25.13. Structural metadata items for international merchandise trade statistics. The following are typical structural metadata items that belong to the trade values and quantities in each international merchandise trade statistics dataset (see IMTS 2010, para. 9.23):
(a) Reporting country: identification of the country that reported the given data set;
(b) Reference period: identification of the specific month, quarter, year, etc.;
(c) Trade flow: whether the data refer to exports, imports, re-exports, etc.;
(d) Commodity code: identification of the commodity or commodity group;
(e) Commodity description: stand-alone descriptors of the commodity codes at any level of aggregation;
(f) Commodity classification: name of the classification used to report the data (e.g., HS2007, SITC Rev. 4, national classification, etc.);
(g) Partner country or region: identification of the partner country or region;
(h) Country or region classification (e.g., alpha-2 or alpha-3 ISO country codes; United Nations standard country or area codes for statistical use, etc.), including information on the country-composition of geographical regions;
(i) Currency unit: identification of the currency unit (e.g., national currency,United States dollars, etc.) in which trade values are expressed;
(j) Mode of transport;
(k) Weight unit: identification of the weight unit in which trade quantity data (net weight data) are expressed;
(l) Supplementary quantity unit: identification of the unit of measurement, by HS code, in which supplementary trade quantity data are expressed;
(m) Valuation: identification of whether trade values are expressed in FOB or CIF terms;
(n) Custom procedure code (or applicable transaction code).
25.14. Reference metadata items for international merchandise trade statistics. The following items are typically part of the reference metadata associated with international merchandise trade statistics (see IMTS 2010, para. 9.23):
(a) Legal framework and institutional arrangements (e.g., references to relevant laws and regulations, role of all institutions involved in compilation, etc.);
(b) Underlying concepts and definitions (e.g., definition of statistical territory and trade system used, definition of statistical value, scope of international merchandise trade statistic and their relationship to national accounts and balance-of-payments statistics, etc.);
(c) Description of data sources used and methodology of data integration (e.g., customs declarations and related customs records, non-customs administrative sources, enterprise surveys, and a brief description of how data obtained from these sources are merged to create an integrated data set);
(d) Description of data-collection and data-processing procedures (e.g., frequency of data collection, description of specific procedures used for data collection, validation, editing, aggregation, etc.);
(e) Estimation methods (e.g., estimation of value of trade below customs and statistical thresholds, CIF-FOB adjustments, estimation of quantities, etc.);
(f) Dissemination policy (e.g., release and revision schedules);
(g) Additional explanations and footnotes concerning the data, as required (e.g., explanatory notes on revisions, breaks in series, application of confidentiality rules, treatment of special categories of goods, etc.);
(h) Quality reporting.
 The Harmonized System (HS) often does not provide stand-alone descriptors of individual commodity codes, as the titles of the HS headings and subheadings often do not describe their scope (inasmuch as they use, e.g., such titles as “others”), and/or refer to other headings and subheadings as well as to sections, chapters or headings notes. While not as precise as the legal text, standalone descriptors provide an easily accessible and concise indication of the scope of the HS codes.
 Available from http://unstats.un.org/unsd/methods/m49/m49.htm.