FORMATS / IDENTIFIERS / METHODS
Documentary reference library
Find an identifier, unit, HTTP status or data convention, then open the method explaining its use and limits.
193 references · page 7 of 9
| Object to check | Code or notation | Context and use |
|---|---|---|
| Area: convert m², hectares and km² without losing decimals | 1 km² · 1 ha · 1 km² · 2.5 ha | Changing an area unit does not change the territory measured. A kilometre is one thousand metres, so a square kilometre contains one thousand times one thousand square metres. The table and converter make that square explicit. |
| World Bank API: distinguish three dates and recover the unit | date · lastupdated · extracted · unit · decimal / value · pages / total | A JSON response contains more than a value. The real excerpt below concerns Finnish density in 2023. Its header reports a WDI update on 8 October 2026; this snapshot was retrieved on 23 October. Those three dates answer different questions. |
| Autofill: read tokens in the right order | section-* · shipping | billing · home | work | mobile | fax | pager · name | postal-code | email | … · webauthn · on | off | Two addresses in one form can require different values even when the fields have the same name. autocomplete describes a purpose and a field group; it replaces neither the visible label nor validation. These examples illustrate HTML grammar, not collected identities or contact details. |
| Form parameters: preserve spaces, plus signs and duplicate names | U+0020 · + · & · = · été · append / get / getAll / set | A parameter list is an ordered sequence of name-value pairs. The same name may occur twice. This tool applies application/x-www-form-urlencoded through URLSearchParams to two single-line values, then parses the result; it submits no form. |
| Form field: separate label, help, constraint and error | label[for] / id · placeholder / aria-describedby · type / inputmode · pattern · required / aria-required · aria-invalid / error text · WCAG 3.3.1 / 3.3.3 · client / server | For a postal code, 00123 can be a string to preserve rather than a quantity to add. Control choice follows the intended meaning. This table gives separate checks for a form review; no single attribute proves that an application is valid or that the whole journey conforms. |
| Text contrast: compare the ratio before rounding | ratio · WCAG 1.4.3 · AA · WCAG 1.4.3 · AA · large · WCAG 1.4.6 · AAA · 4.499:1 | Different colours can still be difficult to distinguish. WCAG 2.2 compares their relative luminances after linearising the sRGB components. This tool calculates that ratio for two opaque colours; it does not sample pixels from a photograph. |
| CSS framing: measure what cover clips and contain leaves empty | contain · cover · rendered · object-position · fill ≠ cover | The same thumbnail box can show different parts of an image depending on its fit. Both modes preserve aspect ratio but satisfy opposite constraints. This explorer calculates a centred geometric model from already oriented dimensions. |
| Exif orientation: eight arrangements, not just four rotations | 1 · 2 · 3 · 4 · 5 · 6 · 7 · 8 | The Orientation tag, identifier 274 (0x0112), specifies where the first row and first column of encoded data appear on the display. Some values require mirroring. The diagrams reuse one asymmetric shape and four corners marked A, B, C and D; they do not depict an edited photograph. |
| Volume and throughput: state the units before estimating a transfer | 1 B · 1 MB · 1 MiB · 1 GB / 1 GiB · t | The same number describes different volumes in GB and GiB. To prepare migration or recovery, first convert the size to bytes and throughput to bits per second. The calculator then gives an arithmetic duration at constant throughput, not a network measurement. |
| Recovery: connect RPO, RTO and business-process interruption | RPO · Δdata · RTO · MTD · Δprocess ≥ Δresource | An exercise may recover recent files yet restore service too late. It may also restore service quickly using data that is too old. This reader compares three distinct measurements against three user-entered objectives; its numbers are teaching examples, not commitments by this site. |
| Recovery exercise: connect each conclusion to evidence | snapshot · data · integrity · access · function · dependencies · decision | A successful copy log, a matching digest and a usable application answer different questions. This table adapts the NIST guide’s data and functionality validation stages to a multilingual website. It describes evidence to produce during an exercise; it does not claim those tests were performed on your hosting. |
| ORCID: check the digit without assigning an identity | body · MOD 11-2 · X · URI · scope | An ORCID retains leading zeros and encodes neither country, institution nor discipline. Its last position checks transcription. The examples below are published by ORCID; they are not identities that a reader may claim. |
| ROR: decode the checksum without inferring an organisation | pattern · alphabet · 2mhbdp · check · record | A ROR identifier is a random string with no information about the institution or its relationships. Its preferred form is a full URL. The documentation uses 02mhbdp94 as an example; this reader exposes the conversion before checking the digits. |
| LEI: separate format, modulo-97 remainder and digit warning | pattern · A → Z · check · body + 00 · warning | A LEI may contain twenty characters yet fail the transcription check. The XBRL taxonomy also distinguishes an arithmetic error from a warning about certain endings. The example uses the LEI displayed by GLEIF for the foundation itself without inferring its current status. |
| Repeated keys: predict row counts before joining | nL = 2 · nR = 2 · LEFT · FULL · NULL component · composite key | An identifier appearing in both tables does not guarantee a one-to-one relationship. Each key’s frequencies determine the number of pairs. The teaching example uses two-string composite keys; FR and FI are markers only, not references to real records. |
| Excluding rows: NOT IN and NOT EXISTS can differ | "B" IN ("A", NULL) · "A" NOT IN ("A", NULL) · empty subquery · NOT EXISTS · = · NOT EXISTS · IS NOT DISTINCT FROM | Finding keys absent from a second table requires a policy for missing values. A NULL in a subquery result can make NOT IN unknown. These expressions concern one column; the reader also distinguishes an equality that explicitly treats NULL values as comparable. |
| Timestamps: check the calendar before comparing strings | Gregorian · UTC · RFC 9557 §2 · fraction · ordering | Different spellings can represent the same instant. Conversely, alphabetical order can contradict time order when offsets or fractions differ. The comparator retains the input text and calculates within an explicit profile without asking the browser to infer a time zone. |
| Time windows: state the bounds to prevent double counting | [a,b) · [a,b) ∩ [b,c) · intersection · [a,a) · PostgreSQL 18 | The [start, end) convention includes the start and excludes the end. Two windows can meet without assigning their shared boundary instant to both. An extraction must state this choice; it does not automatically make an API’s filters exclusive. |
| Connectivity: distinguish people, fixed subscriptions and mobile lines | IT.NET.USER.ZS · IT.NET.BBND.P2 · IT.CEL.SETS.P2 · SP.POP.TOTL | The extract covers 2021–2023 for France, Finland, Brazil and India. It contains 36 telecommunications observations and 12 reference populations. These four countries illustrate definitions and methods without forming a ranking or a representative global sample. |
| Choose a digital measure for the question being asked | Internet use · Fixed subscriptions · Voice cellular subscriptions · Households / speed / AI | Similar names do not make indicators interchangeable. The selector compares six questions with the extract’s three telecommunications series. It also identifies questions none of them answers, to avoid turning subscriptions into a measure of equipment or behaviour. |
| Four countries: see what population weighting changes | Equal weights · WDI population weights · Σ population · 2023 · Difference | For the four selected countries in 2023, the simple mean of Internet-use shares is 81.188278%. The scenario using WDI populations as weights gives 64.343169%. Both are calculated here from published values, not copied from an official ITU or World Bank aggregate. |
| Top results: separate precision, recall and first success | Corpus · P@k / Recall@k · RR@k · AP@k · R denominator | Two rankings may retrieve the same number of relevant documents while placing them at very different positions. This exercise separates quality within the first k results, coverage of the collection and the wait for the first useful result. |
| NDCG: state the gain and build the right ideal ranking | gain(g) · discount(i) · IDCG@k · NDCG@k | Grades 1, 2 and 3 do not yet specify how relevance is valued. Compare linear and exponential gains on the same documents; the ideal ranking must come from the full collection at the same k. |
| Incomplete judgments: preserve unknowns and scope | Judged / retrieved · P@5 bounds · P among judged · Recall · collection | Relevance is assessed for a particular information need. A partially judged collection does not make unjudged documents useless. This separate example distinguishes judgment coverage, observed precision and possible bounds. |
From format to fact: three separate checks
Recognise the format
An identifier matching a pattern or checksum can still refer to the wrong entity. A format check catches typing errors; it does not verify the holder.
Find the right object
Open the corresponding register or document. Compare its name, scope, version and period with your question. Retain technical identifiers without translating them.
Qualify the conclusion
Separate what the source declares, what you observed and what remains unestablished. A value without a unit, period or definition cannot support a reliable comparison.
Notation examples explain a rule. They are neither certification nor a live check of your dossier.
Check documentary identifiers