View source for OpenSite/Concepts/Documents and identity

__NOTOC__
{{OpenSite scope}}
Use the right identity for the operation you are performing.

== Four identities ==
{| class="wikitable os-table"
! Value !! Purpose !! Lifetime
|-
| Persistent document ID || Identifies saved model content || Survives save/reopen
|-
| Session handle || Addresses an open document instance || Valid only for that live session
|-
| Object ID || Identifies an object inside a document || Retained by document persistence
|-
| Name and label || Unique lookup name and human-readable display label || Different from the object ID
|}

== Read identity explicitly ==
{{Code|lang=python|code=<nowiki>import opensite

doc = opensite.execute("document.new", {})["document"]
created = opensite.material_create_user(doc, {
    "name": "Practice steel", "family": "steel", "role": "structural_steel",
    "has_elastic": True, "elastic_pa": 210.0e9,
    "has_poisson": True, "poisson": 0.28,
    "has_mass_density": True, "mass_density": 7850.0,
    "has_thermal": True, "thermal_per_k": 1.2e-5,
})
item = doc.get_object(created["id"])
print("Persistent document:", doc.identity())
print("Session handle:", doc.session)
print("Object ID:", item.id)
print("Internal name:", item.name)
print("Display label:", item.label)
assert doc.get_object(item.name).id == item.id
opensite.material_renumber(doc, item.id, 12)
assert doc.get_object(item.id).id == item.id</nowiki>}}

== Transactions and files ==
An accepted edit publishes a consistent revision. Undo/redo are session history. Saving writes document data, not the undo stack. Reopening returns a new live handle; do not keep using a closed one.
[[File:OpenSite_Document_Flow.svg|850px|center]]

== Next lesson ==
[[OpenSite/Guides/First document|Practise edit, undo, redo, save and reopen.]]

<div class="os-page-nav">{{Docnav|OpenSite/Workspace tour|OpenSite/Concepts/Properties and units|OpenSite/Guides|All guides}}</div>
[[Category:OpenSite documentation]]