It seems to me that we are not robots that repeat all data. We are people, they are people, we are all people. And we all perceive reality differently. When asked a question you first interpret the question to determine what, in your mind, is being asked. Then you formulate an answer according to the interpretation. Thus, in formulating the answer we select from the available information that which, to us, is most relevant. Of course, whether we include everything or not is dependent on whether the question asked is formulated in a way that clearly identifies exactly what information is desired. There are lots of places where omission can creep in. There is nothing stopping the other person from asking more questions and starting the response cycle again.

It seems to me a lie includes an intent to deceive. Thus omission, unless intentional, cannot be a lie. Omission is often a matter of a failure to clearly ask or a failure in the interpretation of what was asked. Omission should not be considered as intentional until there is evidence that the omission is intentional in which case the omission can be CONSIDERED a lie even though it still might not be. That is what conversations are for - to further clarify and discuss aspects in a friendly manner so each party understands the other without accusations and attacks on credibility. Assumptions of intent are still just assumptions until the intent is proven.

There is no law that says you must reveal all if you reveal anything. Value judgements, sensitivity to what is hurtful even if true, and different interpretations of what is or is not relevant to the question can easily lead to what is viewed as omission when, in fact, that which was omitted was not considered important to the responder. Communication is a bumpy road. Answer to the best of your ability, followup with a question put to the questioner inquiring whether they have any other questions or concerns. And most of all answer all questions with at lest a friendly tone, i.e. don't get paranoid about questions. It is how we learn new things.