roger L. <costello@mitre.org> wrote:
>> Hi Folks,
>>
>>
>>
>> Which of the following is most accurate and why?
>>
>>
>>
>> An XML Schema specifies how data is to be structured.
>> An XML Schema describes how data is to be structured.
>> An XML Schema states how data is to be structured.
>> An XML Schema constrains the structure of data.
>> An XML Schema structures data.
>> An XML Schema describes data.
>> An XML Schema constrains data.
>> Other (what?)
>>
>>
>>
>> /Roger
>>
>>
>
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