The Problem of on-and off existence
Goths's Lodge Item:Q10575 is a typical example: it has a starting point Property:P49 but actually several new starts and more than one end Property:P50. People found a lodge, the lodge is closed (in the events of the French Revolution), it re-opens in the national wave of the Napoleonic wars, it is closed again in 1935 and re-eopened in 1949 or later or never.
Is it always the same lodge? What do we do with changing names? The German National Library creates loads of items under ever new names - and you have to make sure to get the respective successions. The alternative: If those involved wanted to state that they actually are the same people (even if that is only a fiction of continuity) let them:
See Item:Q10575 Lodge "Ernst zum Compaß", Gotha
We can now use qualifiers on each active phase in order to state a respective beginning and a respective end. Is this a good option? How does it work in SPARQL searches if you want to give a time line? How does the option agree with the general P49/P50 use on items?
An organisation can run through dozens of name changes over the years - e.g. an Early Modern Publishing house with name changes whenever a father hands down the business to son, wife, son in law etc.
We are presently using Property:P57 for a history of naming but that is not ideal since usual searches will not get to the the right names at the right moment.
We created two properties for this: Property:P233 names the object - a book edition, a manuscript or any other thing that is genetically earlier. Property:P234 comes as the qualifier and offers a statement on what basis the object can be seen as a following. You might for instance link a translation to the edition that gave the original text.
The organisation is top down chronological (the guide lines in the picture above are not that beautiful, but dates on y-axis would be cool).
Objects can have multiple connections to earlier Items (a medieval scribe could use two books to create a new version of the text).
It would be cool if the P234 information became available on the lines that ar connecting items.
One of the problems is here also: How do I select a family of items?
The situation at a particular point in time
Think of a house: Tenants are moving in and out - we can model that with Property:P239 "resident" and P49/50 qualifiers. You are now interested in the situation at a point in history: Who were the tenants on March 3, 1848?
If we can get this done for a house like Item:Q14572 we might be able to show a city at a point in time.