Store 7.x cannonical URL for resource migrated to CLAW

[mjordan]

Title (Goal)	Store 7.x cannonical URL for resource migrated to CLAW
Primary Actor	Repository admin
Scope	Specific service
Level	High
Story	As a repository admin migrating content from 7.x to CLAW, I want to be able to store each 7.x object's URL as a property of the migrated object. In other words, for each newly migrated object in CLAW, I want to be able to access its previous address on the web.

[mjordan]

Some possible uses I would put this stored URL to:

• I want my users to be automatically redirected from the old /islandora/object/foo:bar-style URLs to the corresponding new /node/baz-style URLs.
• To ensure continuity of PREMIS events across the migration, I want to be able to assemble all the fixity validation events for a given datastream/binary resource that was migrated from 7.x to CLAW.
• To collect usage statistics across the period when the migration occurred, I want to be able to aggregate usage for a resource in CLAW with its version in 7.x.

[mjordan]

During our migration from CONTENTdm to Islandora, we added the previous URL to our MODS like this:

<identifier type="uri" invalid="yes" displayLabel="Migrated From">http://content.lib.sfu.ca/cdm/ref/collection/foo/id/14</identifier>

and used those URLs to provide auto-redirection.

[mjordan]

@dannylamb can we include this in the sprint?

[dannylamb]

@mjordan It will definitely get handled then. That plus a /islandora/object/{pid} url alias with pathauto. I've been very careful not to use that route so that it's available for people who want to keep urls when migrating.

[mjordan]

Nice. Funny you should mention creating a path alias, I am doing this to keep the old URLs from our IR during our migration to Islandora 7.x in a hook_islandora_object_ingested:

/**
 * Inserts a path alias.
 *
 * @param string $pid
 *   A PID.
 * @param string $old_nid
 *   The item's old Summit node ID.
 */
function islandora_summit_migration_insert_path_alias($pid, $old_nid) {
  return db_insert('url_alias')
    ->fields(array('source' => 'islandora/object/' . $pid, 'alias' => 'item/' . $old_nid, 'language' => 'und'))
    ->execute();
}

[mjordan]

A module that creates the alias is at https://github.com/mjordan/islandora_pid_alias.