tighten the XSD

[VladimirAlexiev]

@RalphTro @CraigRe who are the main devs of the XSD?

The XSD allows various empty lists and empty strings, and I don't see the rationale for this.
@dakbhavesh compensates this in #255 using Schematron.
But when it comes to single fields, it's better to tighten the XSD rather than defer to Schematron. Eg:

• epcList is required but can be empty, why? This can be fixed by changing minOccurs as follows:

      <xsd:extension base="epcis:EPCISEventType">
        <xsd:sequence>
          <xsd:element name="epcList" type="epcis:EPCListType" minOccurs="0"/>
  <xsd:complexType name="EPCListType">
    <xsd:sequence>
      <xsd:element name="epc" type="epcglobal:EPC" minOccurs="1" maxOccurs="unbounded"/>

• epc can be the empty string, why? Add a minLength facet in the code below:

		<xsd:simpleContent>
			<xsd:extension base="xsd:string"/>

---

Consider switching to RNC? (this idea was canceled quickly)

https://balisage.net/Proceedings/vol7/html/Lee01/BalisageVol7-Lee01.html example "equivalent schema in XSD using Annotations instead of comments" shows how much nicer is RNC compared to XSD, and #276 ​asks: is there any chance the group could adopt RNC as XML master schema?

• We have an open source RNC validator (branch of jing) that produces precise XPath info of the error, allowing a user to pinpoint it and to highlight it, similar to what Schematron does and allowing unified error diagnostics. I don't know of a XSD validator to output XPath error location.
• I can convert XSD to RNC using tools from https://github.com/VladimirAlexiev/rnc
• The opposite conversion is also easy

---

@dakbhavesh:

You can express (epcList and epcList/epc) more simply as epcList/epc: you cannot reach the inner element if the outer element is missing.

About string-length(epcList/epc) > 0: think this checks one epc not necessarily all. I think you have to do something like this:

• assert epclist/epc and count(epclist/epc)=count(epclist/epc[string-length()>0])
• or if Schematron has "negated assert" then raise error on epclist/epc=""

[dakbhavesh]

Thanks, @VladimirAlexiev for improving the assertion and make it concise but needs a bit of correction to make it work. Regarding "negated assert" I tried following and it worked.

<sch:report test="epcList/epc[string-length(text()) = 0]">
      all elements in epcList must be non-empty
</sch:report>

report - triggers when the condition evaluates to true
assert - triggers when the condition evaluates to false

above is POC of what's all possible with Schematron

[VladimirAlexiev]

@dakbhavesh Isn't epclist/epc='' simpler?

[dakbhavesh]

I tried epclist/epc='' on http://xpather.com/ to but it wasn't able to detect the empty <epc> tags under epcList

[CraigRe]

EVERYONE check epcis 2.0 xsd, where anyuri, check to eliminate loophole for empty string, i.e., sting lengths should be nonzero. Minlength > 0 , provided that enclosing xml element is ITSELF optional within ITS enclosing xml element.
i.e., minoccurs = 0 , in order to avoid empty strings like this: