The ROWSPEC itself is indeed static, but depending on how you plan to use/expose this, you might generate/write a SELECT statement that does the renaming:

SELECT GLCode, Description, Year1 AS Jul2017, Year2 AS Jul2018 
FROM MyPackage.MyClass_GLReportYearToYearTrend(2017)

I just realized you're only on Caché 2012, which doesn't support table-valued functions, in which you can just SELECT from a function rather than having to use CALL, sorry.

On the other hand, I'd expect a BI tool like Logi to be capable of providing exactly the sort of UI-side labelling of columns, if not drive the entire YoY calculation. Not that I want to fend off the question, but if there's a full-fledged BI tool sitting on top of these results anyhow, let's make sure to use its full set of fledges :-) 

Hi Joe,

would you mind sharing some of your code (minus API key values :-) ) for signing AWS REST calls? I have almost scratched my head off trying to find out why things still aren't working when my StringToSign and SigningKey appear to be correct, but the hash I create from them isn't. I can even reproduce (aka "make the same mistake") using the sample Python code AWS provides.

Relevant but not working (and therefore less relevant) code:

Property AWSAccessKeyId As %String [ InitialExpression = "AKIDEXAMPLE" ];Property AWSSecretAccessKey As %String [ InitialExpression = "wJalrXUtnFEMI/K7MDENG+bPxRfiCYEXAMPLEKEY" ];Property Region As %String [ InitialExpression = "us-east-1" ];Property Service As %String [ InitialExpression = "iam" ];Method BuildAuthorizationHeader(pHttpRequest As %Net.HttpRequest, pOperation As %String = "", pURL As %String = "", Output pAuthorizationHeader As %String, pVerbose As %Boolean = 0) As %Status{set tSC = $$$OKtry {if ..AWSAccessKeyId="" {set tSC = $$$ERROR($$$GeneralError, "No AWS Access Key ID provided")quit}if ..AWSSecretAccessKey="" {set tSC = $$$ERROR($$$GeneralError, "No AWS Secret Access Key provided")quit}set tAMZDateTime = $tr($zdatetime($h,8,7),":") // 20190319T151009Z//set tAMZDateTime = "20150830T123600Z" // for AWS samplesset tAMZDate = $e(tAMZDateTime,1,8) // 20190319set tLineBreak = $c(10)set pOperation = $$$UPPER(pOperation)// ensure the right date is setdo pHttpRequest.SetHeader("X-Amz-Date", tAMZDateTime)// ************* TASK 1: CREATE A CANONICAL REQUEST *************// http://docs.aws.amazon.com/general/latest/gr/sigv4-create-canonical-request.html// Step 1 is to define the verb (GET, POST, etc.) -- inferred from pOperation// Step 2: Create canonical URI--the part of the URI from domain to query // string (use '/' if no path)set tCanonicalURL = $s($e(pURL,1)="/":pURL, $e(pURL,1)'="":"/"_pURL, 1:"/"_pHttpRequest.Location)// Step 3: Create the canonical query string. In this example (a GET request),// request parameters are in the query string. Query string values must// be URL-encoded (space=%20). The parameters must be sorted by name.// For this example, the query string is pre-formatted in the request_parameters variable.set tQueryString = $piece(tCanonicalURL,"?",2,*)set tCanonicalURL = $piece(tCanonicalURL,"?",1)// TODO: append pHttpRequest.Params content?// TODO: sort params!// Step 4: Create the canonical headers and signed headers. Header names// must be trimmed and lowercase, and sorted in code point order from// low to high. Note that there is a trailing \n.set tCanonicalHeaders = "content-type:" _ pHttpRequest.ContentType _ tLineBreak_ "host:" _ pHttpRequest.Server _ tLineBreak_ "x-amz-date:" _ tAMZDateTime _ tLineBreak// Step 5: Create the list of signed headers. This lists the headers// in the canonical_headers list, delimited with ";" and in alpha order.// Note: The request can include any headers; canonical_headers and// signed_headers lists those that you want to be included in the // hash of the request. "Host" and "x-amz-date" are always required.set tSignedHeaders = "content-type;host;x-amz-date"// Step 6: Create payload hash (hash of the request body content). For GET// requests, the payload is an empty string ("").if (pOperation = "GET") {set tPayload = ""} else {// TODOset tPayload = ""}set tPayloadHash = ..Hex($SYSTEM.Encryption.SHAHash(256,$zconvert("","O","UTF8")))// Step 7: Combine elements to create canonical requestset tCanonicalRequest = pOperation _ tLineBreak_ tCanonicalURL _ tLineBreak_ tQueryString _ tLineBreak_ tCanonicalHeaders _ tLineBreak _ tSignedHeaders _ tLineBreak_ tPayloadHashset tCanonicalRequestHash = ..Hex($SYSTEM.Encryption.SHAHash(256, tCanonicalRequest))w:pVerbose !!,"Canonical request:",!,$replace(tCanonicalRequest,tLineBreak,"<"_$c(13,10)),!!,"Hash: ",tCanonicalRequestHash,!// ************* TASK 2: CREATE THE STRING TO SIGN*************// Match the algorithm to the hashing algorithm you use, either SHA-1 or// SHA-256 (recommended)set tAlgorithm = "AWS4-HMAC-SHA256"set tCredentialScope = tAMZDate _ "/" _ ..Region _ "/" _ ..Service _ "/" _ "aws4_request"set tStringToSign = tAlgorithm _ tLineBreak _ tAMZDateTime _ tLineBreak _ tCredentialScope _ tLineBreak_ tCanonicalRequestHashw:pVerbose !!,"String to sign:",!,$replace(tStringToSign,tLineBreak,$c(13,10)),!// ************* TASK 3: CALCULATE THE SIGNATURE *************// Create the signing key using the function defined above.// def getSignatureKey(key, dateStamp, regionName, serviceName):
     set tSigningKey = ..GenerateSigningKey(tAMZDate)
     w:pVerbose !!,"Signing key:",!,..Hex(tSigningKey),!// Sign the string_to_sign using the signing_keyset tSignature = ..Hex($SYSTEM.Encryption.HMACSHA(256, tStringToSign, tSigningKey))// ************* TASK 4: ADD SIGNING INFORMATION TO THE REQUEST *************// The signing information can be either in a query string value or in // a header named Authorization. This code shows how to use a header.// Create authorization header and add to request headersset pAuthorizationHeader = tAlgorithm _ " Credential=" _ ..AWSAccessKeyId _ "/" _ tCredentialScope _ ", SignedHeaders=" _ tSignedHeaders _ ", Signature=" _ tSignaturew:pVerbose !!,"Authorization header:",!,pAuthorizationHeader,!!b} catch (ex) {set tSC = ex.AsStatus()}quit tSC}Method GenerateSigningKey(pDate As %String) As %String{set kDate = $SYSTEM.Encryption.HMACSHA(256, pDate, $zconvert("AWS4" _ ..AWSSecretAccessKey,"O","UTF8"))
    //w !,"kDate: ",..Hex(kDate)
    set kRegion = $SYSTEM.Encryption.HMACSHA(256, ..Region, kDate)
    //w !,"kRegion: ",..Hex(kRegion)
    set kService = $SYSTEM.Encryption.HMACSHA(256, ..Service, kRegion)
    //w !,"kService: ",..Hex(kService)
    set tSigningKey = $SYSTEM.Encryption.HMACSHA(256, "aws4_request", kService)
    //w !,"kSigning: ",..Hex(tSigningKey),! quit tSigningKey}ClassMethod Hex(pRaw As %String) As %String [ Internal ]{set out="", l=$l(pRaw)for i = 1:1:l {set out=out_$zhex($ascii(pRaw,i))}quit $$$LOWER(out)}ClassMethod SimpleTest() As %Status{set tSC = $$$OKtry {set tAdapter = ..%New()set tAdapter.AWSAccessKeyId = "use yours"set tAdapter.AWSSecretAccessKey = "not mine"set tAdapter.Region = "us-east-1", tAdapter.Service = "iam"set tRequest = ##class(%Net.HttpRequest).%New()set tRequest.ContentType = "application/x-www-form-urlencoded"set tRequest.ContentCharset = "utf-8"set tRequest.Https = 1set tRequest.SSLConfiguration = "SSL client" // simple empty SSL configset tRequest.Server = "iam.amazonaws.com"set tURL = "/?Action=ListUsers&Version=2010-05-08"set tSC = tAdapter.BuildAuthorizationHeader(tRequest, "GET", tURL, .tAuthorization, 1)quit:$$$ISERR(tSC)set tRequest.Authorization = tAuthorizationset tSC = tRequest.Get(tURL)quit:$$$ISERR(tSC)Do tRequest.HttpResponse.OutputToDevice()} catch (ex) {set tSC = ex.AsStatus()}write:$$$ISERR(tSC) !!,$system.Status.GetErrorText(tSC),!quit tSC}