Can the same property value be stored only once in the property table

[Error806]

I have a lot of features that have the same string property values, and it seems that the same number of strings as the features need to be written to the table whether stored in b3dm's batchtable or glTF's EXT_structural_metadata extensions. Is it possible to store the same property value only once, and all feature's property refer to this value? Thanks. (From google translate)

[lilleyse]

Currently it's not possible, but I have two ideas for this:

• The glTF could have two property tables, where the first one stores all the unique strings and the second one stores indexes that point to the strings. The actual code for looking up the string would need to be part of the app.
• stringOffsets could be a list of pairs, e.g. [offset, length][offset, length]... instead of [offset][offset]...

[Error806]

Thank you. I will try these ideas

[lilleyse]

Sounds good @Error806

And just to clarify you can try out the first idea now, but the second idea would require a spec change.

[javagl]

There are probably different options here, and maybe some details have to be clarified. Examples could help for the high-level pickture.

If this is about a table like

 ID  |  value
  0  |  "SomeExampleString"
  1  |  "SomeExampleString"
  2  |  "SomeExampleString"
  3  |  "SomeExampleString"
  ...
100  |  "SomeOtherExampleString"
101  |  "SomeOtherExampleString"
102  |  "SomeOtherExampleString"
103  |  "SomeOtherExampleString"
  ...
200  |  "AndYetAnotherString"
201  |  "AndYetAnotherString"
202  |  "AndYetAnotherString"
203  |  "AndYetAnotherString"

then it could indeed be wasteful to store the same string values many, many times. Depending on the exact structure, it should be possible to alleviate that with the first suggestion by Sean, as in

 ID  | stringId
  0  | 0
  1  | 0
  2  | 0
  3  | 0
  ...
100  | 1
101  | 1
102  | 1
103  | 1
  ...
200  | 2
201  | 2
202  | 2
203  | 2

with the stringId being a small (maybe UINT8) type that serves for the redirection into the table that contains the string values:

 ID  |  value
  0  |  "SomeExampleString"
  1  |  "SomeOtherExampleString"
  2  |  "AndYetAnotherString"

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If this does not address the point here, then feel free to reopen this issue.