WITH IMPRESSIVE TALENT to assist him, Marion Barry had taken office as mayor of the District of Columbia with the same command presence he demonstrated so well in seeking it. Perhaps it is merely the fresh spirit of a new administration that seems to be generating a sense in the community that improvements are in the offing. But again yesterday, in his second major mayoral address to the community, Mr. Barry vigorously reaffirmed his determination to produce a government of "commitment, competence and compassion." And the 2.600 business, professional and labor representatives who heard him speak were not just being polite in their reaction. With hearty applause, they were eager to share Vice President Mondale's assessment that Washington is "one of the most marvelous cities in the world; it's downright classy -- and we've got a downright classy mayor."

As you might expect, we, too, are pleased to join in the community's warm welcome and its hopes for great strides under the new local administration. There is, as Mayor Barry pointed out forcefully to the assembled leaders, much to be done to improve the efficiency and responsiveness of the government. And he bluntly told business leaders that they should do more to hire people from the city, where unemployment among youths is most severe, and to assist minority-enterprise efforts. In return, Mayor Barry pledged to end the frustration and red tape connected with getting permits from City Hall and to encouage new economic development in all corners of the community.

None of what Mr. Barry is saying is all that extraordinary -- but there is promise in this younger leadership, in the talk of what can be done rather than what cannot. As he did in his campaign, Mayor Barry is speaking in terms of "setting the tone," of delegating authority to competent subordinates, of removing incompetents swiftly -- and of making policy and initiating action.

Obviously the euphoria of the new day in City Hall will give way to some mix of accomplishments and failures. And the Barry record will not be an easy one to judge at the beginning; we know the bureaucracy is bloated and unresponsive, that Congress is often overbearing in its oversight and that some of Washington's problems are -- or have seemed to be -- very nearly intractable. What we can't be sure of is just how much of this is endemic and how much is owing to past mismanagement or indifference -- or incompetence. The new mayor, we would argue, is entitled to a certain amount of public patience -- but not too much, given his own confident pledges of improved performance. For now, Marion Barry deserves the best wishes of us all for a successful administration.