My objective for writing the article was the following:
1) Give a brief introduction to SOA assuming that the audience is medium-level developer to application architects/project managers.
2) Provide an overview of the evolution of SOA.
3) Define and provide some explanation of the key components of SOA.
Having said that, with the limitations on the length of the article and the assumption of who would be reading the article, I was not able to provide justification for things such as why we need distributed software, EDI, etc. To do that, I would have had to write several books before I could sufficiently cover all that led to SOA.