app identifier fields

Identifier fields are the columns a join actually runs on. In store data they take three forms in this catalog: Apple's numeric track IDs, Google Play's package names, and composite keys built from a store column plus a store_id, as exposed in the play-and-apple-app-store-metrics dataset's field set of store, store_id and app_name.

Their value is stability under churn. The apple-app-store-10k-apps-dataset records that its description file is keyed by the same 7,197 app ids, so descriptive text can be attached to metrics without fuzzy matching. Apple's iTunes Search API mirrors the discipline at query time: its /lookup endpoint returns one result per lookup ID, making ID-based retrieval deterministic where name search is not.

Identifiers are the backbone of the application-software slice, where most sources publish listing metadata rather than usage telemetry and the record count is the unit of sale.

Without stable IDs, every longitudinal claim is a matching exercise. Names change and duplicate listings abound: one cataloged App Store description file stays keyed by 7,197 app ids precisely because names could not be trusted to stay still.

• Joins fail loudly or silently. A name-based join usually 'works' and quietly mismatches renamed or regionalized listings; an ID-based join fails visibly when an ID is absent.
• Deduplication depends on key design. Composite store + store_id keys are what let a multi-store panel count an app once per store rather than twice overall.
• Vendor claims become testable. If a provider says two files cover the same apps, the shared ID space proves or disproves it in one query.

Use these checks to test whether a source delivers what the concept promises:

1. Confirm raw store IDs ship, not just names. Apple track IDs and Google Play package names should appear as their own columns, as in the store/store_id/app_name layout.

1. Test a cross-file join on IDs alone. The App Store description file keyed by 7,197 app ids should merge cleanly onto any metrics file claiming the same universe.

1. Validate with a lookup round-trip. iTunes Search's /lookup endpoint returns one result per lookup ID - resolve a sample of IDs and compare against your file.

1. Watch for composite-key drift. When stores are combined, insist on store + store_id rather than store_id alone, since ID namespaces differ per store.

Where to see it in context: application-software data.

The companion concept and where these fields occur:

• app-metadata