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aj-stein-nist/condtional_has-cardinality_559_instance-1.xml

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condtional_has-cardinality_559_instance-1.xml
<?xml version="1.0" encoding="UTF-8"?>
<foo xmlns="https://github.com/usnistgov/metaschema/issues/559">
<bar grouping="three-only-group">a</bar>
<bar grouping="three-only-group">b</bar>
<bar grouping="three-only-group">c</bar>
</foo>
Raw
condtional_has-cardinality_559_instance-2.xml
<?xml version="1.0" encoding="UTF-8"?>
<foo xmlns="https://github.com/usnistgov/metaschema/issues/559">
<bar grouping="two-only-group">a</bar>
<bar grouping="two-only-group">b</bar>
</foo>
Raw
condtional_has-cardinality_559_metaschema.xml
<?xml version="1.0" encoding="UTF-8"?>
<?xml-model href="https://raw.githubusercontent.com/usnistgov/metaschema/develop/schema/xml/metaschema.xsd" type="application/xml" schematypens="http://www.w3.org/2001/XMLSchema"?>
<METASCHEMA xmlns="http://csrc.nist.gov/ns/oscal/metaschema/1.0">
<schema-name>Model for conditional has-cardinality modeling for usnistgov/metaschema#559</schema-name>
<schema-version>0.1.0</schema-version>
<short-name>conditional-has-cardinality-559</short-name>
<namespace>https://github.com/usnistgov/metaschema/issues/559</namespace>
<json-base-uri>https://github.com/usnistgov/metaschema/issues/559</json-base-uri>
<define-assembly name="foo">
<formal-name>Root Assembly</formal-name>
<description>The fields of this assembly should count either on two-only-group or three-only-group.</description>
<root-name>foo</root-name>
<model>
<define-field name="bar" as-type="string" min-occurs="1" max-occurs="unbounded">
<formal-name>Bar Units</formal-name>
<json-value-key>value</json-value-key>
<group-as name="bars" in-json="ARRAY"/>
<define-flag name="grouping">
<constraint>
<allowed-values allow-other="yes">
<enum value="two-only-group"/>
<enum value="three-only-group"/>
</allowed-values>
</constraint>
</define-flag>
</define-field>
</model>
<constraint>
<has-cardinality id="only-two" level="ERROR" target="bar[@grouping='two-only-group']" min-occurs="2" max-occurs="2"/>
<has-cardinality id="only-three" level="ERROR" target="bar[@grouping='three-only-group']" min-occurs="3" max-occurs="3"/>
</constraint>
</define-assembly>
</METASCHEMA>
@wendellpiez
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wendellpiez commented Mar 1, 2024

Point #1 - as a design, I am bothered that the @grouping flag appears on the thing being grouped. I'd have expected

<foo xmlns="https://github.com/usnistgov/metaschema/issues/559" grouping="three-only-group">
    <bar>a</bar>
    <bar>b</bar>
    <bar>c</bar>
</foo>

while in the abstract I suppose there might have been a reason to place the indicator on the leaves here.

This being the case I think we need more rules for the use case:

  1. The groupings must all be the same
  2. Any grouping must correspond to the number in the group

Assuming every bar carries a @grouping, as @david-waltermire-nist says, this can be expressed parsimoniously using expect (on the foo parent):

<expect test="not(bar/@grouping != bar/grouping)]">bar/@grouping must be the same ...</expect>
<expect test="not(bar/@grouping='two-only-group') or count(bar) = 2">...</expect>
<expect test="not(bar/@grouping='three-only-group') or count(bar) = 3">...</expect>

Together these rules have the desired effect.

This suggests to me that we should address the larger concern about the (misleading) name target on has-cardinality without altering semantics at a deeper level.

@wendellpiez
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wendellpiez commented Mar 1, 2024 •
edited
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Also of note: here is a sample that passes the test as given, which is actually not self-contradictory

<?xml version="1.0" encoding="UTF-8"?>
<foo xmlns="https://github.com/usnistgov/metaschema/issues/559">
    <bar grouping="two-only-group">alpha</bar>
    <bar grouping="two-only-group">beta</bar>
    <bar grouping="three-only-group">a</bar>
    <bar grouping="three-only-group">b</bar>
    <bar grouping="three-only-group">c</bar>
</foo>

This might be more evidence that the meaning of the has-cardinality as given, especially as it interrelates to other rules (it doesn't), is unclear....

This can be inhibited, again, with an expect.

@aj-stein-nist
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aj-stein-nist commented Mar 1, 2024

So just to be clear, I made this example, that is generally silly, to illustrate a specific point without a lot more context in the computer model in usnistgov/metaschema#554 was a little more elaborate, I do not disagree there. This is the practical example where it was not very practical flag on the root assembly and the cross-referenced field is "higher up" in the tree of the node item. That is the model and example there.

<?xml version="1.0" encoding="UTF-8"?>
<?xml-model href="https://raw.githubusercontent.com/usnistgov/metaschema/develop/schema/xml/metaschema.xsd" type="application/xml" schematypens="http://www.w3.org/2001/XMLSchema"?>
<METASCHEMA xmlns="http://csrc.nist.gov/ns/oscal/metaschema/1.0">
  <schema-name>Computer Model</schema-name>
  <schema-version>0.0.11</schema-version>
    <short-name>computer</short-name>
  <namespace>http://example.com/ns/computer</namespace>
  <json-base-uri>http://example.com/ns/computer</json-base-uri>
  <define-assembly name="property">
    <formal-name>Computer Property</formal-name>
    <description>A property is a key-value pair of metadata about the computer, not its parts.</description>
    <define-flag name="key" as-type="token" required="yes"/>
    <define-flag name="value" as-type="string" required="yes"/>
    <define-flag name="ns" as-type="uri" required="yes" default="http://example-consortium.org"/>
    <constraint>
      <allowed-values  target=".[@ns='http://example-consortium.org' and @key='release-status']/@value">
        <enum value="unknown"/>
        <enum value="not-applicable"/>
        <enum value="in-development"/>
        <enum value="public"/>
        <enum value="obsolete"/>
      </allowed-values>
      <matches target=".[@ns='http://example-consortium.org' and @key='release-date']/@value" datatype="date-with-timezone"/>
    </constraint>
  </define-assembly>
  <define-assembly name="vendor">
    <formal-name>Vendor Information</formal-name>
    <description>Information about a vendor of a computer part.</description>
    <define-flag name="id" as-type="string" required="yes">
      <formal-name>Vendor Identifier</formal-name>
      <description>An identifier for classifying a unique computer parts vendor.</description>
    </define-flag>
    <model>
      <define-field name="name" min-occurs="1" max-occurs="1">
        <formal-name>Vendor Name</formal-name>
        <description>The registered company name of the vendor.</description>
      </define-field>
      <define-field name="address" min-occurs="1" max-occurs="1">
        <formal-name>Vendor Address</formal-name>
        <description>The physical address of an office location for the vendor.</description>
      </define-field>
      <define-field name="website" as-type="uri" min-occurs="1" max-occurs="1">
        <formal-name>Vendor Website</formal-name>
        <description>A public website made by the vendor documenting their parts as used in the computer.</description>
      </define-field>
    </model>
  </define-assembly>
  <define-field name="product-name" as-type="string">
    <formal-name>Product Name</formal-name>
    <description>The product name from the vendor of the computer part.</description>
  </define-field>
  <define-assembly name="firmware">
    <formal-name>CPU Firmware</formal-name>
    <description>Information about the firmware for a computer CPU.</description>
    <model>
      <define-field name="version" min-occurs="1" max-occurs="1" as-type="string">
        <formal-name>Firmware Version</formal-name>
        <description>An identifier that singles </description>
      </define-field>
      <define-field name="hash" min-occurs="1" max-occurs="1" as-type="string">
        <formal-name>Firmware Hash</formal-name>
        <description>A cryptographic hash with an approved algorithm of the firmware as flashed onto the chip.</description>
        <json-value-key>value</json-value-key>
        <define-flag name="algorithm">
          <formal-name>Hash Algorithm</formal-name>
          <constraint>
            <allowed-values>
              <enum value="sha256">The SHA-256 algorithm.</enum>
              <enum value="sha512">The SHA-512 algorithm.</enum>
            </allowed-values>
          </constraint>
        </define-flag>
        <constraint>
          <matches target=".[@algorithm='sha256']" regex="^[0-9a-fA-F]{64}$"/>
          <matches target=".[@algorithm='sha512']" regex="^[0-9a-fA-F]{128}$"/>
        </constraint>
      </define-field>
    </model>
  </define-assembly>
  <define-assembly name="computer">
    <formal-name>Computer Assembly</formal-name>
    <description>A container object for a computer, its parts, and its sub-parts.</description>
    <root-name>computer</root-name>
    <define-flag name="id" as-type="string" required="yes">
        <formal-name>Computer Identifier</formal-name>
        <description>An identifier for classifying a unique make and model of computer.</description>
    </define-flag>
    <model>
      <assembly ref="property" min-occurs="0" max-occurs="unbounded">
        <group-as name="properties" in-json="ARRAY" />
      </assembly>
      <assembly ref="vendor"/>
      <define-assembly name="motherboard">
        <formal-name>Motherboard Assembly</formal-name>
        <description>A container object for a motherboard in a computer and its sub-parts.</description>
        <model>
          <assembly ref="vendor"/>
          <define-field name="type" as-type="string" min-occurs="1" max-occurs="1">
            <formal-name>Motherboard Type</formal-name>
            <description>The type motherboard layout, <code>at</code>, <code>atx</code>, <code>mini-itx</code> or an alternative.</description>
          </define-field>
          <define-assembly name="cpu">
            <formal-name>Motherboard Central Processing Unit (CPU)</formal-name>
            <description>The model number of the CPU on the motherboard of a computer.</description>
            <model>
              <assembly ref="vendor"/>
              <field ref="product-name" min-occurs="1" max-occurs="1"/>
              <assembly ref="firmware"/>
              <define-field name="architecture" as-type="string" min-occurs="1" max-occurs="1">
                <formal-name>CPU Architecture</formal-name>
                <description>The Instruction Set Architecture (ISA) approved by module stakeholders.</description>
                <constraint>
                    <allowed-values target="." allow-other="no">
                        <enum value="amd64">Intel 64-bit systems, also known as x86-64 or em64t</enum>
                        <enum value="armhf">Arm v7 32-bit systems</enum>
                        <enum value="arm64">Arm v8 64-bit systems</enum>
                        <enum value="x86">Intel 32-bit x86 systems, for 686 class or newer</enum>
                    </allowed-values>
                </constraint>
              </define-field>
              <define-field name="speed" as-type="string" min-occurs="1" max-occurs="1">
                <formal-name>CPU Speed</formal-name>
                <description>The clock speed of the CPU in megahertz or gigahertz.</description>
              </define-field>
            </model>
          </define-assembly>
          <define-assembly name="ata-socket">
            <formal-name>Motherboard Advanced Technology Attachment (ATA) Socket</formal-name>
            <description>The model number of ATA socket on the motherboard of a computer. There will only be one socket on any motherboard.</description>
            <model>
              <define-assembly name="vendor">
                <formal-name>Vendor Information</formal-name>
                <description>Information about a vendor of a computer part.</description>
                <define-flag name="id" as-type="string" required="yes">
                  <formal-name>Vendor Identifier</formal-name>
                  <description>An identifier for classifying a unique computer parts vendor.</description>
                </define-flag>
                <model>
                  <define-field name="name" min-occurs="1" max-occurs="1">
                    <formal-name>Vendor Name</formal-name>
                    <description>The registered company name of the vendor.</description>
                  </define-field>
                  <define-field name="address" min-occurs="1" max-occurs="1">
                    <formal-name>Vendor Address</formal-name>
                    <description>The physical address of an office location for the vendor.</description>
                  </define-field>
                  <define-field name="website" as-type="uri" min-occurs="1" max-occurs="1">
                    <formal-name>Vendor Website</formal-name>
                    <description>A public website made by the vendor documenting their parts as used in the computer.</description>
                  </define-field>
                </model>
              </define-assembly>              
              <define-field name="product-name" as-type="string" min-occurs="1" max-occurs="1">
                <formal-name>Product Name</formal-name>
                <description>The product name from the vendor of the computer part.</description>
              </define-field>
              <define-field name="type" as-type="string" min-occurs="1" max-occurs="1">
                <formal-name>ATA Socket Type</formal-name>
                <description>The type of ATA socket on the motherboard with approved (but optional) values recommended by model stakeholders.</description>
                <constraint>
                  <allowed-values target="." allow-other="yes">
                    <enum value="pata">Parallel ATA buses also known as AT-Attachment and IDE</enum>
                    <enum value="sata">Serial ATA buses supporting Advanced Host Controller Interface or legacy IDE modes</enum>
                    <enum value="esata">External Serial ATA buses for pluggable external devices using SATA</enum>
                    <enum value="esatap">External Serial ATA buses supporting SATA traffic and device power</enum>
                  </allowed-values>
                </constraint>
              </define-field>
            </model>
          </define-assembly>
          <define-assembly name="memory" min-occurs="1" max-occurs="unbounded">
            <formal-name>Motherboard Random Access Memory (RAM) Module(s)</formal-name>
            <description>Random access memory hardware installed on the motherboard of a computer.</description>
            <group-as name="memory-modules" in-json="ARRAY"/>
            <model>
              <define-assembly name="vendor">
                <formal-name>Vendor Information</formal-name>
                <description>Information about a vendor of a computer part.</description>
                <define-flag name="id" as-type="string" required="yes">
                  <formal-name>Vendor Identifier</formal-name>
                  <description>An identifier for classifying a unique computer parts vendor.</description>
                </define-flag>
                <model>
                  <define-field name="name" min-occurs="1" max-occurs="1">
                    <formal-name>Vendor Name</formal-name>
                    <description>The registered company name of the vendor.</description>
                  </define-field>
                  <define-field name="address" min-occurs="1" max-occurs="1">
                    <formal-name>Vendor Address</formal-name>
                    <description>The physical address of an office location for the vendor.</description>
                  </define-field>
                  <define-field name="website" as-type="uri" min-occurs="1" max-occurs="1">
                    <formal-name>Vendor Website</formal-name>
                    <description>A public website made by the vendor documenting their parts as used in the computer.</description>
                  </define-field>
                </model>
              </define-assembly>
              <define-field name="product-name" as-type="string" min-occurs="1" max-occurs="1">
                <formal-name>Product Name</formal-name>
                <description>The product name from the vendor of the computer part.</description>
              </define-field>
              <choice>
                <define-field name="byte-size" as-type="positive-integer" min-occurs="1" max-occurs="1" deprecated="0.0.9">
                  <formal-name>Memory Module Size</formal-name>
                  <description>Size of the memory module in binary, not SI base-10 units, meaning a kilobyte is 1024 bytes, not 1000 bytes.</description>
                </define-field>                
                <define-field name="size" as-type="positive-integer" min-occurs="1" max-occurs="1">
                  <formal-name>Memory Module Size</formal-name>
                  <description>Size of memory module in binary or SI base-10 units, optionally with a size unit. This does not require to be in bits or bytes. If no optional flags are used, it is required to process its value as a size as counted in bits (not bytes) in decimal base-ten form, with no unit prefix.</description>
                  <json-value-key>count</json-value-key>
                  <define-flag name="unit" required="no">
                    <formal-name>Memory Module Size Unit</formal-name>
                    <description>The unit size for a memory module can either be bytes (B) or bits (b).</description>
                    <constraint>
                      <allowed-values allow-other="no">
                        <enum value="B">bytes</enum>
                        <enum value="b">bits</enum>
                      </allowed-values>
                    </constraint>
                  </define-flag>
                  <define-flag name="base" required="no">
                    <formal-name>Memory Module Size Unit Prefix Base</formal-name>
                    <description>The prefix type of module size, binary or decimal. This is useful if you will not specify an optional unit or unit base.</description>
                    <constraint>
                      <allowed-values allow-other="no">
                        <enum value="binary"/>
                        <enum value="decimal"/>
                      </allowed-values>
                    </constraint>
                  </define-flag>
                  <define-flag name="prefix" required="no">
                    <formal-name>Memory Module Size Unit Prefix</formal-name>
                    <description>The optional prefix the of unit from a given system.</description>
                    <constraint>
                      <allowed-values allow-other="yes">
                        <enum value="Gi"/>
                        <enum value="Ki"/>
                        <enum value="Mi"/>
                        <enum value="G"/>
                        <enum value="k"/>
                        <enum value="M"/>
                      </allowed-values>
                    </constraint>
                  </define-flag>
                  <define-flag name="unit-system">
                    <formal-name>Memory Module Size Unit System</formal-name>
                    <description>An identifier for the organization associated with the specific usage of the unit with its prefix. If absent, the use of no unit is assumed with and the value is counted in bits.</description>
                    <constraint>
                      <allowed-values allow-other="yes">
                        <enum value="iec">The  International Electrotechnical Commission 60027-2 Amendment 2 Units</enum>
                        <enum value="jedec">JEDEC Solid State Technology Association Units</enum>
                        <enum value="si">International System of Units</enum>
                      </allowed-values>
                    </constraint>
                  </define-flag>
                </define-field>
            </choice>
            </model>
            <constraint>
              <expect id="memory-divisible-two" level="ERROR" target="./byte-size" test="(. mod 2) = 0">
                  <message>All memory modules MUST have a byte divisible by two.</message>
              </expect>
              <expect id="memory-divisible-megabyte" level="WARNING" target="./byte-size" test="(. mod 1024) = 0">
                  <message>All memory modules SHOULD have a bite size divisible by one megabyte (1,024 bytes) .</message>
              </expect>
              <expect id="memory-byte-size-deprecated" level="WARNING" target="." test="count(./byte-size) = 0">
                <message>All memory modules SHOULD use size because byte-size is now deprecated and byte-size will be removed.</message>
              </expect>
            </constraint>
          </define-assembly>
          <define-assembly name="expansion-card" min-occurs="0" max-occurs="unbounded">
            <formal-name>Motherboard Expansion Card</formal-name>
            <description>The model number of an expansion card connected to the motherboard of a computer.</description>
            <group-as name="expansion-cards" in-json="ARRAY"/>
            <model>
              <define-assembly name="vendor">
                <formal-name>Vendor Information</formal-name>
                <description>Information about a vendor of a computer part.</description>
                <define-flag name="id" as-type="string" required="yes">
                  <formal-name>Vendor Identifier</formal-name>
                  <description>An identifier for classifying a unique computer parts vendor.</description>
                </define-flag>
                <model>
                  <define-field name="name" min-occurs="1" max-occurs="1">
                    <formal-name>Vendor Name</formal-name>
                    <description>The registered company name of the vendor.</description>
                  </define-field>
                  <define-field name="address" min-occurs="1" max-occurs="1">
                    <formal-name>Vendor Address</formal-name>
                    <description>The physical address of an office location for the vendor.</description>
                  </define-field>
                  <define-field name="website" as-type="uri" min-occurs="1" max-occurs="1">
                    <formal-name>Vendor Website</formal-name>
                    <description>A public website made by the vendor documenting their parts as used in the computer.</description>
                  </define-field>
                </model>
              </define-assembly>
              <define-field name="product-name" as-type="string" min-occurs="1" max-occurs="1">
                <formal-name>Product Name</formal-name>
                <description>The product name from the vendor of the computer part.</description>
              </define-field>
              <define-field name="type" as-type="string" min-occurs="1" max-occurs="1">
                <formal-name>Expansion Card Type</formal-name>
                <description>The type of expansion card on a motherboard of a computer, such as <code>pci</code> (PCI, e.g. Peripheral Component Interconnect), <code>pcie</code> (PCI Express), or an alternative.</description>
              </define-field>
            </model>
          </define-assembly>
        </model>
        <constraint>
          <expect id="memory-same-byte-size" level="ERROR" target="." test="if (count(./memory/byte-size) > 0) then (sum(./memory/byte-size) mod ./memory/byte-size[1]) = 0 else (sum(./memory/size) mod ./memory/size[1]) = 0">
              <message>All memory modules SHOULD be the same size or byte-size for a computer.</message>
          </expect>
          <has-cardinality id="atx-memory-count-allowed" level="ERROR" target="motherboard[@type='atx']/memory" min-occurs="1" max-occurs="4"/>
          <has-cardinality id="atx-ata-sockets-count-allowed" level="ERROR" target="motherboard[@type='atx']/ata-socket" min-occurs="1" max-occurs="4"/>
          <has-cardinality id="mini-itx-memory-count-allowed" level="ERROR" target="motherboard[@type='atx']/memory" min-occurs="1" max-occurs="2"/>
          <has-cardinality id="mini-itx-ata-sockets-count-allowed" level="ERROR" target="motherboard[@type='atx']/ata-socket" min-occurs="0" max-occurs="0"/>
        </constraint>
      </define-assembly>
    </model>
  </define-assembly>
</METASCHEMA>
{
  "computer": {
    "id": "awesomepc1",
    "properties": [
      {
        "ns": "http://example-consortium.org",
        "key": "release-status",
        "value": "public"
      },
      {
        "ns": "http://specific-vendor.com",
        "key": "release-status",
        "value": "custom"
      },      
      {
        "ns": "http://example-consortium.org",
        "key": "release-date",
        "value": "2024-01-0Z"
      }
    ],
    "motherboard": {
      "vendor": {
        "id": "vendor2",
        "name": "ISA Corp",
        "address": "2000 K Street NW Washington, DC 20002",
        "website": "https://example.com/isacorp/"
      },
      "type": "atx",
      "cpu": {
        "vendor": {
          "id": "vendor2",
          "name": "ISA Corp",
          "address": "2000 K Street NW Washington, DC 20002",
          "website": "https://example.com/isacorp/"
        },
        "product-name": "Superchip Model 1 4-core Processor",
        "firmware": {
          "version": "1.2.1",
          "hash": {
            "algorithm": "sha512",
            "value": "7e9c54ef590b3e053495c253e135695eb55f4e966d49671e8739f5574d27f7809fefb8f75b998b1333a934bb59f4246928c11621e411286d77191a53ae362e3a"
          }
        },
        "architecture": "arm64",
        "speed": "4.7 gigahertz"
      },
      "ata-socket": {
        "vendor": {
          "id": "vendor2",
          "name": "ISA Corp",
          "address": "2000 K Street NW Washington, DC 20002",
          "website": "https://example.com/isacorp/"
        },    
        "product-name": "AwesomeSAS Model 1 Storage Socket",
        "type": "sas"
      },
      "memory-modules": [
        {
          "vendor": {
            "id": "vendor3",
            "name": "Massive Memory Corp",
            "address": "3000 K Street NW Washington, DC 20003",
            "website": "https://example.com/massive-memory-corp/"
          },
          "product-name": "Erroneous Model 3 DDR4-3200 8GB (Module 1)",
          "size": {
            "count": 7,
            "prefix": "G",
            "unit": "B",
            "unit-system": "si",
            "base": "decimal"
          }
        },
        {
          "vendor": {
            "id": "vendor3",
            "name": "Massive Memory Corp",
            "address": "3000 K Street NW Washington, DC 20003",
            "website": "https://example.com/massive-memory-corp/"
          },
          "product-name": "Model 3 DDR4-3200 8GB (Module 2)",
          "size": {
            "count": 7,
            "prefix": "G",
            "unit": "B",
            "unit-system": "si",
            "base": "decimal"         
          }
        }
      ]
    }
  }
}

Current source from WIP draft here

I do agree the above example is more contrived but there is a progression outlined in this tutorial, based on what I inferred from OSCAL before we wrote the spec for this constraint in usnistgov/metaschema#547, to document what was less clear than before. So I am just pointing out logically, the @target/@test mechanism and how you can have rules adjacently meet different criteria (with expect), regardless of how you name them, as you get up the ladder of understanding these, makes sense to me. As-is, discovering how has-cardinality work without @test or whatever you decide to call it makes this incongruous with the others.

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aj-stein-nist commented Mar 1, 2024

Also of note: here is a sample that passes the test as given, which is actually not self-contradictory

Excellent point and I didn't even cover this in the issue or my example. You can make more elaborate use of @target or another equivalent to @test if that existed to make sure it is of only that kind or fail.

Regarding expect and how all of them are designed, we could replace everything with <expect/>. However, that leads to some very clunky Metapath (for model developers to write or for upstream Metaschema processors to implement out the gate) for realistic use. At that point, I would argue <allowed-values/> or <index/> could go, but the progression ladder allows more junior people to have expressive power for simpler use cases without writing up advanced Metapath.

Now regarding this progression of difficulty with Metapath and this decision, maybe we can talk about that here or in the issue: is that a hard requirement or just a nice to have? It seems almost of the constraint system is designed for it to be more than a nice to have, and it is a hard requirement to make easier use cases easier for model developers to use at the expense of (understandably) harder to implement for the processor devs, but this point is not lost on me.

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