An invitation, in Petaluma, is referred to a message requesting the recipient to attend a particular occasion. Generally this is conveyed in formal, passive language in the form or a letter, either through an e-mail or by post. An invitation is sent in advance to the occasion date to the recipient. An announcement, in Petaluma, denotes the act of publicizing a fact or news. This is done in the form of a broadcast message, a program note or a commercial. However another form of announcement could be an engraved or printed formal statement or notice, as of a wedding or relocation. While announcement is definitely a public phenomenon, invitation may or may not be done publicly.