Harvard today released a report that sketches key housing, transportation, and landscaping proposals for the University’s long-term expansion into Allston.

The report shows, with graphics for the first time, several of the possibilities for development across the Charles River in Allston that University planners have been discussing publicly for more than a year.

Executives at Cooper, Robertson & Partners, the planning firm that prepared the report, were quick to emphasize that the proposals remained at a conceptual level and that individual buildings had not been designed.

“There’s a series of issues that are academic and not for us to judge upon,” said David McGregor, the firm’s managing director, referring to ongoing dialogue within the University over what schools and departments will move across the river.

Over the summer and fall, Harvard officials will shop the report around to professors, students, and Allston residents for comment. Later, the University must work with the Boston Redevelopment Authority to update its master plan for Allston.

Harvard last changed that plan in 1998, a year after announcing that the school had secretly purchased 52 acres of Allston land through a front company.

Today’s report does not include a timetable for planning or construction. But it does divide Harvard’s Allston holdings into two zones, one available for building by 2010, and another­—which is currently composed mainly of rail yards—that will be constrained for more than five years.

Kathy Spiegelman, Harvard’s top Allston planner, said that the land available in five years includes some tenants whose leases will expire before 2010.

“By no means is this the project of a single decade, or, I suspect, a single generation,” said University President Lawrence H. Summers, speaking in a conference call with reporters today.

But the preliminary designs reinforce several widely-circulated proposals for the development of Allston. Undergraduate Houses, graduate schools and housing, laboratories, and an enhanced Charles River crossing are all components of the report.

A SPACE FOR SCIENCE

One of the administration’s top priorities appears to be the construction of laboratory space to house cutting-edge initiatives like the Harvard Stem Cell Institute.

In April, the Allston Science and Technology Task Force recommended that Harvard build two 500,000-square-foot science facilities.

“The University’s goal is to move forward expeditiously with plans for [the] first building,” today’s report reads. And Summers said he “would not be surprised” to see laboratory construction towards the beginning of Allston development.