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Re: [sgf-std] New SGF property: transposition / links

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  • Arno Hollosi
    ... I would certainly add such an option to SGFC. ... I tend to agree with Bill. I think that most of us agree that we should keep the SGF game tree a
    Message 1 of 12 , Jul 29, 2008
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      Stuart asked:
      > Is the plan to extend sgfc to cover this and optionally expand trees?

      I would certainly add such an option to SGFC.

      Bill wrote:
      >> TP is fine with me, but the requirement that it's target N[] appear
      >> before the matching TP[] is strange. Why have it?

      I tend to agree with Bill. I think that most of us agree that we should
      keep the SGF game tree a directed, non-cylic graph. However, as Bill
      pointed out, as soon as someone reorders variations the TP[] and subtree
      denoted by N[] would have to change place as well. That is not exactly
      easy on programmers either. Thus I side with no restriction on N[]
      appearing before TP[] in the file.

      I am undecided about keeping TP[] out of the main branch. It makes some
      sense, as SGF's tree order allows programs to ignore variations and
      still read the main line.

      Michal wrote:
      > when I was making my private sgf extension to solve this, I made the
      > Label/Pointer tags but the pointer tag also contained information
      > about transformation (axes, colors), so the dictionary joseki didn't
      > need to repeat any variations with same logic.

      I have not thought about this before, but I have no objections (but, see
      below.)


      The issue I am currently thinking about is the exact semantics of TP[]
      and its implications. If we think of it as a macro that actually
      copies/expands to the subtree denoted by N[] we "mostly" know how to
      display the result.

      But can we really copy all properties as is? E.g. if transformations are
      allowed (axes, colors) what about comments like "in the upper left
      corner" or annotation properties like GB/GW (good for black/white), just
      to name a few issues.

      Also, how does navigation behave and look like? Is it really identical
      to a file that had its TP[]-macros expanded and replaced? Or does the
      standard have to mention some special issues? (Recall the mess about
      displaying variations as siblings or children.)

      Important issue: what about editing/writing such a file? Suppose I don't
      want to write the expanded tree, but the compressed macro-version. How
      does the user control whether changing a node affects both subtrees
      (N[]'s and TP[]'s) or only one of them (if the display looks exactly the
      same)? How do I tell the SGF program to create a new TP[] or
      remove/split/copy the tree denoted by N[]. I think the GUI issues (and
      therefore the usability of this extension) are not to be underestimated.


      Your opinions?


      Apart from TP[] I really think we should have something like a real
      link, where the semantics mean jumping to another node, not copying its
      subtree. The semantics for links, the navigation, display, etc. are much
      easier for links than for macro-like TP[].

      /Arno
    • Stuart A. Yeates
      ... I m also interested in the exact semantics of TP[] with respect to ko calculations. If two subtrees have different previous board positions (as opposed to
      Message 2 of 12 , Jul 29, 2008
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        On Wed, Jul 30, 2008 at 9:46 AM, Arno Hollosi <ahollosi@...> wrote:

        > The issue I am currently thinking about is the exact semantics of TP[] and
        > its implications. If we think of it as a macro that actually copies/expands
        > to the subtree denoted by N[] we "mostly" know how to display the result.

        I'm also interested in the exact semantics of TP[] with respect to ko
        calculations. If two subtrees have different previous board positions
        (as opposed to the same previous board positions in a different order)
        their children may have different legal moves. This is mainly an issue
        when considering the endgame rather then the opening book, of course.

        > Important issue: what about editing/writing such a file? Suppose I don't
        > want to write the expanded tree, but the compressed macro-version. How does
        > the user control whether changing a node affects both subtrees (N[]'s and
        > TP[]'s) or only one of them (if the display looks exactly the same)? How do
        > I tell the SGF program to create a new TP[] or remove/split/copy the tree
        > denoted by N[]. I think the GUI issues (and therefore the usability of this
        > extension) are not to be underestimated.

        The SGF file format has succeeded by being a file format. Specifying
        the way a program interacts with a user should be left up the program
        author. I hope/imagine that most programs will make the presence or
        absence of N[]'s and TP[]'s invisible to the user.

        cheers
        stuart
      • Arno Hollosi
        ... Sometimes the GUI or interaction with the user has to be addressed in the specification. That s the reason why we have a ST[] property. I am just trying to
        Message 3 of 12 , Jul 30, 2008
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          > The SGF file format has succeeded by being a file format. Specifying
          > the way a program interacts with a user should be left up the program
          > author.

          Sometimes the GUI or interaction with the user has to be addressed in
          the specification. That's the reason why we have a ST[] property. I am
          just trying to find out if someone thinks there may be issues.

          > I hope/imagine that most programs will make the presence or
          > absence of N[]'s and TP[]'s invisible to the user.

          I think that depends. When I am editing I'd like to know whether my
          change is copied multiple times within the SGF tree or is a local
          modification only. Furthermore, when I know that the subtree is copied
          (and maybe transformed) I know that I should avoid comments like "upper
          right corner" or "B5 should be at C17".

          /Arno
        • Lauri Paatero
          Hi, I think idea is good, but there are several problems with initial proposal that need some resolution: 1. N property Property N is inteded to be
          Message 4 of 12 , Jul 30, 2008
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            Hi,

            I think idea is good, but there are several problems with initial
            proposal that need some resolution:

            1. N property

            Property N is inteded to be user-visible and editable name for node. So
            duplicated exists, and preventing user from giving same node name twice
            in file is bad solution.

            I think it would be better to define some other property (for example
            AC[ int ]), that could be used to reference node in all cases it is
            machine referenced. (I have planned such id for other uses, but I would
            prefer having single standard one.)

            Proposal: define new invisible-to-user property AC[nro] for node, and
            use that to reference to node.

            2. Loops

            I would like to say loops are not allowed, bu:

            If we consider following chain of editing
            1. create file which contain new properties;
            2. edit file with editor that does not know new properties (they
            continue to exists a long time).
            3. Open file again with editor understanding new properties.

            Now at step 3 we may have loops, as at step 2 there is no way new rules
            are followed, even though editor was SGF4-compliant.
            So I think we should not add new restrictions to what is valid file.
            Loops will exists, and programs need to be able to deal with them.
            Also nodes with TP might not be leaf nodes anymore.

            So in essence new limitations would invalidate SGF4-compliance of
            program, which is exactly what standards are supposed to prevent.

            Proposal: No new restrictions to SGF4 file structure.

            3. Link interpretation

            I think we should have 2 types of links:
            - Just jump to location, as user would have moved to location (so TP
            does not need to be leaf)
            - Continue with referenced subtree, as proposed here.

            t.
            Lauri Paatero


            Arno Hollosi wrote:
            >> The SGF file format has succeeded by being a file format. Specifying
            >> the way a program interacts with a user should be left up the program
            >> author.
            >>
            >
            > Sometimes the GUI or interaction with the user has to be addressed in
            > the specification. That's the reason why we have a ST[] property. I am
            > just trying to find out if someone thinks there may be issues.
            >
            >
            >> I hope/imagine that most programs will make the presence or
            >> absence of N[]'s and TP[]'s invisible to the user.
            >>
            >
            > I think that depends. When I am editing I'd like to know whether my
            > change is copied multiple times within the SGF tree or is a local
            > modification only. Furthermore, when I know that the subtree is copied
            > (and maybe transformed) I know that I should avoid comments like "upper
            > right corner" or "B5 should be at C17".
            >
            > /Arno
            >
            > ------------------------------------
            >
            > SGF spec: http://www.red-bean.com/sgf/
            > Contact: Arno Hollosi <ahollosi@...>Yahoo! Groups Links
            >
            >
            >
            >
            >
          • David Bush
            ... Not only that, but if the target node is pointed to by more than one TP, you would have to make sure N comes before all of them. ... I guess it depends on
            Message 5 of 12 , Jul 30, 2008
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              > Bill wrote:
              > TP is fine with me, but the requirement that it's target N[] appear
              > before the matching TP[] is strange. Why have it?
              >
              > I tend to agree with Bill. I think that most of us agree that we
              > should keep the SGF game tree a directed, non-cylic graph. However,
              > as Bill pointed out, as soon as someone reorders variations the
              > TP[] and subtree denoted by N[] would have to change place as well.

              Not only that, but if the target node is pointed to by more than one
              TP, you would have to make sure N comes before all of them.

              > That is not exactly easy on programmers either.

              I guess it depends on what the program does. It wouldn't necessarily
              be a problem if the program deals with an expanded tree instead of the
              compressed file.

              The purpose of TP is to make generation of a file manually with a text
              editor a little less tedious. If you have software that can save a
              file in SGF format from a game tree generated with a GUI, ***THERE
              SHOULD BE NO NEED TO DEAL WITH TP.*** So as far as I can tell, the
              problem of reordering a file is based on the assumption that this
              reordering is done manually, with a text editor. Just out of
              curiosity, what would be gained by doing this?

              As was pointed out in another post, GUI issues and file loading and
              saving issues should be regarded as independent of each other.

              > Michal wrote:
              > when I was making my private sgf extension to solve this, I made
              > the Label/Pointer tags but the pointer tag also contained
              > information about transformation (axes, colors), so the dictionary
              > joseki didn't need to repeat any variations with same logic.

              Sorry, I missed your point in my earlier post. But I'm not sure what
              scope you want this extra information to apply to. Does a joseki
              dictionary file concern itself entirely with one corner of a 19x19
              board? Or are you talking about referring to another corner of the
              board which was explored earlier in the same file? If the full-board
              positions are not effectively identical by axis/color transformation,
              there could be a problem when software tries to evaluate this
              position. Joseki battles are of course not independent of each other.

              Also, do you generate this dictionary with a GUI or with a text editor?

              > ... If we think of it as a macro that actually
              > copies/expands to the subtree denoted by N[] we "mostly" know how
              > to display the result.
              >
              > But can we really copy all properties as is? E.g. if
              > transformations are allowed (axes, colors) what about comments like
              > "in the upper left corner" or annotation properties like GB/GW
              > (good for black/white), just to name a few issues.

              Whether TP is a macro call or a link, these same issues would crop up.
              GB versus GW could be automatically taken care of. You could just
              ignore all comments in an copied subtree, or not copy them in the
              first place if there is any kind of axis/color change.

              > Important issue: what about editing/writing such a file? Suppose I
              > don't want to write the expanded tree, but the compressed macro-
              > version. How does the user control whether changing a node affects
              > both subtrees (N[]'s and TP[]'s) or only one of them (if the
              > display looks exactly the same)?

              Under what circumstances would you want to change one subtree but not
              the other? I'm not asking about axis/color changes here. Why should
              the user have this option to make the subtrees of the compressed file
              different?

              > How do I tell the SGF program to create a new TP[] or
              > remove/split/copy the tree denoted by N[]. I think the GUI issues
              > (and therefore the usability of this extension) are not to be
              > underestimated.

              Is this SGF program a text editor or a GUI? If it's a GUI which can
              save files in SGF format, why would you want to deal with TP calls?

              > The semantics for links, the navigation, display, etc. are much
              > easier for links than for macro-like TP[].

              I don't mean to require programmers to treat TP one way or the other.
              The SGF definition should work for any way the programmer wants to use
              it. I just used the "macro" analogy as a way of explaining what I was
              talking about. Sorry if I wasn't clear about that.

              syeates said:
              > I'm also interested in the exact semantics of TP[] with respect to
              > ko calculations. If two subtrees have different previous board
              > positions (as opposed to the same previous board positions in a
              > different order) their children may have different legal moves.
              > This is mainly an issue when considering the endgame rather then
              > the opening book, of course.

              My proposal is that the positions need not be identical as long as
              every move, position evaluation, and everything else that gets copied
              or linked to is equally valid in both situations. If there are
              "irreconcilable differences" then they should be different subtrees.
              In a ko situation, and perhaps for the most part in Go, different
              battles are arguably not truly independent of each other, because one
              usually is more important than the others at any given point. So TP
              calls might not be appropriate if the subtree in question is large.

              Also I recommend you take a look at my LO[] proposal (in a separate
              thread) for dealing with LOcal battles.
            • Mark Lentczner
              The big issue I see to resolve is the semantic of the link. I see several possibilities discussed in the thread, and I m going to try to restate the
              Message 6 of 12 , Jul 30, 2008
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                The big issue I see to resolve is the semantic of the link. I see
                several possibilities discussed in the thread, and I'm going to try to
                restate the concisely:

                1) Identity
                The node referenced is the identical position as the node with the
                link. Presumably they have the same position *after* each has applied
                any moves.

                2) Duplicate Sub-tree
                The nodes that follow the referenced node are equally applicable to
                the position at this node.

                3) Jump
                The referenced node should be offered to the user as a possible follow
                on to this node. The position at the referenced node could be wholly
                different.

                Identity seems to have a number difficulties in definition and
                resiliency:
                - just how "identical" do the positions have to be?
                - i.e.: same number of prisoners? or just same delta? passes?
                - same comments? markup?
                - what about differing in only a tenuki move?

                Duplicate Sub-tree has the downside that now each node can no longer
                be transformed into a single game position, since the state of the
                game will depend on if you took a jump to get there.

                Jump gets around these difficulties, but at the expense of being a
                different kind of navigation that the existing options.

                One way to approach the choice is to look at the use cases and see
                which admits the most flexibility. The use cases I see are:

                A) Joseki dictionary desire to not replicate whole sub-trees when a
                position can be arrived at via two different move sequences. This use
                case could be broadened to include color and spacial transposition, or
                differing in tenuki.

                B) Tsumego. Like joseki, a desire to not replicate whole sub-trees.
                Here the game state identity requirement might be more rigorous.
                GoProblems.com already does this automatically by identifying
                identical positions in the tree: If one has follow on nodes and the
                other doesn't -- they are "spliced".

                C) General annotation need to have variant lines or main lines
                reference other lines within the tree.

                It seems to me that the Jump semantic supports all of these. If there
                is a need for identical position at both ends, it is easy enough for
                the creation tool to enforce that.

                The only thing that then needs to be addressed is the intended user
                navigation: Is it displayed as an option? Is it followed
                automatically? One could support both by this rule: If the LI[]/TP[]
                property appears as the only property in a node, then the link should
                be immediately followed, replacing the game state with the state at
                the target node. On the other hand, if there are any other
                properties, including just a comment (even an empty comment!), then
                the user is offered link as a sort of 'remote variation', and can
                choose, as they would choose a variant, to continue in that part of
                the tree.

                - Mark
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