Handling startPostition in CSW getRecords

[etj]

When startPosition exceeds the number of matched records, GeoNetwork returns an exception:

<ows:ExceptionReport xmlns:ows="http://www.opengis.net/ows" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" version="1.2.0" xsi:schemaLocation="http://www.opengis.net/ows http://schemas.opengis.net/ows/1.0.0/owsExceptionReport.xsd">
  <ows:Exception exceptionCode="InvalidParameterValue" locator="startPosition">
    <ows:ExceptionText>Start position (1212) can't be greater than number of matching records (158 for current search).</ows:ExceptionText>
  </ows:Exception>
</ows:ExceptionReport>

[etj]

In OGC CSW (Catalog Service for the Web), when handling a GetRecords request, the startPosition parameter specifies the index of the first record to return in the result set. The indexing is 1-based (meaning the first record is at position 1).

According to the CSW specification (OGC 07-006r1 - CSW 2.0.2):

If the startPosition is greater than the total number of matched records, the server must return an empty SearchResults element, but the response is still valid.

The response should correctly indicate:

• The numberOfRecordsMatched (total number of records that match the query).
• The numberOfRecordsReturned (which would be 0 in this case).
• The nextRecord value, which typically would be 0 to indicate there are no more records.

It would not be correct to return an exception in the case where the startPosition exceeds the number of matched records in an OGC CSW GetRecords request.

Why?

The OGC CSW 2.0.2 specification (OGC 07-006r1) clearly indicates that this is not considered an error condition.
Instead, it is treated as a valid query that simply returns zero results.

Supporting points:

• Clause 10.8.5 (SearchResults Element) describes that:

  "If fewer records are available than the requested number starting from the specified start position, 
  then the number of  records returned will be less than the requested number and may be zero."
  

• The spec never mentions that a startPosition beyond the number of matched records should trigger an exception.

• Exception reporting (Section 10.11, Table 24: Exception Codes) defines specific cases where exceptions should be returned (e.g., invalid parameters, unsupported output schemas, etc.). Out-of-range pagination is not among them.

Expected Correct Behavior:

Return a valid SearchResults response with:

• numberOfRecordsMatched = total matched records
• numberOfRecordsReturned = 0
• nextRecord = 0

Summary:

Situation	Recommended Response
startPosition > numberOfRecordsMatched	✅ Return an empty but valid response (no exception)
Invalid parameter names, unsupported types, schema errors	❌ Return an exception

Final answer

No, returning an exception in this case is not compliant with the CSW specification. You must return a valid response with zero records instead.