Use Case 16: Preview Granule (metadata driven)
Use Case EIE16: Preview Granule (Metadata driven)
for
ESIP Earth Information Exchange
Version 1.0 draft
Prepared by Karl Benedict
Earth Data Analysis Center, University of New Mexico
November 22, 2005
1.Use Case Identification
1.1.Use Case Number
EIE16
1.2.Use Case Name
Provide a standard preview of a data granule as referenced by an element in the granule metadata.
2.Use Case Definition
This use case represents a need to provide system users a preview of a data granule that they are considering for use or download. This preview would be encoded into the metadata for the granule, and be accessible via a simple URL. The preview may be generated by a service or represented by a static image file (browser supported) accessible via the URL, but access should be via a simple URL request.
2.1.Actors
User
2.2.Preconditions
- 1.User has been presented with a list of granules (Use case EIE09)
- 2.If the metadata for a listed granule provides a preview URL, a link to that URL will be included in the granule listing.
2.3.Postconditions
- 1.The user is provided with a preview image
2.4.Normal Flow
- EIE16.0.1) When a list of granules is generated as a result of a granule listing, available preview URLs are read from the metadata records
- EIE16.0.2) Preview links are added to the listing of granules, as available.
2.5.Alternative Flows
Metadata do not contain preview URLs:
- EIE16.1.1) Granules lacking preview URLs are listed without corresponding links.
2.6.Exceptions
Preview file returned by URL is not a valid image file. Display an error message to the user and log the error.
2.7.Extension Points
None
2.8.Priority
High
2.9.Frequency of Use
Invoked multiple times per session
2.10.Business Rules
None
2.11.Special Requirements
URLs corresponding with preview images must return a valid image file.
2.12.Assumptions
None
2.13.Notes and Issues
Recommendations regarding performance requirements and file sizes should be produced to provide a reasonable system response when providing preview images. Computationally intensive 'live' previews might be discouraged.
