ROME – Formally speaking, Vatican documents are categorized according to their ecclesiastical genre. An “encyclical”, for instance, is a developed form of papal teaching, an “instruction” generally explains or amplifies another document that has legislative force, a “motu proprio” is a legal decree under the pope’s authority, and so on.

Informally, however, one could envision more amusing taxonomies for the texts churned out by various Vatican departments and figures: “Useful” versus “irrelevant,” for instance, or “readable” versus “hopelessly obtuse.”

On that landscape, here’s another category I’ve long felt would be useful: Documents that cause a huge fuss in the media, but change little on the ground.

As a classic for-instance, take Pope Benedict XVI’s 2007 decree liberalizing permission for celebration of the older Latin Mass. It sparked widespread debate, with many liberals seeing it as an attempt to roll back the clock on the reforms of the Second Vatican Council (1962-65), and traditionalists predicting it would transform Catholic worship in the direction of sobriety and reverence.

Almost a decade later, however, its practical effect has been fairly limited. Most Catholics who wanted access to the older Mass already had it, and neither the apocalypse nor the renaissance suggested by overheated commentary ever occurred.

I suspect we may be on the brink of another of these “symbolically huge but practically small” documents in early April.

The Vatican announced Thursday that Pope Francis’s highly anticipated apostolic exhortation on the family will be released April 8, and that it will be presented in a news conference by Cardinal Cristoph Schönborn of Vienna, Austria.

Schönborn sided with the progressives during the two Synods of Bishops on the family on the hot-button issue of allowing some divorced and civilly remarried believers to return to Communion, and by selecting him to present the text, the Vatican may have tipped its hand about what it contains.

Assuming so, it likely will be touted in the blogosphere and in the press as a sort of Catholic Waterloo. Liberals will hail the pope for loosening up, while conservatives will fret about a surrender on teaching and tradition.

In effect, it may be Humanae Vitae, Pope Paul VI’s 1968 encyclical on birth control, in reverse – instead of protest on one side of the street because a pope said “no,” we may see an uprising on the other side because a different pope, on a different topic and in a different time, said “yes.”

Here’s why, however, it may not mean a great deal in the trenches.

First, there certainly are lots of divorced and remarried Catholics out there, so in theory the pool of people who could be affected by a change in discipline on reception of Communion is fairly vast. In the United States alone, the estimate is that there are 4.5 million such folks.

The reality, however, is that many of those Catholics aren’t going to Mass, just like all kinds of other Catholics who, for one reason or another, have drifted away, and it’s not clear the possibility of receiving Communion after some sort of discernment or “penitential path” would be enough to lure them back.

Second, many of those who are going to Mass today are already receiving Communion.

At the parish level, everyone knows there are plenty of pastors who have quietly told these people it’s okay to come up in the Communion line and receive the sacrament. If they haven’t said it out loud, they’ve made the statement simply by giving them Communion every time they present themselves.

Catholics engage in what’s colloquially known as “parish shopping” all the time for a variety of reasons – whose music you like better, which priest is the better homilist, where the cry room has toys your kids like, and so on. If you’re divorced and remarried, finding a pastor who’s not going to make an issue out of Communion is often just another item on the list.

Bear in mind, Pope Francis is unlikely simply to say, “From now on, Communion is wide open to everybody.” Instead, the idea probably will be that each situation be handled on a case-by-case basis through something called the “internal forum,” meaning private exchanges between believers and their confessors.

In reality, however, that’s pretty much already the situation. Maybe some divorced and remarried Catholics will feel better that a pope has said it out loud, but it probably won’t have much practical impact on what they actually experience.

We shouldn’t minimize the pain, of course, of that small number of divorced and civilly remarried Catholics who do still go to Mass, and who don’t come forward for Communion because they want to be faithful to Church teaching on marriage.

Yet many of those folks may not avail themselves of whatever new door Francis perhaps will open, precisely because they believe the current rules are valid and they’ve made their peace with the situation.

Some of these people actually have been on the front lines of the debates over the two synods, arguing for upholding tradition, and it likely would strike them as hypocritical to turn around now and take advantage of an innovation they opposed on principle.

All this, of course, won’t stop the firestorm of commentary and debate the pope’s document is certain to trigger, and undeniably there are theological and sacramental concerns of towering importance at the heart of whatever choice Francis is about to make.

Looking around, however, does suggest a dose of caution if anyone is expecting his decision to change the world.