The definition of the GIF stream and image metadata formats should be modified
to make it impossible to create certain types of inconsistencies.

Stream metadata:

Add a "Version" node to store the file version

"LogicalScreenDescriptor" node:

  Redefine the "colorResolution" attribute to range from 1 to 8 instead of
  from 0 to 7

  Remove the "globalColorTableFlag" attribute as it is redundant with the
  presence or absence of a "GlobalColorTable" node

  Move the "sizeOfGlobalColorTable", "backgroundColorIndex", and "sortFlag"
  attributes to the "GlobalColorTable" node since they are meaningful only
  if such a node is present.

"GlobalColorTable" node:

  Redefine the "sizeOfGlobalColorTable" attribute to hold the actual
  number of table entries instead of the internal representation
  (log_2(#entries) - 1). Enumerate the legal values explicitly in the
  format description.
  
Image metadata:

"ImageDescriptor" node:

  Remove the "localColorTableFlag" attribute as it is redundant with the
  presence or absence of a "LocalColorTable" node

  Move the "sizeOfLocalColorTable" and "sortFlag" attributes to the
  "LocalColorTable" node since they are meaningful only if such a node is
  present.

"LocalColorTable" node:

  Redefine the "sizeOfLocalColorTable" attribute to hold the actual
  number of table entries instead of the internal representation
  (log_2(#entries) - 1). Enumerate the legal values explicitly in the
  format description.

"PlainTextExtension" node:

  Change name of "textGridRight" attribute to "textGridTop", as prior name
  was inaccurate.