D.C. Mayor Muriel E. Bowser said D.C. agencies will have to justify withholding data from the public. (Katherine Frey/The Washington Post)

D.C. Mayor Muriel E. Bowser pledged to make the nation’s capital a model for government transparency on Tuesday, publishing a far-reaching new open-data policy and appointing a new chief technology officer to help oversee a transformation in how the city shares data with the public.

Access to data has for decades been a source of tension between the city and journalists, contractors and good government advocates, and efforts by past mayoral administrations to encourage more openness have been met with limited success. Some agencies have claimed that years-old computer systems have made publishing raw data on everything from crimes to parking tickets to environmental measurements impossible, while others have been slow to respond to direct requests to release the information.

Bowser said her plan could institutionalize open government by creating a new position of chief data officer, a kind of data ombudsman, and making employees in each agency responsible for figuring out how to share the data. The mayor is launching her plan early enough in her term that longtime skeptics said they were hopeful that real change could be seen in coming years.

“The District’s data shall be open by default,” reads a draft of the proposal that Bowser’s team published online Tuesday. “Agencies must justify why data should not be released publicly in its most complete form rather than the public being obligated to justify why data should be released.”

Bowser’s broad proposal could help her politically by turning a page with good government groups that criticized her attempts last year to restrict access to video from police body-worn cameras. The mayor proposed exempting all footage from review under District public records laws. Objections from the council forced her to accept major changes to that plan, making most video subject to citizen review.

[D.C. could release more body-worn camera footage than other major cities]

The mayor’s open-data plan is also rooted in an attempt to continue branding D.C. as a tech-friendly city and one that embraces innovation and collaboration with the city’s growing number of information technology start-ups.

Bowser said Tuesday that she is re-launching the D.C. Open Government Advisory Board begun under former mayor Vincent C. Gray to get direct feedback from industry leaders and even civil rights leaders about how to better use and publish critical data.

Last week, Bowser’s deputy mayor for planning and economic development launched an open-data dashboard on city economic issues.

After recent criticism from the council about access to crime data, the mayor’s office also said that running tallies of all types of crimes in the city will be updated and released on the police department’s website daily.

Bowser also announced that Archana Vemulapalli will be the District’s new chief technology officer. Vemulapalli held the same position at Pristine Environments, a McLean-based company that manages technology and other facility issues for corporate real estate clients.

The mayor’s first CTO, Tegene Baharu, resigned in October, suggesting in a letter to employees the job had been more political than he had expected.

Matt Bailey, Bowser’s director of technology innovation, encouraged city residents to comment on the draft proposal before Feb. 15.

“We want to think about how to not just make open data big in the District, but how to make it make real change for everybody,” he said.