SharedBook uses a REST-like method syntax. "REST is a style of software architecture for distributed hypermedia systems such as the World Wide Web." See the Wikipedia entry on REST for more details...
The signature is required for all API calls that use an authentication token. Signatures are hash values calculated from the other parameters, using your secret word concatenated with the other arguments as described below:
Request formats look like the following URL (remove any spaces or line breaks, they're just included to make line breaks work on this page):
http://api.sharedbook.com/v0.6/bms/addPhoto? apiKey=[API_KEY]&bmsId=[BMS_ID]&sessionToken= [SESSION_TOKEN]&photo=[PHOTO_PATH]&caption= [USER'S_CAPTION]&ownerName=[NAME]&time=[TIME]&photoId= [PHOTO_ID]&signature=[SIGNATURE]
<bms.comment status="ok"> <comment id=[COMMENT_ID] /> </bms.comment>
<[METHOD_NAME] status="fail"> <error code="[error-code]" msg="[error-message]" /> </[METHOD_NAME]>