WIMBLEDON, England - Who says the oldest and most tradition-laden of tennis' major championships doesn't change with the times?

There is, at long last, a retractable roof atop Centre Court at Wimbledon this year. Video review of line calls and equal prize money for men and women came along ages ago (in 2007 anyway).

But grass is still the court surface, players still wear white, and a day off is scheduled on the middle Sunday of a tournament that was first held in 1877. And something else that stays the same at the All England Lawn Tennis and Croquet Club: Venus Williams and Serena Williams are the women to beat.

Venus, in particular.

She has won five titles, including the last two, at Wimbledon, which begins today. Serena has won this Grand Slam tournament twice, beating Venus in the 2002 and '03 finals, and losing to her in last year's championship match.

While the names and faces at the top of women's tennis keep switching, the Williams sisters have participated in eight of the past nine Wimbledon finals.

"Serena and I, we often talk about that, 'Wonder what happened to them?' We're still here, and we're not leaving," Venus said yesterday, 2 days before she will begin her attempt to become the first woman since Steffi Graf in 1991-93 to win three consecutive Wimbledon championships.

"It's been a real blessing to have the success that we've had and to be able to be still playing great tennis at this point, obviously with the outlook of still playing great tennis for years to come," Venus continued. "I don't see anything changing for a while."

As the defending women's champion, No. 3-seeded Venus is slated to play her first match on Centre Court, against Stefanie Voegele, of Switzerland. Second-seeded Serena starts on Day 1 against 154th-ranked Neuza Silva, of Portugal, on Centre Court, after Roger Federer meets Yen-hsun Lee, of Taiwan, in what could be the first match in the 132-year history of Wimbledon to be played indoors, since there is a 20 percent chance of rain in London.

The new translucent roof on Centre Court, an arena that dates to 1922, takes about 10 minutes to close and should eliminate those days when zero tennis is played because of rain.

"Might be more intimate," said Federer, who lost a five-set thriller of a final last year to Rafael Nadal, a no-show in 2009 because of bad knees. "You're not looking for rain, [but] looking forward to experience it."

Federer begins his bid for a sixth Wimbledon championship, and a record-breaking 15th major title, 2 weeks after completing a career Grand Slam by winning the French Open. Neither Williams fared that well in Paris, Venus losing in the third round and Serena in the quarterfinals. *