54. In a system for interchanging documents between document processing systems, apparatus for translating a first document structure representing a document into a second document structure representing the document comprising: (1) first receiving means for receiving the first structure; (2) extraction means connected to the first receiving means and responsive to the first structure for producing an interchange document structure representing the document and consisting of one or more nestable segments for representing components of the document by, for any component of the first document structure, translating the component into a first segment of the interchange document structure and if the component being translated has a dependent component containing information required in the component being translated, translating the dependent component into a second segment of the sequential document structure which is nested at a point in the first segment corresponding to the point in the component being translated where the information is required; (3) second receiving means connected to the extraction means for receiving the interchange structure; (4) composition means connected to the second receiving means and responsive to the interchange structure for receiving the interchange structure and producing the second structure therefrom by sequentially translating any segment of the interchange structure into a first component of the second document structure until a nested segment is encountered, suspending translation of the segment containing the nested segment, sequentially translating the nested segment into a second component of the nested structure, arranging the second component relative to the first component as required by the second document structure, and resuming translation of the segment; and (5) third receiving means connected to the composition means for receiving the second structure, whereby the first structure is translated into the second structure.
54. In a system for interchanging documents between document processing systems, apparatus for translating a first document structure representing a document into a second document structure representing the document comprising: (1) first receiving means for receiving the first structure; (2) extraction means connected to the first receiving means and responsive to the first structure for producing an interchange document structure representing the document and consisting of one or more nestable segments for representing components of the document by, for any component of the first document structure, translating the component into a first segment of the interchange document structure and if the component being translated has a dependent component containing information required in the component being translated, translating the dependent component into a second segment of the sequential document structure which is nested at a point in the first segment corresponding to the point in the component being translated where the information is required; (3) second receiving means connected to the extraction means for receiving the interchange structure; (4) composition means connected to the second receiving means and responsive to the interchange structure for receiving the interchange structure and producing the second structure therefrom by sequentially translating any segment of the interchange structure into a first component of the second document structure until a nested segment is encountered, suspending translation of the segment containing the nested segment, sequentially translating the nested segment into a second component of the nested structure, arranging the second component relative to the first component as required by the second document structure, and resuming translation of the segment; and (5) third receiving means connected to the composition means for receiving the second structure, whereby the first structure is translated into the second structure. 55. In the apparatus of claim 54 and wherein: the composition means begins producing the second structure before the extraction means is finished producing the interchange structure.