BEIJING has tightened up rules and protocols governing exchanges between mainland scholars and their Taiwanese counterparts. Chinese academics are being asked to exercise caution on titles and designations when referring to Taiwan in order to avoid possible implications of ''two Chinas'' or ''one China, one Taiwan'', an informed source said. He said that meetings had been held recently in most institutes of higher education for cadres in foreign affairs offices, which handle relations with Hong Kong, Taiwan and foreign countries. Those meetings highlighted taboos in academic exchanges. A confidential paper, delivered orally, reiterated that Taiwan should be referred as ''Taipei, China'' or ''Taiwan, China''. ''Chinese Taipei'' should only be used for athletic events, the source said. ''It states very clearly that the punctuation can only be a comma,'' he said. Beijing has always regarded Taipei as a renegade province, insisting that reunification is to take place through peaceful means and on a ''one country, two systems'' model. ''It's always the policy that Taiwan should be addressed as such,'' the source added. ''But they are more cautious and don't want anything to go wrong now that Taiwan President Lee Teng-hui's separatist sentiments have become more apparent.'' The source described the present situation as ''lax externally, tense internally''. In June, Beijing launched a campaign strongly criticising both the Taiwan President's advocacy of independence and his diplomatic policy which, Beijing argued, was aimed at creating ''two Chinas'' or ''one China, one Taiwan''. The source said the foreign affairs officials were told in recent meetings that no invitations should be extended to Taiwan scholars for conferences held on the mainland, except those concerning cross-Strait relations. ''If Taiwan scholars know about these conferences and want to participate, then they will have to apply themselves. ''The decision would be rest with the relevant authorities,'' he said. Foreign affairs officials were also reminded that except those on cross-Strait relations, no mainland scholars should accept invitations to international conferences hosted by Taiwan, the source said. ''These rules have been there all the time. The problem is that they have not been so strictly observed especially in times when relations between the two places are good,'' he said. Meanwhile, Taipei yesterday abruptly called a halt to a visit, scheduled mid-September, of Taiwan media to the mainland. Taiwan's semi-official Strait Exchange Foundation received an order from its superior, the Cabinet-level Mainland Affairs Council, to hold and postpone the scheduled visit until late this year.