View source for 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.