Use Case 16: Preview Granule (metadata driven)

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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


Contents

[edit] 1.Use Case Identification

[edit] 1.1.Use Case Number

EIE16

[edit] 1.2.Use Case Name

Provide a standard preview of a data granule as referenced by an element in the granule metadata.

[edit] 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.

[edit] 2.1.Actors

User

[edit] 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.

[edit] 2.3.Postconditions

  • 1.The user is provided with a preview image

[edit] 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.

[edit] 2.5.Alternative Flows

[edit] Metadata do not contain preview URLs:

  • EIE16.1.1) Granules lacking preview URLs are listed without corresponding links.

[edit] 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.

[edit] 2.7.Extension Points

None

[edit] 2.8.Priority

High

[edit] 2.9.Frequency of Use

Invoked multiple times per session

[edit] 2.10.Business Rules

None

[edit] 2.11.Special Requirements

URLs corresponding with preview images must return a valid image file.

[edit] 2.12.Assumptions

None

[edit] 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.

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