Top transport officials gather here today to discuss the future of ports and the maritime industry at the Massachusetts Port Authority's Fifth Annual Maritime Conference.

The meeting entitled "Building Ports, Ships, Rail & Roads: Investment in the 21st Century" will focus on the role of ports and transportation planning in the midst of sweeping worldwide changes affecting the economy and the shipping industry. Some 300 participants are expected to attend.Two major themes will be central to the conference, said Anne D. Aylward, Massport maritime director. The first is the idea of ports as economic infrastructure and the question of the financial underpinnings needed to keep them vital.

"The public has already become aware that somebody needs to figure out in this country how we're going to pay for infrastructure," Ms. Aylward said. ''That's a problem in ports as well."

Ports have been "less than compensatory" in a shipping industry that has also struggled with profitability, but sources of future port funding have yet to be identified, said Ms. Aylward.

The question of how to manage and plan port capacity in the face of shifting economic forces and transportation needs also will be a central theme.

Ms. Aylward cited a host of factors that complicate port planning including political and economic changes affecting trade, labor uncertainties, pooling agreements among carriers and developing rail involvement in intermodal transport.

Panel discussions at the conference will cover topics including economic forces influencing the maritime industry, carrier pricing and profitability, and trends in the shipping industry.

Guest speakers include Christopher J. Rankin, chief executive officer of

Trans Freight Lines; John J. Farrell, president of International Terminal Operating Co.; William F. Rooney, vice president, marketing, Atlantic Division, Sea-Land Service Inc.; and William L. Ralph, vice president, The Journal of Commerce, PIERS service.

Also participating are Harold Holden, executive director, USA-Europe Rate Agreement; Carmen Lunetta, port director, Port of Miami; Richard E. DeGennaro, director intermodal marketing and sales, Consolidated Rail Corp.; Leo J. Donovan, vice president, Booz, Allen & Hamilton Inc.; Michael L. Sclar, vice president, world trade services, Temple, Barker & Sloane Inc.; and Wayne M. Ayers, chief economist, Bank of Boston.