Improved address object design

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When we decided to chain together address objects with a parentIndex property, we failed to understand that offset should be relative to parent rather than to base address.

1. Specify that offset is w.r.t. parent.

2. Rename offset to offsetFromParent to avoid natural baseAddress + offset error.

3. Specify address resolution algorithm.

4. CONSIDER other kinds such as "headers" (start of header list), "sections" (start of section list), "header", "tables", "table".

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REVISED PROPOSAL

• Rename baseAddress to effectiveAddress. It is the result of adding up all the parent offsets (assuming all the ancestors have offsets). Its presence allows some ancestors not to specify offsets.
• Rename offset to offsetFromParent. Even though there is no longer a baseAddress property, it's still good to be explicit about this.
• Specify address resolution algorithm.
• Add two kind values:
  • "header": A data structure at the beginning of an addressable region that specifies the layout and location of objects in the remainder of the region.
  • "table": A contiguous region of addressable space with a distinct purpose and a specified internal organization

[ghost]

Harlene is making these changes in the SDK and I will review. Removing the schema-todo label.