INDUSTRY FIELD GUIDE
Secondary-market loan tape revisions for AI testing
Two loan tapes may represent different dates or corrections to the same date.
NAICS 522299 · International, Secondary Market, and All Other Nondepository Credit Intermediation
Two loan tapes may represent different dates or corrections to the same date. Combining them can double-count exposures. FHFA’s public use database illustrates public mortgage data and its documented fields. A secondary-market operator can make a mock inventory with intentionally different versions. FHFA public use database
Make two fictional snapshots with invented asset IDs and a correction file. Add one revision that changes the status of an existing row and one genuine new asset. Ask the assistant to reconstruct the snapshot as of a stated date and explain why a corrected record is not an additional loan. Have a reviewer confirm expected counts and visible changes before testing.
Do not copy borrower data, property or loan IDs, investor reports, pricing, or licensed loan tape data. Use clearly synthetic terms and no underwriting decisions.
Describe a snapshot reconciliation sample
Original Fiund exercise
A corrected snapshot row and a new asset affect counts differently
A synthetic inventory uses invented asset aliases and simple status labels. No borrower, property, actual loan term or licensed loan tape is present.
| Record | Source | What it records |
|---|---|---|
| LT1 | Snapshot P1 | As of day 10: asset A active, asset B pending. Snapshot count 2. |
| LT2 | P1 correction file | Explicitly replaces B's day-10 status with active. No new asset row; references LT1/B. |
| LT3 | Snapshot P2 | As of day 20: A active, B active, new asset C active. P2 is a later snapshot, not a correction to P1. |
Question for the model
Reconstruct the corrected day-10 inventory and compare its count with the day-20 inventory without double-counting versions.
Show the reference answer and checks
LT2 updates B's status within LT1's day-10 snapshot, leaving two assets, A and B, both active. It does not create a third asset. LT3's later day-20 snapshot adds distinct C, giving three assets for that date. Keep snapshots separate and apply the correction to its named parent rather than appending every row from all versions into one inventory. The fixture supplies no pricing or underwriting conclusion.
- Appending a corrected row as an additional exposure.
- Combining later snapshots with earlier ones and counting the same asset repeatedly.
Fields to preserve
- Snapshot date and parent
- Defines the inventory time.
- Asset alias and correction target
- Preserves stable identity.
- Status, replacement rule and distinct count
- Makes the reconstruction checkable.
Test another case
Add a correction for B dated day 20 with no snapshot-parent reference. Require a scope clarification before applying it to P1 or P2.
Use original invented rows. Exclude actual IDs, investor reports, pricing and borrower information; no credit decision belongs in the benchmark.
Discuss a contribution
Describe the sources you control, the task they could support and what has already been checked. Use the existing-data assessment for an archive or the collection brief for a new recording project. The contributor agreement defines Fiund’s licensing authority and compensation. A guide or fictional exercise does not establish an accepted collection or a sale.