The doctrine of the Assumption says that at the end of her life on earth Mary was assumed, body and soul, into heaven, just as Enoch, Elijah, and perhaps others had been before her. It’s also necessary to keep in mind what the Assumption is not. Some people think Catholics believe Mary "ascended" into heaven. That’s not correct. Christ, by his own power, ascended into heaven. Mary was assumed or taken up into heaven by God. She didn’t do it under her own power.
The Church has never formally defined whether she died or not, and the integrity of the doctrine of the Assumption would not be impaired if she did not in fact die, but the almost universal consensus is that she did die. Pope Pius XII, in Munificentissimus Deus (1950), defined that Mary, "after the completion of her earthly life" (note the silence regarding her death), "was assumed body and soul into the glory of heaven."
The possibility of a bodily assumption before the Second Coming is suggested by Matthew 27:52–53: "[T]he tombs also were opened, and many bodies of the saints who had fallen asleep were raised, and coming out of the tombs after his resurrection they went into the holy city and appeared to many." Did all these Old Testament saints die and have to be buried all over again? There is no record of that, but it is recorded by early Church writers that they were assumed into heaven, or at least into that temporary state of rest and happiness often called "paradise," where the righteous people from the Old Testament era waited until Christ’s resurrection (cf. Luke 16:22, 23:43; Heb. 11:1–40; 1 Pet. 4:6), after which they were brought into the eternal bliss of heaven.
There is also what might be called the negative historical proof for Mary’s Assumption. It is easy to document that, from the first, Christians gave homage to saints, including many about whom we now know little or nothing. Cities vied for the title of the last resting place of the most famous saints. Rome, for example, houses the tombs of Peter and Paul, Peter’s tomb being under the high altar of St. Peter’s Basilica in Rome. In the early Christian centuries relics of saints were zealously guarded and highly prized. The bones of those martyred in the Coliseum, for instance, were quickly gathered up and preserved—there are many accounts of this in the biographies of those who gave their lives for the faith.
It is agreed upon that Mary ended her life in Jerusalem, or perhaps in Ephesus. However, neither those cities nor any other claimed her remains, though there are claims about possessing her (temporary) tomb. And why did no city claim the bones of Mary? Apparently because there weren’t any bones to claim, and people knew it. Here was Mary, certainly the most privileged of all the saints, certainly the most saintly, but we have no record of her bodily remains being venerated anywhere.
Most privileged, I'll buy. Most saintly? It sounds like her son said it was John the Baptist:
"I tell you, among those born of women none is greater than John. Yet the one who is least in the kingdom of God is greater than he.” (Luke 7:28)
You build your faith on perhaps?
>>Some people think Catholics believe Mary "ascended" into heaven.<<
Yeah, change the subject. No one ever said assumption unless they were using the wrong word. Either way it’s a myth.
>>The Church has never formally defined whether she died or not<<
That’s not what the question is. Stop trying to deflect.
>>people from the Old Testament era waited until Christ’s resurrection<<
Mary wasn’t part of the group. She was still alive when Christ arose so would be included in the New Testament saints.
>>There is also what might be called the negative historical proof for Mary’s Assumption.<<
Catholics do like their myths built on “it doesn’t say it didn’t happen” don’t they.
>>It is agreed upon that Mary ended her life in Jerusalem, or perhaps in Ephesus.<<
Prove it. perhaps? Again you’re building you faith and eternal future on perhaps?
>>but we have no record of her bodily remains being venerated anywhere.<<
Take a hint. She wasn’t supposed to be venerated or the apostles would have written about it. As I said earlier, the entire myth of Mariology is just that. Myth. Not sanctioned by scripture.