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Re: [ddlm-group] Data-name character restrictions - one last time
- To: Group finalising DDLm and associated dictionaries <ddlm-group@iucr.org>
- Subject: Re: [ddlm-group] Data-name character restrictions - one last time
- From: David Brown <idbrown@mcmaster.ca>
- Date: Fri, 11 Dec 2009 09:57:33 -0500
- In-Reply-To: <C7485B9C.128AD%nick@csse.uwa.edu.au>
- References: <C7485B9C.128AD%nick@csse.uwa.edu.au>
Data names of the form _xxx[i] only appear in DDL2. In DDL1 tne
corrsponding items are call _atom_site_aniso_U_11 etc. In these cases
it will still be necessary to have explict dictionary entries but
presumably they can be aliased to _atom_site.aniso[1][1] which dREL
etc. would recognize. Davod Nick Spadaccini wrote: I don't think a mechanism for specifying a starting index will work at the individual definition level. They will all have to start at the same address otherwise if I try to access within dREL some other object, how do I know what its starting index is? Best to decide on a starting index and fix it. There is an historical precedent in CIF that has it staring at 1. As wrong as I would argue that is, it is in stone so stick with it. In my code I will simply offset the index by -1 to get to the real storage point (I don't program in languages that index starting at 1) - it I easy enough to do. Seems a solution to me. The _xxx_yyy[] syntax is an ancient category like definition that never appears in data. On 11/12/09 7:37 PM, "Herbert J. Bernstein" <yaya@bernstein-plus-sons.com> wrote:I am saying that any declaration of an array or of a list would make its individual elements available for use in any data CIF without the need for any further declarations in the dictionary. This is simple and clear and completely consistent with dREL. The only really new thing would be some mechanism(s) to specify the starting index. I think this covers John's need. The only thing it would not cover is something like _xxx_yyy[] which appears in some CIF1 dictionaries but not in the data files, so I don't think there should be an issue with not allowing those in CIF2. Does anyone see a problem with this? ===================================================== Herbert J. Bernstein, Professor of Computer Science Dowling College, Kramer Science Center, KSC 121 Idle Hour Blvd, Oakdale, NY, 11769 +1-631-244-3035 yaya@dowling.edu ===================================================== On Fri, 11 Dec 2009, Nick Spadaccini wrote:I can agree with that, if you are saying only the matrix object is available to the user. OR alternatively are you saying there will ONLY be one object defined in the dictionary, let's say the 3x3 matrix _atom_site.U But NEVER have definitions in the dictionary for the individual _atom_site.U[i][j] elements. As we parse a CIF data file, if we detect _atom_site.U[i][j], it isn't in the defined dictionary so this would normally raise an error. BUT because of the specific trailing syntax [i][j] this informs the parser there must be an object of matching rank with the name _atom_site.U (ie the _atom_site.U[i][j] with the [i][j] truncated) in the dictionary - and therefore populate the appropriate element of _atom_site.U with that value. This would circumvent the problem of two different identifiers called _atom_site.U[i][j] in the dictionary BUT would necessarily mean that [i][j] syntax in a data name was reserved for objects that are defined in the dictionary as, in this case, a 2D matrix. They can't (shouldn't?) be used for general data names. Does this cover what John wanted also? On 11/12/09 10:12 AM, "Herbert J. Bernstein" <yaya@bernstein-plus-sons.com> wrote:Actually, the suggestion comes from reading the dREL documentation and the DDLm documentation and noticing how clumsy the access to array elements in DDLm is compared to the access in dREL. What I am suggesting is to promote the dREL access making it fully available at the DDLm level, replacing the clumsy element-by-element definitions with one automatic definition that looks and works just the way one might expect. Regards, Herbert ===================================================== Herbert J. Bernstein, Professor of Computer Science Dowling College, Kramer Science Center, KSC 121 Idle Hour Blvd, Oakdale, NY, 11769 +1-631-244-3035 yaya@dowling.edu ===================================================== On Fri, 11 Dec 2009, Nick Spadaccini wrote:Many of you need to read the dREL part of the dictionary much more closely. dREL extensively exploits access to matrix and vector types by index addressing at a programmatic level. That's how it gets done the things it is has to. So within the dREL programming language you will see littered everywhere a matrix which is accessed via standard indexing (as you would with any language supporting array structures). So lets have a matrix _atom_site.U - within dREL I have access to _atom_site.U[0][0] etc as part of the language (I'll stick with 0 initial indexing but this really is a trivial problem, solved many times over). But now you ALSO want a scalar data item called _atom_site.U[0][0] with in CIF. The dictionary says _atom_site.U[0][0] is a single scalar value. The dREL constructor method for _atom_site.U has _atom_site.U = Matrix([[atom_site.U[0][0] ...]...]) This obviously won't work. This is why the dictionary in DDLm uses the equivalent of _atom_site.U_0_0 for the scalar value so that the above constructor will make sense and still allows me to access _atom_site.U[0][0] from within dREL. It is why I am keen to restrict the syntax of the data names. On 11/12/09 2:46 AM, "Herbert J. Bernstein" <yaya@bernstein-plus-sons.com> wrote:Dear Colleagues, One very neat resolution to this problem would be to allow a list or array-typed CIF2 tag to be referenced in a data file either as a whole or element by element. Thus _a.vec being defined as an array or list in CIF2 would automatically make the tags _a.vec[1] _a.vec[2] ... defined CIF2 tags. If the array or list were nested, the _a.vec[1][1] _a.vec[1][2] etc. would be valid tags I would propose that this be general and automatic, applying to all tags defined as list or arrays. In view of past practice in CIF1, there is a slight conflict with respect to the default starting index in dREL versus the common CIF1 practice in indexing arrays from 0, but that can (and should be solved) with explicit specification of a starting index, so we can carry over the tag name usage from CIF1 without confusing people with an index shift. So, if _a.vec were an array of dimension 5, starting from index 0, _a.vec[0] through _a.vec[4] would be valid, but if the starting index were specified as 1, _a.vec[1] through _a.vec[5] would be valid, matching CIF1 conventions. The aliasing mechanism might have to be extended or clarified to handle the mapping against CIF1 tags in bulk for _a.vec as a whole, but, to me, this has a very intuitive feel. Regards, Herbert At 3:29 PM -0500 12/9/09, John Westbrook wrote:Hi all - On the issue of reserved characters in mmCIF/PDBx data items, these generally have been inherited from the style of items from the core. The majority of items in this class are data items related to short matrices/tensors and vectors (e.g. items including []). Virtually all have a syntax which could reasonably be interpreted as a programmatic reference. For instance, _atom_sites.fract_transf_matrix[1][1] 0.007738 _atom_sites.fract_transf_matrix[1][2] 0.000000 _atom_sites.fract_transf_matrix[1][3] 0.004298 _atom_sites.fract_transf_matrix[2][1] 0.000000 _atom_sites.fract_transf_matrix[2][2] 0.016545 _atom_sites.fract_transf_matrix[2][3] 0.000000 _atom_sites.fract_transf_matrix[3][1] 0.000000 _atom_sites.fract_transf_matrix[3][2] 0.000000 _atom_sites.fract_transf_matrix[3][3] 0.020200 _atom_sites.fract_transf_vector[1] 0.00000 _atom_sites.fract_transf_vector[2] 0.00000 _atom_sites.fract_transf_vector[3] 0.00000 Are we close to being able to treat these as legal in the context of CIF2/DDL+? I suppose I am asking what will constitute a legal assignment for an element of a matrix/array - Only this - _a.vec [1,2,3] or also expanded assignment by element such as - _a.vec[1] 1 _a.vec[2] 2 _a.vec[3] 3 If the latter is to be considered, then this will solve most of the data name issues for our data. Regards, John Joe Krahn wrote:In practice, CIF2 parsers should allow CIF1 data names within a CIF2 formatted file. The question is whether these files should be allowed as valid CIF2, or just for convenience as a non-standard CIF2. When CIF files are used as working data files, the restrictions should be relaxed. For long-term archival files, it makes sense to be more restrictive. I would just make the CIF1 names inaccessible to dREL. Alternatively, an implementation could allow CIF1 names only on reading, and require dictionary alias mappings to CIF2 names. One argument in favor of allowing them would be that someone wants to convert all data files to CIF2 format, but they want to preserve the original data as-is, without alias mapping. I think that the current CIF2 syntax makes it possible to use CIF1 names without any ambiguities. The question is whether they should be considered valid CIF2, or just a non-standard version that will be useful for the transitional period. Joe Herbert J. Bernstein wrote:Personally, I would greatly prefer to allow all data names that do not create a major lexer/parser conflict to appear in a data CIF and only apply the strong restrictions to data names that appear in CIF2 dictionaries as defined data names (not as aliases). -- Herbert At 2:40 PM +0000 12/9/09, Brian McMahon wrote:I have one remaining niggle that I'd like to revisit before we put this finally to bed. As has been mentioned a couple of times recently, restricting the data-name character set does invalidate syntactically many existing CIF 1 files (e.g. _refine_ls_shift/esd_max ). We have discussed strategies for handling this, and I think these are workable strategies, but will involve investment and hence expense in workflow management in CIF archives. I understand the rationale behind this restriction is to simplify future processing of data names in areas such as dREL applications. The question really is whether we're choosing the right trade-off in making things cleaner at that end of the processing chain. I would suppose that a dREL or other application could ingest a data name with dangerous characters, convert it internally into a "safe" identifier that's used for all processing, and then restore the original form upon output; but writing that intermediate layer of processing is of course expensive (especially if there aren't readily available libraries that will do this transparently). I suspect that some of the original proposed syntactic changes also had the effect (whether by design or collaterally) of simplifying i/o, data structure management, symbol table processing etc., but those may have suffered in the subsequent revision exercise we've just been practising. Given the consensus we are now approaching, would the code builders now be prepared to incur the addition expense of handling "dangerous" data names? I really don't want to spark off a long discussion on this - if a quick round of response shows that there's no appetite to allow the additional punctuation characters in data names, I'll accept that gracefully. *** One last comment while I have the floor, though it is related in part to the above question. A concern raised in the editorial office was that there would be circumstances where users didn't know if they were dealing with a CIF 1 or 2 ("users" meaning authors, perhaps resorting to the vi editor - and we're imagining most of them are dealing with small-molecule/inorganic CIFs). My supposition is that the IUCr editorial offices would only want to use CIF2 seriously in association with DDLm dictionaries, and that we would expect the revised core dictionaries to use the dot component in data names to signal this further evolution. So even a superficial glimpse of the middle of a CIF would make it clear whether it was CIF1 or CIF2. Does that fit in with how others see this progressing? Cheers Brian _______________________________________________ ddlm-group mailing list ddlm-group@iucr.org http://scripts.iucr.org/mailman/listinfo/ddlm-group_______________________________________________ ddlm-group mailing list ddlm-group@iucr.org http://scripts.iucr.org/mailman/listinfo/ddlm-group-- ****************************************************************** John Westbrook, Ph.D. Rutgers, The State University of New Jersey Department of Chemistry and Chemical Biology 610 Taylor Road Piscataway, NJ 08854-8087 e-mail: jwest@rcsb.rutgers.edu Ph: (732) 445-4290 Fax: (732) 445-4320 ****************************************************************** _______________________________________________ ddlm-group mailing list ddlm-group@iucr.org http://scripts.iucr.org/mailman/listinfo/ddlm-groupcheers Nick -------------------------------- Associate Professor N. Spadaccini, PhD School of Computer Science & Software Engineering The University of Western Australia t: +61 (0)8 6488 3452 35 Stirling Highway f: +61 (0)8 6488 1089 CRAWLEY, Perth, WA 6009 AUSTRALIA w3: www.csse.uwa.edu.au/~nick MBDP M002 CRICOS Provider Code: 00126G e: Nick.Spadaccini@uwa.edu.au _______________________________________________ ddlm-group mailing list ddlm-group@iucr.org http://scripts.iucr.org/mailman/listinfo/ddlm-groupcheers Nick -------------------------------- Associate Professor N. Spadaccini, PhD School of Computer Science & Software Engineering The University of Western Australia t: +61 (0)8 6488 3452 35 Stirling Highway f: +61 (0)8 6488 1089 CRAWLEY, Perth, WA 6009 AUSTRALIA w3: www.csse.uwa.edu.au/~nick MBDP M002 CRICOS Provider Code: 00126G e: Nick.Spadaccini@uwa.edu.au _______________________________________________ ddlm-group mailing list ddlm-group@iucr.org http://scripts.iucr.org/mailman/listinfo/ddlm-groupcheers Nick -------------------------------- Associate Professor N. Spadaccini, PhD School of Computer Science & Software Engineering The University of Western Australia t: +61 (0)8 6488 3452 35 Stirling Highway f: +61 (0)8 6488 1089 CRAWLEY, Perth, WA 6009 AUSTRALIA w3: www.csse.uwa.edu.au/~nick MBDP M002 CRICOS Provider Code: 00126G e: Nick.Spadaccini@uwa.edu.au _______________________________________________ ddlm-group mailing list ddlm-group@iucr.org http://scripts.iucr.org/mailman/listinfo/ddlm-group |
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