13. Erasure: SI, SA, SU

   si  SI  erase word
    sa  SA  erase phrase
    su  SU  erase discourse

13.1)    ti gerku si mlatu
    This is-a-dog, er, is-a-cat.

13.2)    ta blanu zdani si si xekri zdani
    That is-a-blue house, er, er, is-a-black house.

13.3)    zo .bab. se cmene zo si si si la bab.
    The-word ``Bob'' is-the-name-of the word ``si'', er, er, Bob.

The first use of ``si'' does not erase anything, but completes the ``zo'' quotation. Two more ``si'' cmavo are then necessary to erase the first ``si'' and the ``zo''.

Incorrect names can likewise cause trouble with ``si'':

13.4)    mi tavla fo la .esperanto
        si si .esperanton.
    I talk in-language that-named ``and'' ``speranto'',
        er, er, Esperanto.

The Lojbanized spelling ``.esperanto'' breaks up, as a consequence of the Lojban morphology rules (see Chapter 4) into two Lojban words, the cmavo ``.e'' and the undefined fu'ivla ``speranto''. Therefore, two ``si'' cmavo are needed to erase them. Of course, ``.e speranto'' is not grammatical after ``la'', but recognition of ``si'' is done before grammatical analysis.

Even more messy is the result of an incorrect ``zoi'':

13.5)    mi cusku zoi fy. gy. .fy.
        si si si si zo .djan
    I express [foreign] [quote] ``sy'' [unquote],
        er, er, er, er, ``John''.

In Example 13.5, the first ``fy'' is taken to be the delimiting word. The next word must be different from the delimiting word, and ``gy.'', the Lojban name for the letter ``g'', was chosen arbitrarily. Then the delimiting word must be repeated. For purposes of ``si'' erasure, the entire quoted text is taken to be a word, so four words have been uttered, and four more ``si'' cmavo are needed to erase them altogether. Similarly, a stray ``lo'u'' quotation mark must be erased with ``fy. le'u si si si'', by completing the quotation and then erasing it all with three ``si'' cmavo.

What if less than the entire ``zo'' or ``zoi'' construct is erased? The result is something which has a loose ``zo'' or ``zoi'' in it, without its expected sequels, and which is incurably ungrammatical. Thus, to erase just the word quoted by ``zo'', it turns out to be necessary to erase the ``zo'' as well:

13.6)    mi se cmene zo .djan.
        si si zo .djordj.
    I am-named-by the-word ``John'',
        er, er, the-word ``George''.

The parser will reject ``zo .djan. si .djordj.'', because in that context ``djordj.'' is a name (of selma'o CMENE) rather than a quoted word.

Note: The current machine parser does not implement ``si'' erasure.

As the above examples plainly show, precise erasures with ``si'' can be extremely hard to get right. Therefore, the cmavo ``sa'' (of selma'o SA) is provided for erasing more than one word. The cmavo following ``sa'' should be the starting marker of some grammatical construct. The effect of the ``sa'' is to erase back to and including the last starting marker of the same kind. For example:

13.7)    mi viska le sa .i mi cusku zo .djan.
    I see the  ...  I say the-word ``John''.

Since the word following ``sa'' is ``.i'', the sentence separator, its effect is to erase the preceding sentence. So Example 13.7 is equivalent to:

13.8)    mi cusku zo .djan.

Another example, erasing a partial description rather than a partial sentence:

13.9)    mi viska le blanu zdan. sa le xekri zdani
    I see the blue hou ...  the black house.

In Example 13.9, ``le blanu zdan.'' is ungrammatical, but clearly reflects the speaker's original intention to say ``le blanu zdani''. However, the ``zdani'' was cut off before the end and changed into a name. The entire ungrammatical ``le'' construct is erased and replaced by ``le xekri zdani''.

Note: The current machine parser does not implement ``sa'' erasure. Getting ``sa'' right is even more difficult (for a computer) than getting ``si'' right, as the behavior of ``si'' is defined in terms of words rather than in terms of grammatical constructs (possibly incorrect ones) and words are conceptually simpler entities. On the other hand, ``sa'' is generally easier for human beings, because the rules for using it correctly are less finicky.

The cmavo ``su'' (of selma'o SU) is yet another metalinguistic operator that erases the entire text. However, if the text involves multiple speakers, then ``su'' will only erase the remarks made by the one who said it, unless that speaker has said nothing. Therefore ``susu'' is needed to eradicate a whole discussion in conversation.

Note: The current machine parser does not implement either ``su'' or ``susu'' erasure.